Black Legion

"Let the galaxy burn!"

- The Warmaster Horus

The Black Legion is a a Traitor Legion of Chaos Space Marines that is the first in infamy, if not in treachery, whose name resounds as a curse throughout the scattered and war-torn realms of humanity. The Black Legion was one of the 9 First Founding Legions of Space Marines who turned Traitor to the Imperium during the Horus Heresy in the early 31st Millennium. The Black Legion became the primary instrument of its Primarch, the Warmaster Horus, to overthrow the Emperor of Mankind and seize control of the Imperium in the name of Chaos. Such are the crimes of the Black Legion that it is easy to forget that the past was very different, and that there was a time when its Astartes and their perfidious master Horus were lauded above all of the other warriors of the Legiones Astartes, and were considered the most favoured servants of the Emperor of Mankind. Born as the XVI Space Marine Legion on Terra, the Black Legion would first rise to greatness under the name of the Luna Wolves. Before the dark days of the Horus Heresy they fought at the Emperor’s side on Terra and through the early years of the Great Crusade. They were as stalwart and indefatigable as any of the servants of the Emperor and their actions exemplified what it meant to be a warrior of the Space Marine Legions. Brutal, ruthless and unwavering but also honourable, and once loyal beyond question, the history of the Black Legion is the history of the ambition of the Imperium itself, and the flaws that broke its founder's dreams of unification and glory for all Mankind asunder.

The Black Legion is now one of the Traitor Legions of Chaos Space Marines who are united in the pursuit of the single purpose of overthrowing the Imperium. They oppose the infighting that consumes so many of their brethren amongst the other Traitor Legions, for the Astartes of the Black Legion are the greatest servants of Chaos Undivided. They are always brought together in great numbers to work the will of their Warmaster, Abaddon the Despoiler, the heir of Horus. Whenever the entirety of the Black Legion is called to battle, it marks the beginning of another one of Abaddon's Black Crusades against the Imperium of Man.

The Black Legion is the only one of the Traitor Legions to have changed its name following the Horus Heresy. The XVI Legion was originally known as the Luna Wolves during the Great Crusade. In honour of Horus' great achievements during the latter years of that era after the Imperial victory over the Orks during the Ullanor Crusade, the Emperor suggested that the Legion be renamed the Sons of Horus. Horus eventually instituted this change following his conversion to the service of the Dark Gods of Chaos on the world of Davin. After Horus' treachery and final defeat at the Battle of Terra during the Horus Heresy, however, the Legion was renamed the "Black Legion" by its new Warmaster, Abaddon the Despoiler. The new name was chosen after the Astartes of the Sons of Horus painted their Power Armour black in grief at the death of their Primarch Horus and shame at their failure to overthrow the False Emperor and seize control of the galaxy in the name of the Ruinous Powers.

The Wolves of Terra
In the time when the Emperor's eye first began to fall beyond Terra, he raised new armies to fight his Great Crusade. He drew these new troops in part from the forces that had already unified Terra during the Unification Wars of the late 30th Millennium, from willing Terran volunteers like those who comprised the XVI Space Marine Legion who were implanted with the gene-seed of their missing Primarch Horus like all the Astartes of the First Founding. These recruits were also drawn in part from the Emperor's subjugated enemies, and together they represented the first generation of Space Marines. Like most of the embryonic Space Marine Legions, the XVI Legion drew all of its first recruits from the Terran population. Though it is difficult to be certain based on the existing Imperial records from this lost time, there are indications that many of the XVI Legion’s early intake came from the hunter clans of the Jutigran Bowl and the Samsatian sub-plate slums. Perpetual conflict and the harshness of life on the desolate margins of Terran society had given these people the hard edge of ruthlessness and independence that would serve a Space Marine well.

The XVI Legion made war with abrasive aggression. Perhaps through the influence of their genetic heritage or the use the Emperor put them to, the Space Marines of the XVI Legion became synonymous with sudden and overwhelming shock assaults. To the XVI Legion fell the swift prosecution of battle and the bloody termination of campaigns. Their attacks were preemptive as often as they were part of an existing conflict, their forces either the first deadly threat unleashed by the Imperium or preserved to enact a final, killing blow. The First Pacification of Luna was perhaps the most famous of these early victories for the XVI Legion, but the breaking of the Coriolis Enclaves and the Five Winter left scars in the collective consciousness of Terran society that persist even now. In the Capridian Sinks, it is still common for traders and gamblers to refer to the Legion’s ancient number of sixteen as "the counting of the wolf."

It is said that the Astartes of the XVI Legion were unleashed to begin and end wars their enemies did not even know they were fighting. They would come out of the night or in the dawn, carried in the holds of Stormbirds and Storm Eagles, flanked by squadrons of escorting Lightning Crows. Those who witnessed such attacks say that the XVI Legion were fighting eye-to-eye with the enemy before the thunder of their first volley of missiles and shell-strikes had faded. The warriors who fought these battles were of a character wholly in keeping with their reputation. Proud, little given to humour or empathy, nor to mysticism or even the ritual of the military elite, they were a breed apart from the true human forces that had fought at their side. Their aggression was clear in their every action, but so was the strength of the control that held it in check, and the needs of that ancient age easily accommodated such a belligerent and cantankerous attitude.

At some time the notion of the Emperor sending his "wolves" to break intractable or potential enemies took root in the consciousness of the new-born Imperium of Man, with the Pacification of Luna in the late 30th Millennium -- considered by many the first battle of the Great Crusade -- its apocryphal source. The XVI Legion embraced the epithet "Luna Wolves" they earned after this first campaign with relish. The wolf's head became a common icon for the Astartes of the XVI Legion, the link being somewhat abstract, as the Terran animals once called wolves had been almost extinct for millennia, largely relegated to existence as gene-stock for engineered bio-weapon beasts on Terra itself, though the name remained synonymous in most Terran dialects with controlled savagery. The wearing of pelts of such augmented canid predators increasingly marked out the field commanders and officers of the Luna Wolves. The XVI would not be the only Space Marine Legion to bear such a title and embrace this imagery as their own, but they were the first.

Cthonia
The Luna Wolves were the first Space Marine Legion to begin recruiting from another world beyond Terra. In this case, the new pool of Aspirants was found amongst the adolescent human males drawn from the violent hive city gangs inhabiting an ancient former Mining World that had devolved into a Feral World called Cthonia. Cthonia was located in one of Terra's closest neighbouring star systems in the Segmentum Solar and was within reach of spacecraft that could travel at only sublight velocities before the invention of the Warp-Drive. As a result, Cthonia had been colonised, built upon, tunnelled and mined since the dawn of human interstellar space travel millennia before the beginning of the Dark Age of Technology. Due to this unusually long period of exploitation by Mankind, all of the world's natural resources had been stripped away and used up centuries before, and the ancient mining technology had long since been rediscovered and removed by the Tech-adepts of Mars. The planet that remained was largely useless and abandoned, completely riddled with catacombs, crumbling industrial plant and exhausted mine-workings.

Horus Lupercal
Horus, the true Primarch of the Luna Wolves, was the first of the Primarchs to be recovered by the Emperor, having been cast in his gestation capsule through the Warp much closer to Terra on Cthonia than the others by the Ruinous Powers, and he was found at a much younger age. Whereas the early history of many Primarchs is extensively if unevenly documented, the same cannot be said of Horus. Contradiction and omission tarnishes all accounts of Horus' formative years. It is clear that the Emperor did find Horus and also that he took command of the XVI Legion early in the Great Crusade. Beyond these manifest facts, agreement between the early Imperial sources is decidedly lacking, some even placing Horus on Cthonia as a foundling. Like many of his superhuman brethren, these sources say that the young Primarch thrived in Cthonia's harsh environment, learning his first lessons in war and killing from Cthonia's tech-barbarian kill-gangs. Another source claims that Horus returned to Terra itself. It is said that Horus grew at the Emperor's side, learning from his father even as they took back the Sol System and forged the alliances between the techno-barbarian nations of Terra and with the Mechanicus of Mars that created the Imperium of Man. Other highly creditable claims state that the Emperor found Horus, the first of his lost sons, but neither source specifies where, or the location of this finding. Surrounded in millennia of myths and allegory, the truth of Horus' origins will more than likely never be known. As a result, Horus was for many standard years the Emperor's only son, and there was a great affinity between them. The Emperor spent much time with his protege, teaching and encouraging him. Horus was soon placed in command of the XVI Legion, which had already come to be known as the Luna Wolves -- 10,000 Astartes created from his own genetic code. With these superhuman warriors to lead, Horus accompanied the Emperor for the first thirty standard years of the Great Crusade that had begun in ca. 800.M30, and together they forged the initial interstellar expansion of the young Imperium of Man.

A Human Harvest
By the time the Great Crusade began in circa 800.M30, Cthonia's mines were long spent, but it had a resource that the new Imperium needed more than metals and jewels: hardened fighters and born survivors in their millions; a lean and hungry race of killers with no illusions about the horrors of the universe. Cthonia, relatively close to Terra in the void, and with whom some minor intermittent contact had been maintained even through the Age of Strife, had its murderous and strife-torn population marked by one of the first Expeditionary Fleets to leave the Sol System. To fuel the growth of the early Space Marine Legions, the Imperium took full advantage of the bounty that Cthonia provided. At the time of the First Founding, Cthonia already helped provide the necessary flesh for the Selenar gene-wrights of Luna to fuel the growth of the early Legiones Astartes. One report talks of so-called Imperial "recruitment squads" harvesting tens of thousands of Cthonian gangers and shipping them away, chained together in the holds of prison-shuttles, to the geno-laboratories of Luna's Selenar gene-wrights. The majority were impressed as troopers for the Great Crusade's Imperial Army regiments, but the finest specimens were taken for induction into Space Marine Legions. On Luna these chosen sons of Cthonia were reborn as the superhuman Astartes of the XVI Legion. It was more common for the first Space Marine Aspirants to be adolescent volunteers from Terra, and later in the Crusade, after the rediscovery of the Primarchs, from Feral or Feudal Worlds. Yet, after the usual psycho-hypnotic indoctrination and mental conditioning process, the Luna Wolves created from the men of Cthonia emerged as excellent and ferociously powerful Space Marines.

A Legion Reborn
With the induction of the genestock from Cthonia, the XVI Legion was remade. For the Terran Space Marines who already constituted the core of the Legion, their new brothers brought with them their own customs, attitudes and modes of thought, the ingrained inheritances of a thousand generations of callous violence and the ruthless pursuit of survival that the indoctrination practices of the time could modify and perhaps suppress but not entirely erase, which was perhaps the point for the Cthonians' inclusion within the Legion. As the Terran Legionaries fell in battle, their voices and the more ordered military traditions they had been trained in became fewer and fainter within the XVI Legion. The marks of change were many and subtle, not overwriting entirely the Legion's culture but bringing a unique character to what had gone before. Examples of this change came slowly. The topknots and mohawks commonly sported by Cthonian ganger head-hunters became common throughout the ranks of the Luna Wolves as both additions to their armour and as personal decoration. After being wounded in battle by a worthy foe it was common for a Luna Wolf Astartes to honour the valour of his fallen enemy by making a deep scratch in the ceramite across his helm's eye socket. Perhaps most tellingly, the Cthonian word for cutting the throat of an enemy gang-killer in single combat -- "aebathan" -- became a common term in the ranks to describe the completion of a campaign. The personal charisma and reputation of a commander within the Legion came to apply to the Astartes under his command, as if the ways of the Cthonian gang lords now informed the Luna Wolves' own understanding of leadership. This applied particularly to the Luna Wolves' Primarch Horus after his redicovery by the Emperor, as his cult of personality was universal within the Legion and all Luna Wolves came to revere the Lupercal to an extent that would ultimately prove their undoing.

The strength of the Luna Wolves in battle did not change or weaken after the inclusion of the Cthonians; if anything the Legion seemed to become even more potent over time. The Legion strove to maintain the required flexibility needed to allow them to fight any war or enemy they might encounter on their own terms, but where possible the application of sudden and overwhelming force was usually their favoured form of attack, and that of their Primarch. As a doctrine this became bound up with the Legion's savage ferocity that was born of Cthonian blood, and wielded with ferocious intelligence and the matchless tactical instinct of Horus. A star system targeted for Imperial Compliance would often fall to the Legion in a single engagement: Luna Wolves warships would cut in from the system's edge, forming a spear formation that would break into many smaller blade tips to strike at the target system's planets, moons and space stations. Orbital bombardment and simultaneous mass orbital drops would break the enemy's strength and will to resist. Tactical threats were systematically identified, isolated, outflanked, encircled and destroyed with merciless precision and close-quarter savagery which spoke of apex pack predators splitting a herd and gutting its members with lightning fury. The Imperial Army troops that followed in the Luna Wolves' wake often had little to do but scrape suddenly Compliant worlds clean of the leavings of battle.

Sons of Victory
The Luna Wolves' approach to the Great Crusade was direct and brutal, and their results were often inelegant if unmistakably effective. Though it proved bloody, the XVI Legion's progress was undoubtedly swift and laurels of victory were heaped upon the Luna Wolves and above all upon their Primarch Horus, the most beloved son of the Emperor. Time and again, the Luna Wolves would break resistance on a world and move on to the next campaign with barely a backward glance. The character of the Luna Wolves' tenacity and ruthlessness was displayed during the initial Imperial conquest of the Sol System. They prosecuted battles with the same savage mentality and ferocity displayed during the gang-wars of Cthonia where prisoners were simply unwanted mouths to feed. War was a matter of identifying the strength and leadership of the enemy, isolating it and then obliterating it. In the same way that a gang leader's eyes would find a rival and their knife would quickly follow, so the Luna Wolves conquered entire star systems. Brutal it might have been, but to the Space Marines of the Luna Wolves it was a matter of necessity; wars were either brutal and short or they became long and wasteful. Driven by the energy of the Great Crusade, the XVI Legion's methods fitted the needs of the Imperium's rapid expansion.

The Luna Wolves waged war during the Great Crusade for over 200 standard years until the dawn of the 31st Millennium, pushing back the darkness which had swallowed mankidn during the Age of Strife with fire and blood. Their victories were manifold and Horus' generalship was legend, and so it was that the respect of their brother Legions rose to almost unrivalled heights. Across tens of thousands of battles the Luna Wolves were rarely defeated. In every mode of deployment they excelled, whether as the spearhead of a star cluster-sized assault or as an individual squad supporting a grand formation of the Imperial Army. Other Legions, sometimes hostile to the interference of their fellow Space Marines, would request campaign placement amongst the Luna Wolves and welcome it in return.

Much of the Luna Wolves' reputation was the reflection of the qualities of their Primarch. Horus' charisma and unequalled record of victories, as well as his known closeness to the Emperor, lent him a measure of respect unrivalled among his brother Primarchs. Horus demonstrated an almost preternatural talent for wielding the relative strengths of the other Legions to their best advantage on a strategic level. Horus was said by some to be without peer as a commander and a ruler within the Imperium, surpassed only by the Emperor Himself. Certainly he was rare amongst the Primarchs in that Horus commanded the respect and the loyalty of all, and backed it up with strategic and tactical genius. Others commanded larger Legions, saw more deeply, excelled beyond Horus in certain crafts of warfare and lore, or perhaps drew greater fraternal affection from his Astartes, but only Horus could hold every view and ideal of Mankind in his mind simulataneously. Even the most difficult and aggressive of Primarchs like Angron and Konrad Curze are known to have deferred to Horus on many matters.

Triumph of Ullanor
"You are like a son and together we have all but conquered the galaxy. Now the time has come for me to retire to Terra. My work as a soldier is done and now passes to you for I have great tasks to perform in my earthly sanctum. I name you Warmaster and from this day forth all of my armies and generals shall take orders from you as if the words came from mine own mouth. But words of caution I have for you, for your brother Primarchs are strong of will, of thought and of action. Do not seek to change them, but use their particular strengths well. You have much work to do, for there are still many words to liberate, many peoples to rescue. My trust is with you. Hail Horus! Hail the Warmaster!"

- The Emperor of Mankind, during the Triumph of Ullanor

Though the Luna Wolves had won many victories in their years of ceaseless conflict, one would eclipse all others and see them reborn once again. The greatest of the nascent Imperium's victories during the high point of the Great Crusade came in the form of the defeat of the largest Ork empire ever encountered. The Ullanor Crusade was a vast Imperial assault on the Ork empire of the Overlord Urrlak Urruk. The capital world of this Greenskin stellar empire, and the site of the final assault by the Space Marine Legions, lay in the central Ullanor System of the galaxy's Ullanor Sector. The Crusade included the deployment of 100,000 Space Marines, 8,000,000 Imperial Army troops, and thousands of Imperial starships and their support personnel. The Ullanor Crusade marked the high point of the Great Crusade's vast effort to reunite the scattered colony worlds of humanity. The Orks of Ullanor represented the largest concentration of Greenskins ever defeated by the military forces of the Imperium of Man before the Third War for Armageddon began during the late 41st Millennium. Following the defeat of the Orks of Ullanor, the Emperor of Mankind returned to Terra to begin work on his vast project to open up the Eldar Webway for Mankind's use. In his place to command the vast forces of the Great Crusade he left Horus. In the aftermath of this Ullanor Crusade, Horus was granted the newly-created title of “Warmaster”, the commander-in-chief of all the Emperor’s armies who possessed command authority over all of the other Primarchs and every Expeditionary Fleet of the Great Crusade. Before returning to Terra to oversee the next phase of the creation of his stellar empire, the Emperor suggested to Horus that he rename the XVI Legion the "Sons of Horus," in honour of their Primarch and to show his preeminent place amongst the other Primarchs. Horus initially declined this honour, not wishing to be set above his brothers, and so his Legion continued as the Luna Wolves for a little while longer. But Horus and the other Primarchs never came to terms with the Emperor's absence. Their hurt feelings over his seeming abandonment of the Great Crusade to pursue a secret project whose purpose he chose not to reveal to his sons laid the seeds of jealousy and resentment that would ultimately blossom into the corruption that begat the Horus Heresy.

Warmaster
During the Great Crusade, it became apparent that the Primarchs were far from the perfect specimens of humanity they were intended to be. Although each Primarch was physically and mentally god-like compared to a baseline mortal human being, they harboured the flaws of vanity, egotism, hunger for power, jealousy, arrogance, insecurity and all the other sins of the human character. As the Imperial Warmaster, Horus took over command of the Great Crusade, and accepted his new duties with earnest dedication. However, there was much dissension in the ranks of the Primarchs and other parties in the Imperium over the Emperor's decision to withdraw from the campaign and return to Terra as well as to reorganise the political administration of the Imperium under the control of a Council of Terra headed by his regent, Malcador the Sigillite. Only a handful of the Primarchs, amongst them a scheming Lorgar, remained steadfast beside the Warmaster during this period of conflict. Horus also disagreed with many of the decrees passed by the newly established Council of Terra, a ruling body of Imperial nobles and bureaucrats, which were intended to shift the burden of taxation and administration onto the newly-conquered Imperial Compliant worlds. Even worse, Horus came to believe in his heart that he was failing his father, and was deeply wounded that the Emperor had revealed to none of the Primarchs, not even his most favoured son, why he had secluded himself upon Terra and the truth behind his secret Imperial Webway Project. These seeds of bitterness, resentment and frustration grew, and would soon bear deadly fruit.

Fall to Chaos
It was on the moon of the world of Davin that Horus' fate was sealed. This was the second time his Legion had been posted to this world; after the previous visit sixty standard years earlier the Luna Wolves had adopted the native Davinite institution of warrior lodges. Though these lodges had begun as simple fraternities of warriors, their secretive nature handed Lorgar, the Primarch of the Word Bearers Legion and his First Chaplain Erebus, the tool they needed to manipulate Horus towards the service of the Chaos Gods. Lorgar and his Word Bearers originally came from Colchis, a world defined by religious fanaticism. They had long worshiped the Emperor as a god. The Word Bearers had sought to spread their Cult of the Emperor to every world they added to the Imperium. But the Emperor deeply disliked and mistrusted organised human religion (ironic, since he had often been the focus for much of it in his various guises across history), blaming it for much of the darkness that had plagued humanity's history. The Emperor openly and publicly refuted his alleged divinity and banned religious worship in his empire, and demanded that his subjects accept the "Imperial Truth"-- that science, reason and logic alone presented the tools required to create a better human future. Lorgar did not suffer the Emperor's reprimand or views on religion well after his XVII Legion had been humilated by the Ultramarines Legion on the direct orders of the Emperor at the world of Khur. Angered and wounded that the Emperor would not accept his devotion and worship, Lorgar began what became known as the Pilgrimage of Lorgar to discover the truth of divinity in the universe. This quest ultimately culminated in Lorgar turning to the service of the Ruinous Powers of the Warp -- Dark Gods who were all too willing to accept the devotion of one of humanity's Primarchs. Before long, the Word Bearers Legion had been almost entirely corrupted by the Chaos Gods, and Lorgar and the XVII Legion's First Chaplain Erebus were tasked by the Ruinous Powers with corrupting all of their fellow Space Marines -- starting with the greatest of them all, the Warmaster Horus.

During a battle against Chaos-spawned undead on Davin's moon, whose Planetary Governor, Eugen Temba, a former Imperial Army commander, had been corrupted by the forces of the Chaos God Nurgle, Horus was poisoned by a xenos blade dedicated to Nurgle known as a Kinebrach Anathame that had been stolen from the human civilisation of the Interex by Erebus after Horus and the Luna Wolves of the 63rd Expeditionary Fleet had made a disastrous first contact with them. Erebus then gifted the weapon to the Chaos-corrupted form of Temba who the Warmaster had left behind on the Feral World of Davin sixty Terran years before. Temba had turned to the worship of Nurgle in the interim, being transformed into a bloated mutant and killing off most of his Imperial Army garrison in the process, transforming them into undead Plague Zombies that the Luna Wolves were forced to mow down in waves. Horus personally faced off with the Nurgleite mutant that had been Temba aboard the grounded ruins of his Imperial Cruiser. In the course of that battle, the potent living metal of the Chaos blade wielded by that plague-infused monstrosity left Horus with a bleeding, toxic wound in his shoulder that his Legion's Apothecaries could not heal despite all the advanced technology available to them. Sixty standard years earlier, when the Luna Wolves had brought about the successful Imperial Compliance of Davin, they had entrusted a detachment of the Word Bearers, under the command of its First Captain Kor Phaeron, to shepherd the people of Davin into the light of the Imperial Truth. At the suggestion of First Chaplain Erebus, the XVI Legion had adopted the native Davinite institution of "warrior lodges." Though these lodges had begun as simple fraternities of warriors, their secretive nature handed Lorgar and Erebus the tool they needed to manipulate Horus. Once formally introduced, these warrior lodges would infiltrate and eventually corrupt the various Space Marine Legions into turning against the Emperor. After the Warmaster was struck down on Davin's moon, Erebus saw his chance to further the designs of Chaos. The First Chaplain persuaded the Sons of Horus' warrior lodge to allow a group of Davinite shamans to heal Horus. In truth, these shamans were secretly a coven of Chaos Cultists known as the Serpent Lodge that had long been active on Davin at the temple dedicated to the Chaos Gods they called the Delphos. Desperate to save their beloved Primarch, the warrior lodge brothers acquiesced to Erebus's suggestions.

During the dark rituals that followed within the temple, Horus' spirit was transferred from his body into the Immaterium. There, he bore witness to a nightmare vision of the future. He saw the Imperium of Man as a repressive, violent theocracy, where the Emperor and several of his Primarchs (but not Horus) were worshipped as Gods by the masses. While this vision of the Imperial future granted by the Chaos Gods was a true one, it was ironically an outcome largely created by the Warmaster's own actions. The Dark Gods portrayed themselves as victims of the Emperor's psychic might, and claimed that they had no real interest in the happenings of the material world. Magnus the Red, the sorcerous Primarch of the Thousand Sons Legion, had also travelled into the Warp via sorcery to try and stop Horus from turning to Chaos. Magnus explained that the Warmaster's vision was only one among many possible futures, but one that Horus alone could prevent. Horus, already jealous and resentful of the Emperor, proved all too receptive to the Ruinous Powers' false vision. The Chaos Gods' pact with Horus was simple: "Give us the Emperor and we will give you the galaxy." Driven by his jealousy, desire for power and anger at what he saw as his father's abandonment of him, Horus accepted the Ruinous Powers' offer. They healed his grievous wound and filled him with the powers of the Warp. Renouncing his oath to the Emperor, Horus led his Legion, renamed the Sons of Horus, into worship of the myriad Chaos Gods in the form of Chaos Undivided. He then sought to turn many of his fellow Primarchs to the service of Chaos, and succeeded with Angron of the World Eaters, Fulgrim of the Emperor's Children and Mortarion of the Death Guard, who were the first of many to follow, along with many regiments of the Imperial Army and several Titan Legions of the Adeptus Mechanicus.

Magnus the Red, the Primarch of the Thousand Sons Legion, foresaw Horus' actions through his Legion's own use of forbidden psychic sorcery. Magnus then attempted to forewarn the Emperor of the impending betrayal of his favourite son. However, knowing that he would have to find a means of quickly warning the Emperor, Magnus used sorcery to send his message to the Emperor. The message penetrated the potent psychic defences of the Imperial Palace on Terra, shattering all the psychic wards the Emperor had placed on the Palace -- including those within his secret project in the Imperial Dungeons, where he was proceeding with the creation of the human extension into the Webway. Refusing to believe that Horus, his most beloved and trusted son, would actually betray him, the Emperor instead mistakenly perceived the traitor to the Imperium to be Magnus and his Thousand Sons, who had long suffered from a near-debilitating run of mutations because of the instability of Magnus' own genome and were known to have practiced the sorcery that had been expressly outlawed in the Imperium. The Emperor ordered the Primarch Leman Russ, Magnus' greatest rival, to mobilise his Space Wolves Legion and the witch hunters known as the Sisters of Silence and take Magnus into custody to be returned to Terra to stand trial for violating the Council of Nikaea's prohibitions against the use of psychic powers within the Imperium. While en route to the Thousand Sons Legion's homeworld of Prospero, Horus convinced Russ, who had always been repelled by Magnus' reliance on psychic powers, to launch a full assault on Prospero instead, even though Magnus had been entirely willing to face the Emperor's judgment once he realised he was being manipulated by the entities that called the Immaterium home.

Betrayal at Istvaan III
In the days that followed his miraculous recovery, Horus' officers detected a change in his character. The Warmaster proceeded to use the warrior lodge present in the XVI Legion to begin to subvert his officers and their Astartes to the service of the Dark Gods and to build support for his plan of rebellion against the Emperor. He took up the Emperor's old offer and renamed the XVI Legion the Sons of Horus. Horus was now allied body and soul to the Ruinous Powers of Chaos, and he had a new vision for the Imperium with himself rather than the Emperor at its head. Renouncing his oath to the Emperor, Horus led his Legion into worship of the myriad Chaos Gods. He then sought to turn many of his fellow Primarchs to Chaos, and succeeded with Angron, Fulgrim and Mortarion, who were the first of the 8 other Primarchs and Space Marine Legions that would follow Horus and his Astartes into betrayal.

The majority of the Sons of Horus, already fiercely loyal and proud of Horus, had no hesitation in following their Primarch's lead. They quickly renounced their oaths to the Emperor and supported Horus' ambitions and his new Gods of the Warp. The Chaotic corruption spread to every Imperial Adepta with which Horus had dealings, including a portion of the Adeptus Mechanicus, and from there to the Collegia Titanica and the Legio Cybernetica, eventually creating the splinter-faction of the Mechanicus called the Dark Mechanicus and unleashing the terrible civil war between Loyalist and Traitor Mechanicus factions known as the Schism of Mars. The other Primarchs Horus knew like brothers, and he was already well practiced at motivating them. Appealing to their pride, martial prowess, and courage, whilst playing upon past grudges and favours against the Emperor and the other Primarchs, the Warmaster gained the loyalty of fully half the Primarchs and their Space Marine Legions. He convinced them to first rid their Legions of any remaining Loyalists during the Battle of Istvaan III and next nearly destroyed three full Loyalist Legions during the Drop Site Massacre on Istvaan V.

The Horus Heresy
The terrible galactic civil war that followed and lasted for 7 Terran years of genocidal death and destruction on a scale never before witnessed by Mankind, called the Horus Heresy by later generations, was the most terrible conflict in the history of the Imperium, and came close to shattering it forever. Horus and his Traitor Legions moved relentlessly towards Terra, determined to throw down the Emperor once and for all. Space Marine fought Space Marine as Terra itself was finally invaded during the climax of the Heresy, and the Imperial Palace itself was besieged and breached by the Forces of Chaos during the Battle of Terra. But in the end it was Horus who was slain by the psychic power of the Emperor aboard his Battle Barge Vengeful Spirit, and with him died the rebellion. It was a traumatic and devastating blow for the Sons of Horus. Leaderless, the remnants of the XVI Legion fled into the Eye of Terror, where the Legion's First Captain Ezekyle Abaddon eventually rose to claim the mantle of Warmaster of the Forces of Chaos and become Horus' heir as the greatest of the Champions of Chaos.

The Great Cull
Having fought their way clear of the Sol System in the aftermath of the Battle of Terra, the Sons of Horus eventually fled to the Eye of Terror and established themselves upon a Daemon World that served as both a tomb for their lost Primarch and a fortress from which they would launch further attacks both upon their fellow Traitor Legions and against the still-smouldering Imperium in the form of the Black Crusades. Bereft of their glorious Primarch, the Sons of Horus Legion floundered, and in desperation sought out the favour of each of the Chaos Gods in turn in their search for renewed power, inviting daemonic possession and the ever more costly blessings of the Warp. All the while, the XVI Legion suffered the jealous attacks of their former allies amongst the Forces of Chaos as the brief unity between the Dark Gods once more broke down into the normal state of internecine rivalry. At length, one such rival Traitor Legion, the remnants of the Emperor’s Children, stole the body of the slain Horus from the heart of its tomb and spirited it away, some say with the purpose of cloning it in order to create a new and still greater Warmaster to restore the Traitor Legions' fortunes.

The salvation of the Sons of Horus came when its former First Captain Ezekyle Abaddon, now known as Abaddon the Despoiler, led a counter-attack on the Emperor’s Children that destroyed the body of Horus and in so doing ushered in a new age for the XVI Legion. The Sons of Horus changed their name once more, this time in reference to the fact that their armour was now coloured black in mourning for the death of Horus and their failure to achieve his dream of overthrowing the Emperor, calling themselves simply the Black Legion. Through his actions, Abaddon had reinvigorated the Legion, reviving the old notion that none could stand in their way and that they stood first amongst the Traitor Legions, destined by the will of Dark Gods to one day inherit the galaxy itself. When the warbands of the Black Legion gather under the wrathful banner of Abaddon the Despoiler to unleash yet another Black Crusade to overthrow the False Emperor, the words of Horus are heard upon their lips -- let the galaxy burn. The Long War for control of the galaxy by the Forces of Chaos and the Black Legion had begun.

Notable Campaigns

 * First Pacification of Luna (Unknown Date.M30) - This early Imperial campaign was the first operation mounted by elements of the early Space Marine Legions beyond the skies of Terra. The Unification Wars were still raging across the surface of Mankind's birth world. Luna was the bastion of a conglomeration of resurrectionist gene-cults whose members believed that human nature was both fractal, fractured and transcendent. Each of these Selenar gene-cults clung to a different set of archetypes. Every cult member was a product of creation by the Selenar gene-wrights according to formulae crafted in the Dark Age of Technology. Resurrected in body time and time again they sought to distill the true personification of a single human archetype. In their subterranean complexes the cults were powerful, insular and resistant to the Imperial Truth. The Imperials would have normally dealt with these insular cults in the usual matter they handled all of the other Terran factions and techno-barbarian states that refused to accept the rule of the Emperor of Mankind -- by obliteration. The fact that the Selenar gene-cults had something that the growing Imperium needed complicated that position. The Selenar returned the Imperial entreaties for alliance with silence. As the threats of the Imperium soon began to outnumber its offers, the Selenar cults began to gird themselves for war. So it was that the Emperor finally ordered Luna to be pacified by the sword, their superstitious beliefs cast down before the Imperial Truth and their gene-craft yoked to the needs of the Imperium. To this task the Emperor set the three of his newborn Space Marine Legions most suited to this purpose on what some Imperial chroniclers name as the first true battle of the Great Crusade. The combined force of the VII, XIII and XVI Legions (later named the Imperial Fists, Ultramarines and Luna Wolves) lifted from the surface of Terra in a scattering of rocket flame. The as yet unnamed XVI Legion had been chosen to serve as the Space Marine force's vanguard, and had brought its full strength to bear. Cutting power to their assault craft, the Astartes of the XVI Legion drifted silently towards Luna through the void like arrows fired into the night. As the smaller wave of assault craft belonging to the VII and XIII Legions approached the airless world, the Selenar defensive weapon systems embedded in Luna's surface lashed the oncoming Imperial force. The XVI Legion's assault craft, unlooked for and unseen, struck their targets like a dagger in the night. Within six hours of the first shot being fired, Luna had been pacified and brought into Imperial Compliance, the first off-world conquest of the Imperium of Man. Faced with annihilation, the surviving Selenar cultists bent the knee instead, their surrender communique transmitted to Terra calling for the Emperor to "call off his wolves." Broken and humbled, the enslaved gene-wrights of Luna would help forge the next generation of Space Marine who would carry out Mankind's conquest of the stars. As for the XVI Legion, they had earned their name -- the Luna Wolves.
 * The Gorro Hollowing (Unknown Date.M30) - Within the Telon Reach was an Ork empire that rivalled that centred on Ullanor, and at its heart was the scrap world of Gorro. The Ork tech-caste, the Mekboyz, dominated the Orks of Gorro and had made the world their own. The dominant tech-caste on Gorro seemed to be fascinated by a form of plasma technology never encountered before or since. Capable of generating destructive yields of terrifying potency, these plasma weapons had done much to blunt the Great Crusade's advance across the Telon Reach. The Emperor decreed that Gorro must be destroyed. When a thousand-strong fleet of warships dropped out of the Warp above Gorro it was the Emperor Himself who gave the order to begin the assault. Horus, ever the dutiful and favoured son, stood at the Emperor's side and watched as tens of thousands of assault craft spread out from the fleet. The Luna Wolves teleported into the scrap layers beneath the planet's surface, forced to hollow out Gorro from within due to the planet's high resistance to orbital bombardment. In the vanguard was the Emperor and by his side was Horus and a guard of black-armoured Justaerin Terminators from the Luna Wolves' 1st Company as well as the golden-clad warriors of the Legiones Custodes. As the Space Marines attacked, the Ork resistance they faced was near overwhelming. The Orks of Gorro were huge and augmented with scavenged bionics. Some stood taller than Dreadnoughts and their weaponry burned through Power Armour easily. At the height of the battle, the fury of the Orks split the Emperor from his guards. Alone he slew hundreds of them until a blast from an Ork plasma weapon weakened his defences and one of the Ork leaders seized him. The creature's strength was so great that it took hold of the Emperor and buckled his armour. As the creature's grasp closed to throttle the Master of Mankind, Horus stormed through the press of battle and cut the Ork's arms from its body with a single blow. Together father and son led their forces deeper into the vast sphere of scrap until they reached the centre of Gorro. The Emperor worked to collapse the self-sustaining plasma sphere that powered much of the world's scavenged Ork technology and that contained a Warp-fold envelope, so that Gorro would implode into the Warp. The Emperor proved successful, and without its power source, the scrap world collapsed in on itself. A hollow skin of rusted metal around an empty void was all that remained to mark the death of the great Ork empire of Gorro.
 * Castigation of Terentius (Unknown Date.M30) - When the forces of the Great Crusade first entered the Ordoni Cluster, they encountered the formidable warlord Vatale Gerron Terentius. Observing the forces arrayed against him, Terentius was forced to take the path of survival and surrendered to the Imperium. The Imperium had need of men like Terentius, and the Great Crusade gave him opportunities and riches such as he had never dreamed. Given a small fleet of warships and a handful of Imperial Army regiments, Terentius grew his forces by conquest. For five decades he rose in power and reputation, conquering worlds around the Halo Stars in the name of the Emperor. At the height of his powers, he had the ear of Malcador the Sigillite and the countenance of several Primarchs. When he finally turned against the Imperium, many were shocked. Terentius began to conquer already Compliant planets, his contra-Crusade conquering system after system in his own name, rather than for the sake of all Mankind. Soon he had entire fleets of warships, tens of millions of soldiers and the loyalty of a hundred human-settled worlds. Ringed by fortress worlds, this rebel human empire began to eat up Imperial worlds around the Halo Stars. The Imperium responded by sending Horus and his Luna Wolves Legion to not only break the Renegade but to demonstrate to any others who harboured similar ideas within the Imperial forces the inevitability of a betrayer's defeat. Horus elected to not only use his Legion to complete the task at hand but sent personal requests to his brother Primarchs for support which saw substantial strength from the Night Lords, Iron Hands, and the Alpha Legion joined to the might of the Luna Wolves. Soon the rebel forces were fragmented, driven by tales of culled worlds. It is said that it was at the very moment that Terentius realised he could not win that the Luna Wolves came for him. As they dropped from the Warp within weapons' range of Terentius' warships they annihilated half of his command fleet in one fell swoop. Horus himself teleported onto the bridge of Terentius' flagship along with 50 of the Luna Wolves 1st Company's elite Justaerin Terminators and slaughtered all they found there. Terentius died unrepentant, ending his life impaled upon Horus' Talon. With Terentius dead, his rebellion crumbled as the castigation continued with renewed fury. Horus, his pride slighted by Terentius' decision to betray the trust the Primarchs and the Emperor had once put in him, is said to have ordered the Night Lords to decimate every world within Terentius' rebel empire. The power of the Iron Hands and elements of the Ordo Reductor were brought to bear on every structure on Terentius' bastion worlds. Soon the rebels of his realm were slaughtered, their cities smashed to dust, and his homeworld's very air laced with toxins. Once the castigation was complete, Horus sent the gold-dipped skull of Terentius to Terra with the ironic warning carried on the lips of the messenger who bore it, "So perish all traitors."
 * Fall of Reillis (Unknown Date.M30) - During the first thirty years of the Great Crusade, at the fortified city of Reillis, a human settlement unwilling to accept Imperial Compliance, the defenders used secret tunnels to infiltrate behind the besieging Imperial army and hundreds of enemy shock troops swamped the Imperial command encampment. Unprepared and unarmoured, the Emperor and Horus fought back-to-back until a plasma blast stunned Horus and sent him staggering to the ground. The Emperor stood over the fallen Primarch and refused to give ground until reinforcements arrived to drive their attackers back. The Emperor had returned the favour of his son saving his life on the Ork world of Gorro. This incident helped to forge an unusually close bond between the Emperor and his gene-son, closer than that between any of the other Primarchs and their father.
 * Keylek Genocide (923.M30) - Early in the Great Crusade the Luna Wolves fought against the hostile alien reptilian race known as the Keylekid on the world of Keylek, ultimately wiping these reptilian xenos from the face of the galaxy. This was a long, brutal and miserable genocidal campaign that was fought long before Horus was made the Imperial Warmaster. At this time Horus was referred to simply as "The Commander" by the Astartes of his Legion.
 * Compliance of Davin (Unknown Date.M30) - The Feral World of Davin, codified as Sixty-Three Eight (63-8), was the eighth world brought into Imperial Compliance by the XVI Legion's 63rd Expeditionary Fleet some 60 standard years before the start of the Horus Heresy. The indigenous feral warriors of this world briefly attempted to resist being conquered by the Imperium, but were forced to surrender as they were overwhelmingly outmatched militarily by the Astartes. The warrior tribes were allowed to remain mostly intact as they had impressed Horus with their courage on the battlefield and their willingness to learn to adapt to Imperial culture. The military campaign was brief, and the Luna Wolves departed after the surrender of the Davinites, taking with them their concept of the warrior-lodge, which were quickly adopted throughout the Luna Wolves fleet. A detachment of the XVII Legion, the Word Bearers (then known as the Imperial Heralds), under the command of First Captain Kor Phaeron was left to shepherd the people of Davin into the light of the Imperial Truth. The Imperial governorship of the planet was give to Commander Eugen Temba of the Imperial Army, a close friend and confidante of Horus. Long after the 63rd Expeditionary Fleet departed the star system, the new Planetary Governor soon found that the inhabitants of Davin's moon refused to comply with Imperial rule. This would eventually result in Governor Temba and his Imperial garrison force being struck down by a sorcerous attack unleashed by Davinite shamans of Chaos on Davin's moon, an attack that would twist their perceptions away from their oaths of fealty to the Imperium, succumbing to the corrupting influence of the Plague God, Nurgle. Unknown to the Imperials, the entire population of Davin had long been servants of the Dark Gods of the Warp. The corruption of Temba and his Imperial Army garrison forces would ultimately necessitate the return of the Luna Wolves Legion 60 years later, and lead to the eventual corruption of Horus.
 * Compliance of Darrowmar (Unknown Date.M30) - The Luna Wolves fought alongside the Night Lords Legion in bringing the world of Darrowmar into Imperial Compliance.
 * Compliance of Tethonus (Unknown Date.M30) - The Luna Wolves fought against an unidentified xenos-adversary whose identity is not recorded in existing Imperial records while bringing the world of Tethonus into Imperial Compliance. This Compliance action was a long siege of the xenos fortress-states on Tethonus. Horus had tasked the masters of the Forge World of Diamat to create continental siege machines; vast artillery pieces that could devastate the most powerful fortifications. But the war machines took much longer for the forge masters to complete than planned. By the time they were finished, the campaign on Tehonus had been over for over a standard year and a half, and Horus had moved on to other conquests. So the weapons were put into a depot on Diamat against the day when he would come to claim them. Fifty standard years later, Horus would reveal his perfidy at Istvaan III, and would send raiding forces to claim these siege engines for later use in his attempt to overthrow the Emperor of Mankind.
 * Assault on Dahinta (Unknown Date.M30) - On the world of Dahinta, the Luna Wolves fought against a race of self-aware machines called the Overseers, who were led by the artificial intelligence known as the Archdroid. One of the Emperor's longest-standing commands was that no sentient machines could be allowed to exist, for they had nearly caused the extinction of Mankind when they had rebelled against their human overseers during the Dark Age of Technology. Despite heavy casualties amongst, the thinking machines were wiped from the face of Dahinta by the savagery of the Astartes. Only after the campaign had ended was the full truth learned: the Overseers had been created by a vanished offshoot of humanity that had settled Dahinta, perhaps during the Age of Technology. The Overseers had cared for their lost masters' crumbling cities long after they had become extinct or left their homeworld behind.
 * Pacification of Schravaan (Unknown Date.M31) - This was a joint Imperial Compliance conducted by the Luna Wolves, Iron Warriors, Imperial Fists, and the Emperor's Children Legions against the xenos Badoon on the world of Schravaan. The Iron Warriors won a great victory when they stormed the final refuge of the Badoon. They breached the defences and held while the other Legions carried the city beyond. During the following victory feast, Horus proclaimed Perturabo the greatest master of siege warfare in the Great Crusade. Fulgrim, the Primarch of the Emperor's Children then inquired to his brother Dorn whether he thought even the defences of the Imperial Palace could resist the Iron Warriors, in which Dorn replied that he regarded the defences as being proof against any assault if well-planned. Perturabo flew into a rage and unleashed unfounded accusations against his brother. After this the two rarely spoke, and neither Legion would serve again in the same campaign for the remainder of the Great Crusade.
 * Compliance of Krypt (Unknown Date.M31) - The Compliance of Krypt was a relatively short campaign conducted during the Great Crusade by both the Luna Wolves and the Death Guard Legions against the Orks upon the frozen plains of the world of Krypt. Fighting together for more than a week across the frozen surface of the planet, the Space Marine Legions turned the blue ice dark with xenos blood. The Luna Wolves’ Captain Garviel Loken and his 10th Company are known to have fought alongside Death Guard Battle-Captain Nathaniel Garro and his 7th Great Company at this time.
 * Tyrade System Compliance (Unknown Date.M31) - The Luna Wolves served alongside a detachment of the V Legion, the White Scars, during the Imperial Compliance of the Tyrade System. This action occurred seven years before the Battle of Istvaan III and the start of the Horus Heresy.
 * Ullanor Crusade (Unknown Date.M31) - The Ullanor Crusade was a vast Imperial assault on the Ork empire of the Overlord Urrlak Urruk during the Great Crusade of the early 31st Millennium. The capital world of this empire, and the site of the final assault, lay in the Ullanor System of the Ullanor Sector, which had long been under the dominion of Urrlak Urruk's Greenskin pocket empire. The Crusade included the deployment of 100,000 Space Marines, 8,000,000 Imperial Army troops, and thousands of Imperial starships and their support personnel. The Luna Wolves spearheaded the assault into the heart of Urlakk's fortress-palace. During the height of the assault, Horus and a retinue of Luna Wolves Terminators from the elite 1st Company came face to face with the massive Ork Warlord and a retinue of 40 Ork Nobs. Horus charged into the Nobs, hacking them apart with his Lightning Claws until he finally faced the Ork Overlord himself. Urlakk was simply no match for the Primarch's skill and unnatural power. First crippling his enemy, Horus hefted Urlakk`s broken body out onto the roof of the Greenskin's palace and threw it screaming from the battlements to fall far below amongst the horde of Orks still assaulting the lower levels. Seeing their leader defeated sent a panic through the Greenskin forces, which started to fall back from the Terminators. But the fleeing mobs found they had nowhere to run, as the outer walls had been breached by the attacking Luna Wolves, and the day turned into a slaughter. In the Overlord's chamber, Horus found every Ork and Terminator dead, apart from the gore-drenched First Captain of the 1st Company, Ezekyle Abaddon, who was surrounded by crushed and Ork bodies. The Ullanor Crusade marked the high point of the Great Crusade's vast effort to reunite the scattered colony worlds of humanity. The Orks of Ullanor represented the largest concentration of Orks ever defeated by the military forces of the Imperium of Man before the Third War for Armageddon began during the late 41st Millennium. Following the defeat of the Orks of Ullanor, the Emperor of Mankind returned to Terra to begin work on his vast project to open up the Eldar Webway for Mankind's use. In his place to command the vast forces of the Great Crusade he left Horus. Horus was raised to the rank of Imperial Warmaster and given command authority over all of his fellow Primarchs and every Expeditionary Fleet of the Great Crusade. But the Primarchs never came to terms with the Emperor's absence. Their hurt feelings over his seeming abandonment of the Great Crusade to pursue a secret project whose purpose he chose not to reveal to his sons laid the seeds of corruption that would ultimately blossom into the Horus Heresy. Yet the Emperor sent word from Terra that in honour of the great victory at Ullanor, the Luna Wolves should henceforth be known as the Sons of Horus, in honour of their Primarch's singular deeds, though Horus, with typical humility, chose not to rename his Legion at this time.


 * Compliance of Melchior (Unknown Date.M31) – The Imperial Compliance of Melchior was a joint campaign that was carried out by both the XVI Legion and the Blood Angels Legion. The world was the last bastion of the xenos known as the Nephilim -- hulking entities of roughly humanoid shape who were smooth like carvings of soapstone, with abstract shapes approximating arms and legs. Their dome heads emerged from their shoulders without a neck, and an array of olfactory slits and eye-spots ringed the surface of their skulls. In the light, the Nephilim looked like objects crafted of blown glass, their semi-transparent flesh glowing in the bright day. The Nephilim possessed an unhurried, careful agility like that of sea-going creatures seen through the walls of a glass tank. They moved deceptively slowly through air as if they were swimming in water, but they could move fast if they wished, darting and spinning, becoming difficult to hit. The alien giants, mocking humanity’s great dream of peace and unity, had left a trail of destruction behind them that had claimed a hundred worlds before they had come to rest upon Melchior. Sagan, the DeCora Spine, Orpheo Minoris, Beta Rigel II; each of these planets had been denuded of all human life, populations herded into empath-chapels as big as mountains and then slowly consumed. Even their name, Nephilim, the name of the fallen seraphs, was a name taken from ancient human mythology -- that of Terra, Caliban and Barac. The true horror of it was that the Nephilim used those they preyed upon to do their soldiering for them, snaring the pliant, the lonely, the sorrowful with their ideal of an attainable godhood. They plied their victims with stories of eternal existence for the faithful, of endless sorrow for the agnostic; and they were very good at it. Perhaps the xenos really believed that what they were doing was somehow taking their victims closer to a form beyond flesh, to an afterlife in an eternal heaven-state; it did not matter. With their advanced technology they implanted bits of themselves into their thralls to further their communion. They cut their own flesh and made living masks to mark their devotees. The Nephilim controlled minds, either through the transmitted power of their will or through the weak character of those they chose. They were an affront to the Emperor’s hope for the creation of the rationalist, secular galaxy outlined by the Imperial Truth. They represented not only an offence to the purity of a precious human ideal but in their insidious cuckoo-nest displacement of those who foolishly gave them fealty. For what the aliens fed upon, what the Scout Marines of the Blood Angels and Luna Wolves had seen and reported back, were the very lives of those who cherished them. The empty chapels were piled high with stacks of desiccated corpses, bodies that had been aged years in only hours as all living essence was siphoned from them. The Primarchs of the Legions were disgusted as the true understanding of the enemy they faced was revealed. The Nephilim fed on adulation. In the strategium of his flagship, the Vengeful Spirit, the Horus showed his brother Sanguinius, the Primarch of the Blood Angels, the plan that he had conceived to break the will of the Nephilim. Horus wanted the Blood Angels to march shoulder-to-shoulder with their cousins, cowing the aliens with the sight of an army of thousands of powerful Astartes rolling without pause to the gates of their last bastion. And then through those gates, over the battlements, not stopping, not pausing to parley or hesitate. "Like the ocean these things sprang from," Horus had said, "we will roll over the aliens, drag them down and drown them." The sheer bombast of the plan was its greatest strength, but Sanguinius had not been easily swayed to it. This blunt, brute-force approach was better suited to their more intemperate brother Primarchs, to Leman Russ or to Angron. Sanguinius felt that neither he nor Horus were so artless, so focused upon the target to the detriment of all else, but in the end he agreed. When the time came to enact their audacious plan, Horus and his Luna Wolves met the xenos army on the sparkling white plains of the Silver Desert. Before open hostilities began, Horus attempted to parlay with the Nephilim one final time, but the overconfident xenos refused to capitulate, casually informing the humans that they could not win. Horus informed the xenos commander that it had made a grave error, for it would be the Nephilim who would fall. The Luna Wolves would be the anvil upon which the xenos would break, and the Blood Angels would be the hammer. With lightning speed, the heavens screamed as a rain of ceramite Drop Pods tore through the outer atmosphere of Melchior and fell like flaming meteors towards the Silver Desert. Falling with them were Stormbird and Thunderhawk assault gunships that turned and wheeled through the air towards the gargantuan Nephilim encampment, carrying company upon company of the IX Legion. The speed of their assault was the key to victory; the alien invaders and their zealots had successfully been drawn out to confront the massed forces of the Luna Wolves, leaving the defences on their flanks thinned and permeable. But the xenos giants were not slow in their thinking, and the moment they understood that they had been duped, they would attempt to regroup and fortify. The Blood Angels did not allow that to happen. The Nephilim were broken and cut down, their cohesion shattered by the brutal deep strike. Caught between the brutal fury of two Space Marine Legions on Melchior’s shining sands, the Nephilim were finally put to the sword.
 * Compliance of Sixty-Three Nineteen (Unknown Date.M31) - The Imperial Compliance action of the world codified as Sixty-Three Nineteen (63-19) took place in the 203rd year of the Great Crusade. Forced off course by a Warp Storm, the Luna Wolves' 63rd Expeditionary Fleet discovered a system of 9 planets orbiting a yellow sun quite by accident. After entering the system they were contacted by a technologically-advanced human society based on the third planet. This world was ruled by a self-appointed "Emperor of Mankind" who claimed to be the predestined ruler of all the scattered remnants of humanity across the galaxy. He invited a delegation from the Imperial fleet to treat and pay fealty to him. The Warmaster sent his most favoured commander, Captain Hastur Sejanus and his Glory Squad to meet with this supposed "Emperor." Though initial negotiations appeared to proceed smoothly, they irrevocably broke down when the Astartes Captain dared to suggest that there was another, true Emperor of Mankind. Perceived as an insult, Captain Sejanus and his men were taken by surprise during a diplomatic parley and cut down. The death of Horus' favourite son and Mournival member would open an emotional chink in the Primarch's psyche that would later be exploited by First Chaplain Erebus of the Word Bearers Legion upon the Feral World of Davin during Horus' corruption by Chaos in the Temple of the Serpent Lodge. Though intensely grieved by Sejanus' death, Horus miraculously did not order an immediate retaliatory strike. Instead, he mobilised an Astartes "speartip" unit to stand by and prepare for a planetary assault. Horus then attempted to negotiate a second time by despatching Maloghurst and another contingent of Luna Wolves, but this mission also ended in disaster when Maloghurst's Stormbird was shot down and presumed lost. A great fleet of over 600 warships rose up from the planet's atmosphere to meet the 63rd Expeditionary Fleet, throwing down a challenge. The Warmaster responded in kind. The great naval battle that ensued is not recorded in detail in the existing Imperial records of this time, but eventually the Imperial fleet ultimately prevailed. The massive ground assault spearheaded by the Luna Wolves was led by First Captain Ezekyle Abaddon, as well as a half-dozen Titans which provided ground support while Assault Craft provided close-air support. The Luna Wolves were eventually able to close and penetrate the capital city's defences. The Luna Wolves fought their way inside the Imperial Palace until they came face-to-face with the supposed "Emperor." The false Emperor offered to surrender to the Imperial forces, but only to their overall acting commander, not his subordinate captains. The request was transmitted to the fleet, but Captain Garviel Loken of the 10th Company quickly realised that this was merely a ruse to draw Horus down to the Throne Room to be assassinated. 1st Company Captain Kalus Ekaddon, commander of the Catulan Reaver Squad, swiftly killed the man he believed to be the false Emperor. Then the true false Emperor revealed himself, striking with deadly force against those Luna Wolves that were present, and nearly succeeded in neutralising both Loken, Ekaddon and the other members of the Catulan Squad. He was only stopped by the timely intervention of the Luna Wolves' Primarch, as Horus teleported directly into the Throne Room and slew the false Emperor with a single, well-aimed Bolt Pistol shot to the head. The main part of the campaign was concluded with the death of the false Emperor. With the death of their leader, the main resistance on 63-19 collapsed, although there were some elements of the world's military forces that continued to wage a guerrilla war around the planet as well as three other worlds within the system. These resistance elements were eventually expunged through the efforts of the 63rd Expedition's attached Byzant Janizars Imperial Army regiment over the next few months. The last pocket of serious resistance to Imperial Compliance occurred in the Whisperhead Mountains located in the southern hemisphere. This last pocket of resistance would eventually be excised by Captain Garviel Loken's 10th Company over a period of three months. These hold-outs made their final stand within a formidable fortress carved out of the rock of one of the range's highest peaks. When the 10th Company fought their way inside the mountain fortress they discovered what appeared to be several primitive religious fanes or shrines. The Luna Wolves presumed that they were somehow connected to this region's superstitious worship of a being referred to as Samus. This being turned out to be a minor daemonic Warp-entity who had dwelled on and interacted with the inhabitants of 63-19 for many millennia. During the ensuing battle Samus possessed the body of one of the 10th Company's sergeants and was able to eliminate over a dozen Astartes and a number of Remembrancers that had accompanied the Luna Wolves before being cut down by the combined Bolter fire of Captain Loken and Sergeant Nero Vipus. The two Luna Wolves fired over 90 Bolter rounds into the possessed sergeant's body and then incinerated the remains with a Flamer. This was the first recorded incident in Imperial history of its military forces encountering the malefic powers of Chaos. The entire course of events was classified on the orders of the Warmaster, in order to hide the fact that an Astartes had turned on his fellow Battle-Brothers and that it was possible for the supposedly invincible Astartes to be corrupted by the malignant powers of Warp-entities, who were themselves a well-kept secret of the Imperium. Overall governorship of the world after it was brought into Imperial Compliance was given to General Rakris of the Byzant Janizars, while the adaptation of the cities and infrastructure of the world to Imperial standards was given over to Peeter Egon Momus. 63-19 was the first world that the newly-arrived Remembrancers of the 63rd Expedition added to their own records of the Luna Wolves' exploits.
 * Compliance of Murder (Urisarach) (Unknown Date.M31) - The Death World of Urisarach (officially codified as One-Forty-Twenty but unofficially dubbed "Murder" by the Astartes who fought there) was the twentieth world encountered by the 140th Expeditionary Fleet, a contingent of the IX Legion of Astartes, the Blood Angels, commanded by Captain Khitas Frome. Unable to translate the warnings from the orbiting satellite beacons placed in orbot of the world by the advanced human civilisation known as the Interex that warned approaching starships to stay away from Urisarach as a dangerous xenos species had been quarantined there, Captain Frome ordered his fleet's entire contingent of three companies of Space Marines to begin landing operations to investigate and bring the planet into Imperial Compliance. Due to the extreme atmospheric turbulence present on the world, all of the Blood Angels' assault craft attempting to land on the planet became scattered and were thrown far off-course, leaving the Imperial landing parties isolated from one another. The turbulent atmosphere also affected Vox (radio) communications and made it difficult for the Imperial forces to coordinate their movements. Ground teams soon started sending garbled transmissions to the fleet's vessels in orbit, reporting that the planet was inhabited by an extremely hostile intelligent arachnoid species, later dubbed the Megarachnids. The Megarachnids were an old enemy of the Interex civilisation, who had exiled the surviving members of the species to the world they called Urisarach as an act of mercy rather than committing xenocide as was standard policy for the Imperium. The Interex stripped the Megarachnids of their interstellar travel capabilities. To keep the aliens isolated on their new homeworld, the Interex constructed weather control devices that created powerful atmospheric disturbances and interfered with radio communications in the shape of large "trees" across the planet to deter vessels from landing on the Death World. As reports of horrific combat from the surface continued, the xenos were described as too numerous and formidable to defeat without reinforcements. Not long afterwards, the Blood Angels made urgent distress calls requesting immediate reinforcements and extraction. The last transmission received by the fleet of the 140th Expedition came from Captain Khitas Frome himself, who noted through clenched teeth, "This. World. Is. Murder." This name stuck, becoming the Imperium's informal appellation for Urisarach. A company of Astartes from the III Legion, the Emperor's Children, arrived in response to the Blood Angels' distress calls. They made the same mistakes during the initial assault as the Blood Angels, and their landing were scattered by the planet's powerful atmospheric disturbances. The company took heavy casualties but just as the Emperor's Children were about to be overwhelmed, a relief force of newly-arrived Luna Wolves Astartes from the Warmaster Horus' own 63rd Expeditionary Fleet began to land through the breach in the atmosphere. The Megarachnids assaulting the Emperor's Children were scattered and a full-scale Space Marine assault on the hostile xenos of Murder began in earnest. Ten companies of Luna Wolves, the remnants of the Emperor's Children's company, tens of thousands of Imperial soldiers drawn from the Imperial Army's Byzant Janizars, and several Legio Mortis Titans proceeded to level entire swathes of the grass stalk forests and destroy every one of the atmosphere-altering "trees" they encountered, which steadily eroded Murder's atmospheric barrier. The Warmaster Horus, who commanding the Imperial assault from his flagship Vengeful Spirit in orbit, was very pleased with the progress being made. Some consideration had been paid to initiating a withdrawal from Murder now that a proper landing zone was available to allow an easy extraction of the troops, when an unexpected visitor suddenly arrived. The Primarch Sanguinius had come to Murder to inspect the dead of his original Blood Angels landing force that had been wiped out early in the campaign. With tears in his eyes Sanguinius asked his brother Horus if he would join him in a campaign of vengeance against the foul xenos. The Warmaster replied: "Yes, let us murder Murder." Adding 5 companies of Blood Angels to the Imperial invasion force, Sanguinius fought alongside the Warmaster against the aliens. Thousands of Megarachnids poured out of the forests and canyons of Murder in an endless wave. Despite never retreating from the Imperial assault, the Megarachnids only continued to lose ground. By the sixth month of the campaign it seemed the Megarachnids would soon face extinction, when a fleet deployed by the Interex arrived in-system to determine who had assaulted the Megarachnids' reservation world. Finding contact with the highly-advanced humans of the Interex to be a more pressing issue that needed to be dealt with, the Warmaster ended the campaign against the xenos of Murder. The Megarachnids had been saved from extinction for a second time by their old enemy. Imperial records do not indicate the final fate of this savage species once the Horus Heresy began.
 * Interex Compliance (Unknown Date.M31) - The Interex was a highly advanced civilisation of humans that maintained a close alliance with various xenos races, including the ape-like Kinebrach. In many ways their technology was even more highly advanced then the technology employed by the Imperium at its height. Their world of Xenobia was first encountered by the 63rd Expeditionary Fleet during the Great Crusade. The Interex were devoted to fighting the menace of Chaos (referred by them as "Kaos") and were therefore highly suspicious of the Imperium's intentions, as they believed that the interlopers from Terra might be servants of the Ruinous Powers. While Horus and his Mournival were treating with the leaders of the Interex, First Chaplain Erebus of the Word Bearers, who had been accompanying the Warmaster as part of his entourage and who was already a secret follower of the Chaos Gods like most members of his XVII Legion, infiltrated the Hall of Devices on Xenobia, a museum that contained various artefacts and weapons drawn from the history of the Interex and their allied alien species. His objective was to steal the highly valuable and deadly Kinebrach blade known as the Anathame, a Chaotic artefact sacred to the Plague God Nurgle. After claiming the blade, Erebus rigged the building to explode to make good his escape. Feeling betrayed by the Imperials, who they took for agents of Chaos for stealing a known Chaotic artefact, the Interex's troops immediately attacked the bewildered forces of Horus, sparking a deadly confrontation. The Warmaster was evacuated off-planet by his Astartes as the Luna Wolves unleashed their full might upon the Interex. The Anathame would later play a pivotal role in the corruption of Horus by the Dark Gods upon Davin's moon. The Interex were later destroyed by an Imperial campaign and all of their worlds were brought into Imperial Compliance.
 * Battle of Davin's Moon (Unknown Date.M31) - Sixty Terran years after the world of Davin was brought into Imperial Compliance, Horus was influenced by the Word Bearers' First Chaplain Erebus to return to the feral planet. He informed the Primarch that the Imperial Governor of the world, Eugen Temba, had turned from the light of the Emperor, and foresworn his oaths of fealty to the Imperium. According to Erebus, Temba had found the inhabitants of Davin's moon unwilling to comply with Imperial rule, and so the Planetary Governor had led an occupying force to the moon in an attempt to bring the wild tribes of the moon into the light of the Imperial Truth. But during the parley with the tribesmen, Temba and his men were struck down by a sorcerous attack that twisted their perceptions away from their loyalty to the Imperium, and they succumbed to the temptations of power and immortality offered by Chaos and more specifically by the Plague God Nurgle, who claimed Davin's moon -- and Temba -- for his own. Horus personally led a combined assault force of Luna Wolves, an Imperial Army regiment of Byzant Janizars, and a detachment of Titans of the Legio Mortis onto the moon's surface. They soon discovered the wreck of Temba's flagship, the Glory of Terra, which was now a ruined derelict. The mass grave of rotting bodies of the Imperial Army garrison left on Davin were found in the nearby swamp, wearing the remnants of the uniforms of the 63rd Expeditionary Force. They seemed to confirm that Temba and all his men had perished, but this was not the case. The corpses of the Imperial Army troops were reanimated through the power of Nurgle as Plague Zombies that emerged from the swamps and attacked the Imperial forces en masse. The Luna Wolves and Byzant Janizars cut down the reanimated corpses. After this confrontation, the Warmaster led a speartip assault of Astartes into the derelict flagship. The bloated, mutant form of the Nurgle-corrupted Imperial Governor was discovered deep within the rotting vessel by Captain Verulam Moy of the 19th Company. Temba attempted to convert the Luna Wolves captain to Chaos, but Moy refused, and so the corrupted Planetary Governor cut him down. Horus arrived shortly thereafter to confront the Chaos-corrupted Temba, whose long-deceased body was now grossly enlarged, swollen with the corpulent putrescence of Nurgle. During their confrontation, the Warmaster discovered that Temba's corrupted form was immune to most forms of conventional injury. Horus also noted that Temba seemed to posses preternatural swiftness for a being so bloated and bulky, as well as formidable skill in swordsmanship. Horus fought like never before, his every move needed to parry and defend. Eugan Temba had never been a swordsman, so where his sudden, horrifying skill came from Horus had no idea. This was most likely due to Temba being armed with the stolen Kinebrach Anathame, the xenos Chaotic weapon that had been secretly stolen only scant weeks earlier from the Interex's Hall of Devices on Xenobia by the scheming Word Bearers First Chaplain Erebus. The Anathame was a tailored weapon, a blade of sentient metal dedicated to Nurgle that had been crafted by the Kinebrach metallurgists, using a technique now utterly forbidden by the Kinebrach's Interex allies. When such a blade was selected for use against a specific target, it became that target’s nemesis, utterly inimical to the very molecular being of the chosen target. During the vicious battle, Temba stabbed the fell blade into the Warmaster's shoulder where his Power Armour had been torn away. Though in agony, Horus managed to finally subdue his foe and mortally wound him. As the corrupting power of Nurgle fled his ravaged and decaying body, Temba was wracked with guilt over what he had done. Before dying, he attempted to warn Horus against the power of the entities that lived in the Warp. Temba prophesised that only Horus could avert a grim future of never-ending war, where the Emperor was trapped in living death and Mankind was held in bondage to a nightmarish hell of bureaucracy and superstition. The spark of life finally fled Eugen Temba and he died, his soul consumed by the Warp. The wounded Horus was found by his Astartes and taken back to his flagship in orbit of Davin. Soon the Warmaster fell ill from the effects of the Anathame and was struck down by a mysterious malady sufficiently virulent to affect even his superhumanly resilient immune system. His mysterious illness was even beyond the skills of the Legion's Apothecaries to cure, and so, in desperation, Horus was brought to the surface of Davin to be "healed" in the Temple of the Serpent Lodge. First Chaplain Erebus had convinced the Sons of Horus to bring their Primarch to the Davinite priests, in direct violation of the Imperial Truth. The secret sect on Davin was really a Chaos Cult, and using sorcery (which had been outlawed by the Emperor at Nikaea) the cultists managed to warp the mind of the Warmaster against the Emperor by playing on the seed of jealousy and resentment that he felt for his father after the Emperor had left the Great Crusade behind to return to Terra. Magnus the Red, the Primarch of the Thousand Sons Legion, used his own potent command of sorcery to intervene and unmask Erebus, revealing his manipulations, but Horus' corruption by the power of Chaos Undivided could not be stopped as he gave in to his feelings of jealousy, egotism and bitterness. The Warmaster emerged from the Temple of the Serpent Lodge fully healed, but subtly changed in both mind and body, as he was now infused with the power of Chaos. Once Horus fully recovered, he finally took up the Emperor's offer to rename the Luna Wolves after himself as the Sons of Horus. He then schemed with the Astartes of his Legion's warrior lodge, aided and abetted by Erebus, to overthrow the Emperor and purge the XVI Legion of its remaining Loyalist elements. Horus intended to unleash the greatest betrayal in human history in pursuit of his own mad ambition.
 * Destruction of the Auretian Technocracy (Unknown Date.M31) - Shortly after Horus' miraculous recovery on the Feral World of Davin, the newly renamed Sons of Horus encountered the human civilisation of the Auretian Technocracy on the world of Aureus during the Great Crusade. This human society had been founded during Mankind's early exploration of the stars during the Dark Age of Technology and had evolved along lines very similar to that of the Imperium, and more particularly to that of the Mechanicus of Mars. Horus and a contingent of Sons of Horus Astartes met with the Technocracy's leader, the Fabricator Consul, who represented the human government in its diplomatic talks with the Imperium. During their initial discussion aboard the landing bay of the Vengeful Spirit, Horus learned that the Auretian Technocracy made use of highly-coveted, lost Standard Template Construct (STC) technology. Upon learning this, the Warmaster turned his Bolt Pistol upon the Fabricator Consul and summarily executed him. He then ordered his men to annihilate the Fabricator Consul's personal guard who were known as the Brotherhood and who made use of Power Armour and weapons very similar to those of the Space Marines. Unknown to most of the Astartes within the Legion, the rot of corruption had begun to spread throughout the Legion shortly after Horus made his dark bargain with the Ruinous Powers. The official explanation for the Sons of Horus Legion's grievous actions against the Technocracy stated that the staff brought by the Fabricator Consul aboard the XVI Legion's flagship possessed a weapon which he planned to use to assassinate the Warmaster. This prompted the resulting conflict with the Auretian Technocracy which lasted for over six bloody months. The World Eaters fought alongside the Sons of Horus on the Technocracy's homeworld of Aureus, and their Primarch Angron personally lead the final Imperial assault on the Iron Citadel held by the Brotherhood of the Auretian Technocracy. When the blood-maddened warriors of the World Eaters' Assault Companies stormed a breach in the walls, the Brotherhood detonated explosive charges that buried the warriors under thousands of tonnes of rubble. Angron tore his way free and butchered the remaining warriors of the Brotherhood with his monstrous chain-glaive. Ephraim Guardia, the Senior Preceptor of the Brotherhood Chapter Command and Castellan of the Iron Citadel, died in the first seconds of Angron's attack. The campaign had been a brutal one, as the Brotherhood made use of highly advanced power armoured suits similar to those employed by Legiones Astartes, but they were eventually defeated and their technology was requisitioned by the XVI Legion. Horus would use the seized Auretian STC databases to entice a faction of the Adeptus Mechanicus to turn against the Emperor and join his rebellion. These Traitors would eventually form the core of what became the Dark Mechanicus and their treachery would unleash the terrible civil war within the Mechanicus that became known as the Schism of Mars.
 * Cleansing of Ariggata (Unknown Date.M31) - This was an Imperial Compliance action that was carried out jointly by the Luna Wolves, the Ultramarines and the World Eaters Legions against the world of Ariggata. A technologically advanced world, Ariggata had been isolated from the rest of humanity for many centuries, and when Imperial envoys arrived bearing word of the Emperor and the Imperial Truth, they were executed in a bloody gesture of independence. The military might of Ariggata was formidable, and thus the honour of its pacification fell to the Warmaster Horus and two other Space Marine Legions under his command. Most of the planet was quickly conquered, except for the massive fortress within which most of the leaders of the planet cowered. Eager to be on his way, Horus commanded Angron, the Primarch of the World Eaters, to take back the citadel and kill only the leaders. Eagerly, Angron led the assault. However, the fortress was heavily defended and the casualties were horrendous, a dozen World Eaters falling for a meter of land. Eventually, a ramp of corpses led up to a single breach in the wall, and the Astartes of the World Eaters Legion plunged in. Filled with rage over their fallen brothers, they were merciless. By the time the Ultramarines arrived, the battle was all but over. The inside of the fortress was filled with the dismembered and mangled corpses of the defenders, for not one soul had been spared the vengeful fury of the World Eaters. It was an absolute slaughter, the fortress having been transformed into an abattoir of human blood. The Ultramarines were disgusted by this savage behaviour and reported the World Eaters' growing barbarism to the Emperor. But Horus, already corrupted by the tempations of Chaos, knew that the World Eaters' savagery would make service to Khorne a good fit for the Legion -- and particularly for its rage-fueled Primarch.
 * Battle of Istvaan III (Unknown Date.M31) - The Imperial Planetary Governor of Istvaan III, Vardus Praal, had been corrupted by the Chaos God Slaanesh whose cultists had long been active on the world even before it had been conquered by the Imperium. Praal had declared his independence from the Imperium, and had begun to practice forbidden Slaaneshi sorcery, so the Council of Terra charged Horus with the retaking of that world, primarily its capital, the Choral City. This order merely furthered Horus' plan to overthrow the Emperor. Although the four Legions under his direct command -- the Sons of Horus, the World Eaters, the Death Guard and the Emperor's Children -- had already turned Traitor and pledged themselves to Chaos, there were still some Loyalist elements within each of these Legions that approximated one-third of each force; many of these warriors were Terran-born Space Marines who had been directly recruited into the Astartes Legions by the Emperor himself before being reunited with their Primarchs during the Great Crusade. Horus, under the guise of putting down the rebellion against Imperial Compliance on the world of Istvaan III, amassed his troops in the Istvaan System. Horus had a plan by which he would destroy all of the remaining Loyalist elements of the Legions under his command. After a lengthy bombardment of Istvaan III, Horus despatched all of the known Loyalist Astartes down to the planet, under the pretence of bringing it back into the Imperium. At the moment of victory and the capture of the Choral City, the planetary capital of Istvaan III, these Astartes were betrayed when a cascade of terrible Life-Eater virus-bombs fell onto the world, launched by the Warmaster's orbiting fleet. Captain Saul Tarvitz of the Emperor's Children, however, was aboard his Legion's flagship Andronius and discovered the plot to wipe out the Loyalist Astartes of the Traitor Legions. He was able, with help from Battle-Captain Nathaniel Garro of the Death Guard who was in command of the Death Guard frigate Eisenstein, to reach the surface of Istvaan III despite pursuit and warn the Loyalist Space Marines he could find of all four Legions of their impending doom. Those that heard or passed on Tarvitz's warning took shelter before the virus-bombs struck. The civilian population of Istvaan III received no such protection: 12 billion people died almost at once as the lethal flesh-dissolving virus called the Life-Eater carried by the bombs infected every living thing on the planet. The psychic shock of so many deaths at one time shrieked through the Warp, briefly obscuring even the glowing beacon of the Astronomican. The Primarch of the World Eaters, Angron, realising that the virus-bombs had not been fully effective at eliminating all the Loyalists, flew into a rage and hurled himself at the planet at the head of 50 companies of World Eaters Traitor Marines. Discarding tactics and strategy, the World Eaters Traitors worked themselves into a frenzy of mindless butchery fed by their growing allegiance to the Blood God Khorne. Horus was furious with Angron for delaying his plans, but Horus sought to turn the delay into a victory and was obliged to reinforce Angron with troops from the Sons of Horus, the Death Guard, and the Emperor's Children. Fortunately, a contingent of Loyalists led by Battle-Captain Garro escaped Istvaan III aboard the damaged Imperial frigate Eisenstein and fled to Terra to warn the Emperor that Horus had turned Traitor. On Istvaan III, the remaining Loyalists, under the command of Captains Tarvitz, Garviel Loken and Tarik Torgaddon, another Loyalist member of the Sons of Horus, fought bravely against their own traitorous brethren. Yet, despite some early successes that delayed Horus' plans for three full months while the battle on Istvaan III played out, their cause was ultimately doomed by their lack of air support and Titan firepower. During the battle the Sons of Horus Captains Ezekyle Abaddon and Horus Aximand were sent to confront their former Mournival brothers, Loken and Torgaddon. Horus Aximand beheaded Torgaddon, but Abaddon failed to kill Loken when the building they were in collapsed. Loken survived and witnessed the final orbital bombardment of Istvaan III that ended the Loyalists' desperate defence. To prove his worth and loyalty to Lord Commander Eidolon of the Emperor's Children -- and thus to his Primarch, Fulgrim -- Captain Lucius of the 13th Company of the Emperor's Children, the future Champion of Slaanesh known as Lucius the Eternal, turned against the Loyalists that he had fought beside because of his prior friendship with Saul Tarvitz. Lucius slew many of them personally, an act for which he was then accepted back into the Emperor's Children Legion on the side of the Traitors. In the end, the Loyalists retreated to their last bastion of defence, only a few hundred of their number remaining. Finally, tired of the conflict, Horus ordered his men to withdraw, and then had the remains of the Choral City bombarded into dust for a final time from orbit.
 * Drop Site Massacre of Istvaan V (Unknown Date.M31) - The world of Istvaan V was the location of the infamous Drop Site Massacre where the Traitor Legions of the Warmaster Horus redeployed following the virus-bombing of the Traitor Legions' own Loyalist members at Istvaan III at the start of the Horus Heresy. Upon learning of the terrible atrocity Horus had committed, the Emperor deployed seven Loyalist Legions of Space Marines to bring Horus to account for his actions. The Iron Hands, Salamanders and Raven Guard made up the first wave of the attack, but were pushed back by the superior tactics of Horus' maddened Chaos Space Marines. The Loyalist reserves were called in, but the four Space Marine Legions comprising them -- the Iron Warriors, the Alpha Legion, the Word Bearers and the Night Lords -- had also secretly betrayed the Emperor and were prepared to follow Horus and swear themselves to Chaos. The three Loyalist Legions were almost annihilated in the resulting crossfire but several thousand survivors from each Legion managed to escape off-world, though they were too decimated to play much of a further role in the defence of the Imperium from Horus' betrayal. The ensuing civil war pitched the whole Imperium into anarchy and chaos. It was not only the Legions aligned to Horus that rebelled, for the warrior lodges and the taint in general had spread far and wide by the time of the Drop Site Massacre. The Imperial Army was split almost in half, regiment fighting regiment and fleet fighting fleet. The Titan Legions of the Mechanicus, were equally affected, and soon fully half of the Emperor’s hosts were engaged in bitter conflict with the other. Barely a single world in the Imperium was untouched by a war that lasted for seven standard years and cost countless billions of lives before finally culminating in Horus' assault on Terra itself.
 * Destruction of Dwell (Unknown Date.M31) - Shortly after the infamous campaign on Istvaan V, the Sons of Horus were forced to recoup their losses. Another change, forced on the XVI Legion, was the loss of the Mournival. With the deaths of two of their former brothers, the Loyalists Garviel Loken and Tarik Torgaddon on Istvaan III, there were openings available to those that might be deemed worthy. Captain Horus Aximand approached First Captain Ezekyle Abaddon with the proposition to select two new members to fill the vacancies. They argued over who they thought would be worthy to join a newly reconstituted Mournival. After much debate, they both finally come to an accord, agreeing on suitable replacements. These would be Falkus Kibre, the commander of the Catulan Reaver Squad and Sergeant Grael Noctua. With rumours of the infamy of Horus' actions in the Istvaan System spreading across the nearby systems, a series of ferocious repercussive combats had flared through the Momed, Instar and Oqueth Sectors. The instigator was a leader of the Iron Hands Legion's "Iron Tenth", a warleader of the Sorrgol Clan named Shadrak Meduson. He had marshalled the Loyalists against the approaching Traitors of the 63rd Expeditionary Fleet. The Iron Hands warleader and his formations had come too late to stand with his Primarch Ferrus Manus at Istvaan V. He had gathered 58 full battalions of the Imperial Army about him -- warhosts from the Momed Voidhives, along with a flotilla of siege hulks from Nahan Instar, a half-broken cadre of Salamanders Astartes, some Mechanicus claves, and a White Scars raid-force rerouted from a return voyage to the Chondax war front. The world of Dwell, with its fortified cities, orbital batteries, ship schools, and eight million pinnacle-grade fighting men, would be the cornerstone of Meduson's defensive line. The Iron Hands warleader positioned himself at the Mausolytic Precinct which was situated on a high plateau overlooking Tyjun and the Sea of Enna. The Sons of Horus launched a planetary assault against Dwell, butchering the regular human Loyalist defenders, but were caught by surprise when they encountered the ad hoc Loyalist Astartes force that had secretly fortified the system. When the Sons of Horus assault units breached the fortifications, Horus Aximand slew Meduson's second-in-command, the Iron Hands Lieutenant Bion Henricos but "Little Horus" was then attacked by a White Scars kill-formation disguised as statues. Meduson's co-commander, Captain Hibou Khan of the White Scars, lead the Loyalist counterattack against the Traitors, but they were quickly driven off with the arrival of Sons of Horus reinforcements. One of the White Scars managed to gravely wound Aximand by slicing off his face. The XVI Legion's Apothecaries managed to reattach Aximand's severed face, but the muscle grafting left a wicked scar which made him look more brutal. It set the character of the face differently, altered the seating of the muscles so that his appearance now matched the growing corruption within his heart. Somehow, the wrongness, the imperfection, made him seem even more like Horus, not less.
 * Battle of Terra (Unknown Date.M31) - As the events of the Horus Heresy neared their tragic conclusion seven years after the fateful betrayal at Istvaan III, those Loyalist Legions not committed to the defence of Terra raced through the Warp, converging on the homeworld of Mankind. The Traitor Legions also massed above Terra to assault the Imperial Palace. The Battle of Terra was the final confrontation of the Horus Heresy that raged on Terra itself between the Forces of Chaos led by the Warmaster Horus and the Loyalist armies of the Imperium of Man led by the Emperor of Mankind himself. The Loyalist forces ultimately proved victorious in their defence of the Imperial Palace, though only just barely, and Horus was ultimately slain by the full psychic powers unleashed by the Emperor on the deck of his massive Battle Barge the Vengeful Spirit, though the Master of Mankind was mortally wounded and had to be interred within the cybernetic life support mechanisms of the advanced psychic augmentation technology known as the Golden Throne. The outcome of the Battle of Terra shaped the destiny of humanity for the next 10,000 standard years. The Traitor hosts began their fighting withdrawal, and in the anarchy and confusion Horus’ body was recovered by his Legion from his flagship. Having fought their way clear of the Sol System the XVI Legion fled for the Eye of Terror where the Sons of Horus established a world that was at once the tomb of their lost Primarch and a fortress from which they would launch further attacks both upon their fellow Traitor Legions and against the smouldering Imperium. Thus began the Long War of the Forces of Chaos to overthrow the Corpse Emperor. With Horus slain, First Captain Ezekyle Abaddon emerged as the Warmaster's heir, commanding both the Sons of Horus and what remained of the splintering Forces of Chaos. Soon known as Abaddon the Despoiler, he renames the Sons of Horus the "Black Legion" and declares himself the new Warmaster of Chaos Undivided. Highly favoured by the Chaos Gods, Abaddon intends to complete the task begun by Horus and see the Emperor slain and the Imperium ground beneath the boots of the XVI Legion.
 * 1st Black Crusade (ca.781.M31) - Abaddon the Despoiler, the self-appointed heir of Horus and the new Warmaster of Chaos Undivided after Horus' death, makes his first attempt to launch a new offensive against the Imperium of Man following the Horus Heresy when his forces initiate the First Battle of Cadia. This attempt fails and the Forces of Chaos are unable to penetrate the Cadian Gate that will allow them to take control of the only truly navigable pathway out of the Eye of Terror and into Imperial space. For the next 10,000 standard years, Abaddon will bend all of his efforts to finding a way to complete what Horus began and launch a Chaotic war that will conquer Terra and eliminate the Corpse Emperor. These massive assaults become known as "Black Crusades" to the people of the Imperium.
 * 2nd Black Crusade (597.M32) - The 2nd Black Crusade saw another failed assault by the Forces of Chaos led by Abaddon the Despoiler from the Eye of Terror against the defences of Cadia.
 * 3rd Black Crusade (909.M32) - The 3rd Black Crusade was carried out by the great Chaotic force known as The Host of Tallomin. The Host was lead by the Daemon Prince Tallomin but the assault was crushed by Imperial forces lead by the Space Wolves Space Marines. Tallomin, known as the "Prince of Daemon Princes" was either slain or banished by the Astartes who confronted him, but his final fate remains unknown to the Imperium.
 * 4th Black Crusade (ca. 001.M34) - Abaddon's forces succeed at carrying out the destruction of the Citadel of Kromarch on the world of El'Phanor before the Forces of Chaos are crushed once more by the Imperium's stalwart defenders.
 * 5th Black Crusade (723.M36) - Doombreed, an ancient Daemon Prince of Khorne whose existence precedes that of the Imperium itself, declares war on the Adeptus Astartes. The Warhawks and the Venerators Chapters of Space Marines are lost in the fighting before the Forces of Chaos are successfully turned back.
 * 6th Black Crusade (901.M36) - No information about this conflict is currently available in Imperial records. The Black Legion may have taken part in this conflict.
 * 7th Black Crusade (811.M37) - The 7th Black Crusade was a great campaign launched against the forces of the Imperium of Man led by the infamous Chaos Champion Abaddon the Despoiler and his Black Legion, which emerged out of the Eye of Terror in 811.M37. When the Blood Angels Chapter battled against the Forces of Chaos at Midian, Abaddon singled them out with implacable fury. He led a band of Khornate Berserkers into the teeth of the positions held by the Blood Angels' Devastators. Even the Blood Angels' own Assault troops could not dislodge the frenzied warband and recapture the bodies of their comrades. But there is an obscure reference to the Blood Angels being saved by an unidentified Space Marine Chapter of mysterious origin. Written within the The Canticle of Cassandria Lev - Vol. CVI, the eponymous Sainted Sisters' highly mythologised and oblique account of the wars of the 7th Black Crusade, is found mention of a "grey-clad" Space Marines Chapter who came from "The outer night" to aid the Imperium, and whose "Jagged maw did swallow the stars ... and whose ... black gaze did mirror the void of oblivion." In the course of the canticle this Chapter's ships set upon Abaddon's forces following the disastrous defeat and routing of the Blood Angels at Midian and attacked the pursuing forces as Saint Lev writes: "...fell upon the servants of the skulled-one with great fury from the darkness, unseen as the beast that lurks beneath the black waters, death for death, blood for blood...thus were the Sons of Sanguinius bought respite, and did turn back upon their pursuers and so were the damned traitors of the false gods driven unto their ruin." Images of these events can be found upon the walls of the Cemetery World of Hypasitis created to house the honoured dead of that war, depicted in repeated fresco and bar relief. Curiously, the faces of the intervening Space Marines depicted there are obscured with featureless disks of black obsidian. Given the largely unknown history of the star-faring Carcharodons Chapter, accounts of their activities can only be constructed from recorded historical incidents and fragmentary records that are believed to have involved the Carcharodons on balance of evidence. This notable engagement is listed by Imperial savants as a "[Special] Probable Encounter/Recorded Sighting" of this notorious and mysterious Space Marine Chapter.
 * 8th Black Crusade (999.M37) - No information about this conflict is currently known in Imperial records. The Black Legion may have taken part in this conflict.
 * 9th Black Crusade (537.M38) - The 9th Black Crusade was a campaign led by the infamous Chaos Champion Abaddon the Despoiler and his Black Legion that was launched out of the Eye of Terror in 537.M38. During this time, the Lamenters Chapter was recalled along with a number of other Crusading Chapters by the High Lords of Terra to help deal with the rising threat of Chaotic incursions from the Eye of Terror. But the Lamenters' fell reputation for suffering bitter reversals and dark turns of fate worked against them during the Chaos attack on the Hive World of Corillia during this campaign. The superstition-bound Mortifactors Chapter refused to fight alongside the Lamenters, abandoning the planet rather than serve beside them. Unwilling to desert the Hive World's population, the Lamenters held out alone against the Black Legion's onslaught for six standard weeks, suffering horrendous losses until the Ultramarines and White Scars led a battlegroup that broke though the Chaos warfleet to relieve Corillia. Reduced to barely 200 surviving Battle-Brothers by their sacrifice, the Lamenters were deemed lost when their fleet disappeared in a Warp Storm soon afterwards, only to reappear more than a standard century later on the edge of the Segmentum Solar, having slowly battled their way back from the outer void.
 * 11th Black Crusade (301.M39) - No information about this conflict is currently known in Imperial records. The Black Legion may have taken part in this conflict.
 * 12th Black Cruade (139.M41 - 160.M41) - Better known as the Gothic War, the 12th Black Crusade was fought for control of the Gothic Sector in the Segmentum Obscurus between the Forces of Chaos of Abaddon the Despoiler and the defenders of the Imperium.
 * Raid on Cadia (777.M41) - A sizable Black Legion warband exits the Eye of Terror in 777.M41. Cadian Imperial Guard forces slow the onslaught, but it takes a determined counter-attack from the Imperial Fists Chapter to throw the Chaos Space Marines back into the Warp rift.
 * Second Aurelian Crusade (Unknown Date. M41) - Just when all seemed to be returning to normal in the Sub-sector Aurelia of the Korianis Sector, the Warp opened up and spat out the former capital world of the Sub-sector and ancient homeworld of the Blood Ravens Chapter of Space Marines, the Ice World of Aurelia. Home to the Blood Ravens' ancient Fortress-Monastery of Selenon and many loyal citizens of the Imperium, the planet was corrupted by a Greater Daemon of Nurgle known as Ulkair. Chapter Master Moriah had attempted to destroy the daemon but failed, and the weakened daemon was imprisoned in the depths of Keep Selenon by Azariah Kyras, then a Librarian of the Blood Ravens. Yet the daemon's influence proved too strong and eventually the shaken Kyras fell to the taint of Chaos. Aurelia itself was swallowed by the Warp and its existence in the sub-sector that had been named after it was all but forgotten. Yet the ice-encased world returned to realspace in the late 41st Millennium bearing the foul hordes of Chaos, a warband of Chaos Space Marines from the Black Legion led by the Chaos Lord Araghast the Pillager and the former Word Bearers Dark Apostle Eliphas the Inheritor, who had been resurrected by the will of the Dark Gods so that he might seek the destruction of the Blood Ravens, now as a member of the Black Legion. Captain Gabriel Angelos and Commander Aramus rallied the Blood Ravens Astartes of the 3rd and 5th Company to face this threat, but no sooner did they join combat then the Eldar and the ever present Orks rose up to cause trouble along with the heretical soldiery of the Hive World of Meridian's noble House Vandis. Before long the entire Sub-sector was embroiled in fresh combat against multiple foes with the Forces of Chaos causing havoc at will. As the Blood Ravens scrambled to respond to these threats even more dire circumstances came to light as the Space Hulk Judgment of Carrion returned to the Sub-sector. Determined to recover valuable intelligence and ancient advanced technology from the Space Hulk to aid them against the foul servants of Chaos, the Blood Ravens under the command of Sergeant Aramus assaulted the Judgment of Carrion only to discover the bodies of fallen Blood Ravens from the 5th Company, formerly members of an expedition led aboard the Space Hulk by Apothecary Galan. As the forces of Sergeant Aramus investigated the Hulk they were shocked to find evidence of Galan's corruption by the powers of Chaos, but the truth of the matter was far more insidious. As Sergeant Aramus and Captain Angelos desperately fought to keep control of the Sub-sector and unlock the secrets of both the Judgment of Carrion and the lost planet Aurelia, they were interrupted by the arrival of Apollo Diomedes, the Captain of the Blood Ravens Honour Guard and the right hand of the Blood Ravens' Chapter Master and Chief Librarian Azariah Kyras. Diomedes ordered all Blood Ravens forces to stand down, an order both Angelos and Aramus promptly ignored. As Diomedes got increasingly sterner in his orders Aramus and Angelos continued to resist the forces of the Black Legion, with whom the Chapter had recently avoided open conflict for an unknown reason. Eventually Sergeant Aramus discovered the Chaotic corruption of Techmarine Martellus, formerly presumed to have died in the crash-landing of his Thunderhawk on the world of Typhon Primaris but who Sergeant Aramus had fought to recover upon discovering his continued survival. Unfortunately Martellus survived only with the corrupting help of Chaos, as the Techmarine became a lackey of the tainted Apothecary Galan and his patrons within the Chapter. As his investigations continued, Sergeant Aramus discovered to his horror that the source of corruption was none other than Chapter Master Kyras himself, who had fallen under the sway of the Greater Daemon Ulkair on Aurelia and spread his taint to Galan aboard the Space Hulk Judgment of Carrion. Kyras escaped the doomed planet Aurelia aboard the Space Hulk and had returned to the Chapter with his dark seed of corruption when he met with Galan's expedition. Daring open conflict with Captain Diomedes' forces in their base-camp on Calderis, Sergeant Aramus attacked Apothecary Galan, slaying the Traitor and his tainted bodyguard of Terminators, a battle which ended in a confrontation with Captain Diomedes himself. Reluctant to accept the corruption of his political patron within the Chapter, Diomedes found himself torn but let Sergeant Aramus and his comrades leave Calderis and continue their operations against the Black Legion warband of Araghast the Pillager. The Battle of Aurelia culminated in the death of Eliphas the Inheritor, who seized control of the warband by betraying Araghast and leaving him to the mercies of the Blood Ravens earlier in the fighting. Despite Eliphas' machinations, Sergeant Aramus was able to re-seal the Daemon Ulkair in its icy tomb within Keep Selenon on Aurelia. Even with this victory, Chapter Master Kyras declared Captain Gabriel Angelos a Renegade and Traitor to the Chapter and Sergeant Aramus found himself faced with the knowledge that the Chapter Master was a corrupt agent of the Chaos Gods. Diomedes and Aramus returned to the Chapter to bide their time while Angelos fled Kyras' wrath. When the time was right the 3rd Company was determined to return and join with Aramus and Diomedes to cleanse the Chapter of the insidious taint that lay like a malignant cancer at its core.
 * Raid on the Moons of Drathorian (998.M41) - Chaos Space Marines belonging to the Black Legion attack and pillage a space refinery used to extract Promethium from ore mined on the moons of Drathorian in the Acteron Sector. The refinery is completely destroyed in the attack. How the Black Legion came to be so far from the Eye of Terror and the purpose of the Chaos Space Marines' raid continues to be the subject of Inquisitorial investigation.
 * 13th Black Crusade (999.M41) - Abaddon the Despoiler, the Lord of the Black Legion, managed to unite all the Forces of Chaos that exist within the Eye of Terror under his leadership as the Warmaster of Chaos Undivided in 999.M41 after decades of preparation to unleash the greatest Chaotic assault upon the Imperium of Man since the Horus Heresy, more than 10,000 standard years ago. This great campaign, Abaddon's 13th Black Crusade against the realms of the Emperor of Mankind, focused its assaults upon the sectors of the Segmentum Obscurus surrounding the Fortress World of Cadia and the Cadian Gate it protected. The Cadian Gate is the only known free passage through the roiling Warp Storms of the Eye of Terror into Imperial space, and the capture of Cadia would allow the Forces of Chaos their first uninterrupted chance to assault Imperial space in millennia. In the end, after months of truly titanic fighting that spread across hundreds of worlds and tested the resources of the Imperial military as never before, the campaign wound down in a stalemate. Though Abaddon's Chaotic forces were able to gain a territorial foothold upon Cadia itself, the Imperial Navy's Battlefleets proved to be the victors in the massive space battles that were waged high above the world. The Forces of Chaos are currently trapped on Cadia and have lost air and space superiority to the Imperial forces, who daily bombard the Ruinous Powers' servants from the air. However, should Abaddon and his Chaotic allies discover a way to defeat the massive Imperial fleet in orbit over Cadia, the Forces of Chaos would have an open path to drive on the heart of the Imperium and perhaps assault Terra for the second time in the history of the Imperium. As the various Tyranid Hive Fleets are also inexorably moving towards the shining Astronomican beacon of the Emperor's mind that shines out like a light in the darkness from Terra, and the Adeptus Mechanicus reports that the Golden Throne is finally failing, it may well be that the current era of the Age of the Imperium, the Time of Ending, is well-named. In the face of the terrible threat presented by Abaddon the Despoiler and the other enemies of the Imperium, only one true hope may remain for the salvation of Mankind, drawn from the most ancient litany of the Imperial Creed: The Emperor Protects.

Pre-Heresy
First as the Luna Wolves and later as the Sons of Horus, the XVI Legion maintained much of their Legion structure as it had existed since the wars for Terra and Solar Unity, which had adhered closely to the Terran pattern laid down by the Imperial Officio Militaris before the Space Marine Legions' unification with their Primarchs. The smallest formation within the "Logos Terra Militia" and therefore within the Luna Wolves was the squad. This consisted of a group of Luna Wolves under the command of a Sergeant. Squads varied widely in both size and specialisation, with the majority of the units ranging between 10 to 20 Space Marines within the XVI Legion. Conversely, very specialised squads such as reconnaissance units or those that might have suffered heavy casualties, might only consist of a handful of Space Marines in active service.

The specialties and wargear of squads in the Luna Wolves included all of those generally found in other Legions, including those designated Destroyer and Seeker units, who were shunned by some and existed in lesser quantities. The Luna Wolves also maintained considerable resources in terms of armour and vehicles, with tithed industrial worlds they had brought into Imperial Compliance and good relations with the Adeptus Mechanicus ensuring a steady supply of munitions and materials for the XVI Legion, which spent such political coin readily. Even Horus, a generalist and a pragmatist, upon being given command of his Legion is thought to have adopted new squad formations after having seen their effectiveness in other Legions. For example, it is noticeable that until the Lactrical Onslaught the number of Storm Shield-equipped Breacher Squads was relatively low in the XVI Legion. The contributions of such units amongst the forces of the Imperial Fists cannot have escaped his notice. After the annihilation of the Lactrical, the number of such squads in the ranks of the Luna Wolves rose noticeably. Other anecdotal evidence of this adaptability and willingness to embrace new weapons of warfare can be found in Horus' vocal backing of the Tactical Dreadnought Armour project, with the result that his Legion was one of the first and most widely equipped with Terminator Armour and at the forefront of the development of tactics for its use in assaults.

The XVI Legion showed a preference for the use of Tactical Squads. Squads configured in this form within the Luna Wolves and later the Sons of Horus outnumbered all other squad types combined throughout the Great Crusade. Horus remarked on several occasions that there were few challenges of war that could not be met by, or did not require, the use of such units. The presence of Tactical Squads designed to be held in reserve and unleashed once a weakness in an enemy line had been identified, trained in fire saturation and carrying additional close combat weaponry for use in overrunning enemy positions -- the so-called Despoiler Squads -- shows again the dominance of the place of the Tactical Squad in Horus' tactical thinking. Such was the effectiveness of this tactic that its use was copied by several different Legions, such as the White Scars and Iron Warriors, who field Despoiler Squads of their own.

The heart of the Sons of Horus Legion was the company, which served as the Legion's principal military division. Made up of a grouping of squads under the leadership of an officer with the rank of Captain, the company was the base currency of campaigns and battles. There was no fixed strength for a company within the Luna Wolves and the Sons of Horus. While other Legions codified and enforced strict limits on the size of similar formations, this was not the case amongst the Sons of Horus, which had begun in more regimented form, but had become increasingly ad hoc in structure and disposition over time. Company strengths as small as 36 and as large 972 Astartes were recorded by datafactors during the XVI Legion's action against the Dasim Patrimony, for example.

The configuration of squad types within a company varied as widely as its strength. Some were comprised almost exclusively of Tactical Squads with a few Support Squads. Others were an eclectic mix based on the varied requirements of different campaigns and the will of Horus. By way of example, the 17th Company, known as the Hesperus Guard, had a standard strength of 205 Space Marines at the time of the virus-bombing of Istvaan III. Tactical Squads made up half this strength numerically, with the Legion placing in general great importance on the use of Tactical Squads in every deployment. The rest consisted of two veteran units, three reconnaissance units, a heavy support squad and multiple batteries of support weaponry. The elite 1st Company showed even greater variation. Small in number, it contained two distinct sub-formations: the Justaerin Terminator Squads and the Catulan Reaver Assault Squads. Both sported the black armour worn only by this elite company and each was led by a Captain under the overall command of the Legion's First Captain, Ezekyle Abaddon. Used in combination, the 1st Company exemplified Horus' predilection for precise and overwhelming attacks against strategic targets.

In other Space Marine Legions a company would form part of further layers of hierarchical military organisation, variously referred to as battalions, cohorts, chapters, regiments or by any number of other titles. Horus seems to have preferred to avoid this extra layer of fixed organisation, which eroded over time in the Legion and was largely academic by the time of their transition to become the Sons of Horus. Instead of a formal structure, Horus would group companies and individual units together as required for the execution of a particular campaign. The commander of such a formation would usually be a senior Captain. If the formation was especially large, then other Captains would take on the role of lieutenants to the overall force commander until the completion of the campaign. These formations rarely had formal titles, but the Sons of Horus commonly referred to formations intended to prosecute a rapid assault as "Speartips." In eschewing formality and fixed structure above the basic level of the company, Horus demonstrated his pragmatism and his preference for waging war with careful precision. Within the Luna Wolves and the Sons of Horus, squads also commonly had their own honorific or epithetic titles rather than simple numerations: the Illuminators Prime, Death Makers, Jerrok's Reavers, the First Sons, and similar appelations, while some were named for the Sergeant or Chieftain that led them if their leader's own reputation was strong enough alone. Many of these titles betrayed the culture of Cthonian gang honours and the tradition of reputation and internecine warfare from which they had sprung. This culture had grown steadily stronger over the years within the rank and file of the XVI Legion's intake of Neophytes.

The exact disposition of the Sons of Horus at the time of the Istvaan III Atrocity is uncertain. Given the accounts of the battle on Istvaan III following Horus' treacherous bombardment from those that survived it, it would seem likely that the culled Loyalist elements of the XVI Legion represented something approaching a third of the Sons of Horus' entire force. Records, tainted as they may be, place the Sons of Horus at a fighting strength of approximately 130,000-170,000 Space Marines in the period leading up to the Istvaan III Atrocity. Although the figure may have been higher, this estimate would also tally with more general assessments of the Sons of Horus Legion being in the upper quarter of the Legions in terms of the Space Marine manpower available to them.

The XVI Legion's Great Crusade fleet was likewise accorded to be among the greatest under any single commander's flag, with in excess of one hundred capital ships and perhaps three times that figure in smaller Cruisers and Escorts under Horus' direct command. Taking into account likely losses from the ground war that followed the virus-bombing of Istvaan III, and elements of the Sons of Horus Legion not in the Istvaan System at the time, it would follow that Horus began his war of betrayal with around 70,000-110,000 Space Marines of his own Legion at his disposal, with considerable evidence present in Imperial records that the latter figure is the more accurate.

Legion Command Hierarchy
As with all of the Space Marine Legions, Horus' command as Primarch over his own Legion was absolute. Beneath Horus were his Captains, beneath them were the squad Sergeants, and where a formation of squads came together for a purpose, the informal rank of "Chieftan" was given to the Sergeant granted field command authority, a matter not always of seniority, but rather selection of the best or most suited Astartes for the task at hand; an approach which fitted well within the Legion's pragmatic and sometimes impulsive approach to warfare. Beneath these non-commissioned officers were the rank-and-file Battle-Brothers of the Luna Wolves and the Sons of Horus. This simple hierarchy belied the truth of matters when applied in practice within the XVI Legion. Within each rank, prestige and personal reputation counted for much within the brotherhood of Space Marines. There were distinctions between those who fought with the Legion for longer, between those who had fought in different campaigns, between those who had received certain honours, and between ordinary squads and those who formed a Captain's Honour Guard. Beneath the surface of this simmered other divisions, not easily visible to the outsider, divisions of blood and origin, divisions that the mere act of becoming a Space Marine should have washed away, but for the Sons of Horus did not in many cases. These hidden divisions would eventually bear bitter fruit.

The rank of Captain within the Legion also held subtle variations of authority. Generally those in command of a lower numbered company outranked those in a higher numbered company, while those who had once had overall command of a campaign were considered superior to those officers he had commanded during that action. At the top of this informal but very real hierarchy of Legion officers were those Captains who served as Horus' closest advisors and in particular the First Captain of the Legion who commanded the elite 1st Company and also served as his Primarch's principal field officer and second-in-command. The seniormost Captains comprised the Legion's Mournival, the quartet of Astartes who served as Horus' closest advisers and companions within the XVI Legion and who existed outside the regular command structure. Before the outbreak of the Horus Heresy, the final Mournival of the Sons of Horus included Captains Garviel Loken, Horus Aximand, Tarik Torgaddon and Ezekyle Abaddon. The Mournival served as an advisory body to Horus in both military and political matters, but in truth its members held no formal power above that of the other company Captains.

Held together by Horus' personal charisma and brilliance as a leader, the command structure of the Luna Wolves and then the Sons of Horus proved highly effective, adaptable and resilient. Combined with the XVI Legion's skill in rapidly concluding campaigns, it allowed the Legion to flow from one victory to another, forming and reforming to meet each new challenge. Each Son of Horus knew his capabilities and the capabilities of those around him, both by given rank and personal repute, capabilities that were enshrined in a hierarchy determined by deeds rather than the demands of formality. Effective as it was, one cannot help but notice the importance of personal prestige and the pack-like sorting of authority as a hallmark of the XVI Legion, and upon occasion the source of some conflict and vendetta within the ranks, a seed of the terrible division to come. As the character of the Legion was an echo of its Primarch, so one can perhaps see the flaw of the father in the pride of his sons. So it was that when Horus fell from grace, so too did his sons, and their faults, long-sleeping, multiplied and grew to consume them: pride, ambition, the desire to be greater than any other and the savagery and merciless will to make such dark dreams manifest.

Specialist Ranks and Formations

 * The Mournival - The Mournival were Horus' most trusted advisors and confidants. Consisting of four chosen Captains of the Legion, the Mournival existed outside the rest of the XVI Legion's regular command structure. Together the Mournival functioned as the soul of the Luna Wolves, and later the Sons of Horus, supporting their Primarch and steering the Legion's temperament and decisions. The Mournival had many important responsibilities, which included making sure that the Legion and its Primarch lived up to their standards of moral excellence and the Emperor's vision of the Imperial Truth in prosecuting its duties and helping the Primarch devise strategies for more effectively carrying forth the Great Crusade. The Mournival on occasion even provided Horus the means to posture politically as a means to save face or present a certain united front when in the presence of the XVI Legion's Imperial allies and enemies alike. Horus relied on the Mournival to balance his decisions with questions and different perspectives. In this way the four Captains served as a combination of counsellors, confidants and naysmiths. It is known that there was an element of ritual to the bond between the Mournival brothers: meetings of the Mournival took place in moonlight, a different phase of the moon was graven on the helm of each brother, and its oaths of brotherhood were made over the reflected image of a moon. The origins of the Mournival are unclear, although there are parallels with the rites of brotherhood amongst the Jutigran clans of Terra and the ritual practice of the Selenar gene-cults of Luna, who were integral to the early integration of many Cthonian Neophytes into the XVI Legion. Whatever the Mournival's origins, its existence within the Legion certainly lies in in the early decades of the Luna Wolves' history, and it is known to have persisted for a time even after the Istvaan III Atrocity, though by then it had lost any meaningful check upon the actions of Horus and continued to exist solely due to tradition. The last members of the Mournival before the XVI Legion fell to Chaos included Captain Horus "Little Horus" Aximand (Half Moon), First Captain Ezekyle Abaddon (Full Moon), Captain Garviel Loken (New Moon) and Captain Tarik Torgaddon (Gibbous Moon).
 * Justaerin Terminator Squads - The Justaerin Terminator Squads were one of two distinct sub-formations found within the XVI Legion's elite 1st Company. Led by the Legion's First Captain, the black-armoured Justaerin were the pride of the XVI Legion. Tasked with forming the "point of the spear" of the Legion, they went where the fighting was thickest, their attack directed usually at destroying the heart of an opposing target or conducting the decapitation strike of an enemy force. Early proponents of the use of Tactical Dreadnought Armour, many of the Justaerin entered combat as Terminators, relying on the resilience this gave them to smash aside any resistance and close in for the kill.
 * Catulan Reavers Assault Squads - The Catulan Reavers Assault Squads were the other sub-formation present in the XVI Legion's elite 1st Company. They too, sported the signature black armour which denoted their specialisation in harrowing actions and hit-and-run tactics. They were led by a Captain under the overall command of the Legion and the 1st Company's commanding First Captain. They also made extensive use of Terminator Armour, taking advantage of its additional protection and ability to smash aside any opposition. Used in combination, these two elite sub-formations of the 1st Company exemplified Horus' predilection for precise and overwhelming attacks against strategic targets.
 * Despoiler Squads - The Tactical Squads known as Despoiler Squads were designed to be held in reserve and unleashed once a weakness in an enemy line had been identified. Trained in fire saturation techniques and carrying additional close combat weaponry for use in overrunning enemy positions, the so-called Despoiler Squads showed the dominance of the Tactical Squad in Horus' tactical thinking. Such was the effectiveness of this tactic that its use was copied in several different Legions.
 * Destroyer Squads - Considered dishonourable by some Legions who made little use of them or eschewed them altogether, Destroyers were equipped with and expert in the use of otherwise proscribed and forbidden weaponry. Alongside certain factions of the Adeptus Mechanicus, only Destroyer cadres had the license to use these weapons in the forces of the Imperium by the Emperor's command. Rad-weapons, bio-alchem munitions and the burning horror of Phospex were amongst the forbidden weapons in a Destroyer Squad's dark arsenal, weapons which irrevocably tainted the ground upon which they were used. Marked by their fire-blackened and chem-scalded armour, Destroyers were often shunned and deemed somehow tainted by their fellow Battle-Brothers in many Legions and were considered at best a necessary evil, although the effectiveness of their relic-weapons in cracking especially difficult enemy defences could not be denied.
 * Seeker Squads - Seeker Squads were comprised of a specialised force of Space Marines whose principal task on the battlefield was to identify an enemy's command structure, its warlords, officers, priests, demagogues, whatever form they took, and slay them with a well-placed bolt round while the battle raged round them. The Alpha Legion are said to have first crystallised the use of this tactic and squad configuration, which had with the Emperor's approval spread to the other Legions, although its use sat poorly within the combat doctrine and martial culture of some like the Space Wolves. Equipped with special issue ammunition to assist their efforts, Seeker Squads were primarily composed of the finest shots within the Legion, as a Seeker strike force often only had a small window of opportunity to take down its targets at close range, rather than enjoying the luxury of distance.

Post-Heresy
After the death of Horus at the Battle of Terra, proper hierarchical structure within the XVI Legion's squads and companies disintegrated, as was common in most of the Traitor Legions as the more deleterious effects of Chaos manifested themselves with the end of the unity between the Forces of Chaos. Those Sons of Horus who survived the Heresy formed into warbands of Chaos Space Marines of varying size and composition, led by individuals known as Chaos Champions. These Champions were either ranking officers of the Sons of Horus during the time of the Heresy, or newly emerged leaders who had won great favour with the Ruinous Powers through their violent and blasphemous deeds. When circumstances dictated, several warbands would rally together under the banner of a greater Chaos Champion, or even Abaddon himself as the Warmaster of Chaos Undivided, usually in preparation for a major raid or incursion into the Imperium. The entirety of what remains of the Black Legion only gathers when Abaddon has managed to successfully unleash a new Black Crusade.

The overriding belief of the XVI Legion's Astartes prior to the Warmaster's demise was in the ultimate superiority of Horus over all other beings in the Imperium and, by association, themselves as his genetic progeny. In continually seeking to prove themselves as the greatest of the Space Marine Legions, they did indeed achieve the most in terms of the sheer numbers of worlds brought into the Imperial fold during the Great Crusade, although much effort had to be expended by other Imperial forces to completely pacify these new worlds after the XVI Legion had moved on to the next target. The Sons of Horus' defeat and exile dealt a crushing blow to the collective ego of the Legion. This has fuelled the current Black Legion's almost fanatical intensity to restore unity amongst the Forces of Chaos in the Long War and drive on Terra to eliminate the Corpse Emperor and regain their place of primacy -- no matter the cost.

Legion Combat Doctrine
The XVI Legion was a flexible fighting force, able to adapt to almost any combat situation. The Legion possessed an efficient chain of command, which fell into disarray after its Primarch, Horus, was killed during the Battle of Terra. In the years immediately following the end of the Horus Heresy, the Sons of Horus' discipline broke down completely, as the Legion dissolved into a number of competing warbands of Chaos Space Marines, each led by a different Chaos Champion who maintained his rule through the favour of the Dark Gods and often lethal discipline. First Captain Ezekyle Abaddon ultimately managed to restore a measure of discipline to the XVI Legion and bring its disparate warbands under his control after he assumed Horus' place as the Warmaster of Chaos Undivided, mainly through exercising a level of fear and violence that could cow even the greatest of the Legion's Chaos Champions. At present, the Black Legion shows more unity of purpose and structural integrity than many of the other Traitor Legions, though only the Word Bearers Legion has managed to maintain its complete Imperial military hierarchy intact amongst the Forces of Chaos.

The Black Legion generally favours close combat over ranged firefights, and Horus' tactic of "ripping the throat out of the enemy," the annihilation of the enemy's command apparatus through the use of a small force referred to as the "speartip," is still a favoured method of attack. Black Legion commanders seek to apply constant pressure on the enemy in a number of lightning fast strikes. These sharp but limited assaults are meant to disrupt the enemy and secure positions that can be used for fire support. This in turn keeps the pressure on while new attacks are being prepared. The time-lapse between each assault decreases with each advance, and the Black Legion commander will usually wait until the pressure reaches its highest point. When this occurs, the commander will lead the best Astartes amongst his warband, usually Aspiring Champions, in a final, devastating assault; an attack in which teleport-capable Terminators often feature. Hordes of daemons summoned from the Empyrean by the Black Legion's Chaos Sorcerers are also used for frontal assaults, and to pin the enemy in place while the Legion whittles them down.

Legion Homeworld
The XVI Legion's homeworld, the ancient Mining World of Cthonia, no longer exists, having apparently lost geo-structural integrity and broken apart into asteroids and debris during the centuries following the Horus Heresy. Certainly the once ore-rich planet was riddled with mine workings right through to its dead core as the numerous gangers that formed the majority of the world's population may originally have been imported as work teams to maintain the crumbling tunnels. However there is some conjecture amongst Imperial savants that Cthonia was destroyed deliberately by the Imperium following the end of the Horus Heresy, when the Loyalist Astartes Legions moved to purge the homeworlds of each of the Traitor Legions during the Great Scouring to remove their Chaos corruption. Since the destruction of their fortress in the Eye of Terror by an alliance of Chaos Space Marines seeking to capture the body of the Warmaster Horus at the insistence of the former Emperor's Children Apothecary Fabius Bile, the Black Legion is no longer based on any particular planet, and is instead stationed permanently on various spacecraft within their large Legion fleet within the Eye of Terror. The Black Legion possesses a single ancient Battle Barge from their original fleet, as well as other vessels commandeered or captured from the Imperium over the millennia. In particular, many of the oldest Imperial Army starships that rebelled against the Imperium during the Horus Heresy now seem to be under Abaddon's command, along with newer vessels he has ordered constructed within the Eye of Terror over the last 10 millennia.

Legion Beliefs
The overriding belief that animated the Astartes of the XVI Legion prior to Horus' demise was in the ultimate superiority of Horus and themselves over all other beings in the galaxy. In continually seeking to prove themselves as the greatest of the Space Marine Legions, they did indeed achieve moe than their fellow Astartes in terms of the sheer numbers of worlds brought into the Imperial fold prior to the Heresy. The Sons of Horus' defeat at the Battle of Terra and exile to the Eye of Terror was a crushing blow to the collective ego of the Legion. It took all the strength of character of their new commander, Abaddon the Despoiler, to restore the Legion's sense of pride and refocus its Astartes on their ultimate goal -- to destroy everything that the Emperor of Mankind created and raise themselves up as the new rulers of the galaxy in the names of the Ruinous Powers of Chaos.

Legion Gene-Seed
The Black Legion's gene-seed, prior to the incident on the Feral World of Davin where Horus was brought back from the brink of death through the power of the the Serpent Temple's Chaos Sorcerers and the corruptive touch of the Ruinous Powers, was perfectly pure and unusually potent, since it was derived from Horus' genome, who was generally considered the greatest of the Primarchs. However, following their corruption by Chaos, the Black Legion's Space Marines started to exhibit random genetic mutations, and it is likely that this taint now affects their gene-seed as it has almost all of the Traitor Legions. The regular practice among the Legion's Astartes of seeking daemonic possession may also have accelerated the effect. However, such mutations are seen as a mark of favour from the Chaos Gods and are generally displayed with pride by Black Legion Astartes, though it also means that the Legion can no longer produce new Astartes from its own gene-seed to replenish its ranks since the Astartes organs will not properly cultivate or will be so genetically warped as to kill any human male they are implanted within. This inability to replace losses is a problem that afflicts all of the Traitor Legions and drives them to seek out uncorrupted Imperial Space Marine gene-seed stores whenever possible.

Notable Legion Members

 * Horus - Horus, also known as Horus Lupercal, was the Primarch of the XVI Legion and served as the first Imperial Warmaster during the Great Crusade. Once the most favoured son of the Emperor of Mankind, he ultimately became the greatest Arch-Traitor in the history of Mankind when he turned from the Emperor's light and led half the Legiones Astartes in a galaxy-wide rebellion known as the Horus Heresy. Ultimately, this rebellion failed when the Emperor confronted Horus at the climactic Battle of Terra aboard his flagship Vengeful Spirit in mortal combat and killed him, which left the Emperor gravely wounded. This would result in his ten millennia internment within the life-sustaining prosthetic device known as the Golden Throne.
 * Ezekyle Abaddon - Abaddon was the First Captain of the XVI Legion's elite 1st Company, known as the Justaerin, and was recognised as the greatest warrior of that Legion after its Primarch Horus himself. He was also the leader of the Legion's unofficial advisory council composed of four senior Captains, called the Mournival. Rumours indicate that Abaddon may have been the result of early experiments to clone Horus. Abaddon eventually became the heir of Horus as the leader of the Black Legion after Horus' death at the end of the Horus Heresy and rose to become the new Warmaster of Chaos Undivided. Abaddon, often called Abaddon the Despoiler in the Imperium, is now one of the most powerful Chaos Lords, if not the most powerful, in the galaxy. He alone possesses the power to unite all the warbands of the Black Legion as well as the other Traitor Legions into a powerful army of Chaos in preparation for one last Black Crusade against the Imperium, to finally end the Long War that began ten millennia ago.
 * Maloghurst, "The Twisted" - Maloghurst served as Horus' Equerry, public voice and political enforcer, and during the Horus Heresy he became the Warmaster's unofficial secret police chief. Maloghurst was known as 'The Twisted' for being a shrewd manipulator and the way in which his brilliant mind schemed up complex machinations. Known as a formidable warrior within the Legion there was some speculation that Maloghurst was a serious contender for the First Captaincy of the Luna Wolves which was held by Ezekyle Abaddon before the Warmaster made him his Equerry. During the campaign to bring the world designated as 63-19 into Imperial Compliance in the last days of the Great Crusade, Maloghurst was despatched by the Warmaster to the planet's surface to parlay with the false leader of this world who ironically called himself the "Emperor of Mankind." Unfortunately, Maloghurst met his fate when his Stormbird was shot down and he was horribly wounded after crash-landing on the planet's surface. His body was mangled and his spine horribly twisted. His body was now as physically twisted as his mind, which had long been given to deception and manipulation in a way that was unusual for the usually straight-forward Astartes. Though physically unable to remain on active combat duty as an Astartes, when selected by his Primarch to serve as his closest aide, Maloghurst proved more than willing. After Horus' corruption by Chaos on Davin, he conspired to overthrow the Emperor and install himself as the new ruler of the Imperium. It became Maloghurst's duty to ensure that the Warmaster's orders were carried out, in his new capacity as the chief enforcer of Horus' will. During the initial phases of Horus' plan to conquer the Imperium, he first needed to rid the various Traitor Legions of their remaining Loyalist Astartes on Istvaan III. Once he learned of the plan to exterminate the Loyalists while they were fighting in the Choral City on the planet below, the Loyalist Death Guard Captain Nathaniel Garro seized the Frigate Eisenstein in orbit of Istvaan III in order to flee to Terra and warn the Emperor of the Warmaster's treachery. It was Maloghurst who directed the Death Guard's First Captain Calas Typhon aboard his warship, the Terminus Est, to intercept and prevent the Eisenstein from escaping. Typhon failed at this task, and the Eisenstein escaped, badly damaged, into the Warp. Over the seven years of the Horus Heresy that followed, Maloghurst would become a dark, feared figure amongst his fellow Astartes and mortals alike, and would be responsible for ordering some of the most heinous crimes carried out by the Traitor Legions against civilian populations during the course of the great galactic civil war.
 * Falkus Kibre, "Widowmaker" - Falkus Kibre, known as the "Widomaker," was a Captain of the elite 1st Company who led the black-armoured Terminator Squad known as the "Widowmakers" of the elite Justaerin, Horus' personal honour guard. Following the Warmaster's fall to Chaos and turn from the light of the Emperor, Kibre willingly followed his Primarch into damnation during the Horus Heresy. He led the Justaerin during some of the most infamous campaigns during this period of upheaval and rebellion, including the Drop Site Massacre on Istvaan V and the Battle of Terra. Following the dissolution of the Mournival with the losses of Captains Loken and Torgaddon on Istvaan III during the conflict between the Traitors and Loyalists within the Sons of Horus, Horus Aximand suggested the reformation of the Mournival, proposing to First Captain Abaddon that Kibre be one of its members. Kibre was eventually recommended to become a member of the Mournival by First Captain Ezekyle Abaddon following the Battle of the Mausolytic Precinct on the planet Dwell to replace the Mournival members who had been lost. Ten millennia later, Kibre still serves Abaddon, the new Warmaster of Chaos, as part of the Black Legion's Terminator elite.
 * Kalus Ekaddon - Captain of the Catulan Reavers Squad of the elite 1st Company.
 * Tarik Torgaddon (Deceased) - Tarik Torgaddon was the Captain of the 2nd Company and a member of the Mournival who remained loyal to the Emperor when the Sons of Horus turned to Chaos. Torgaddon was killed during the Battle of Istvaan III when he was beheaded by his fellow Mournival member Horus Aximand. His headless body was often used as an imaginary interlocutor in the mad ravings of Garviel Loken, the only survivor of the battle on Istvaan III who would later be recovered by the former Death Guard Battle-Captain Nathaniel Garro to serve in the secret organisation that would become the Imperial Inquisition.
 * Iacton Qruze, "The Half-Heard" - Qruze was the Captain of the 3rd Company, a very old Space Marine who was a native of Cthonia. By the time of the Horus Heresy he was one of the only Cthonian Astartes still serving in the XVI Legion who remembered what it was like when the Luna Wolves had served only the Emperor before Horus had been rediscovered by his father. Qruze had been a captain of the Luna Wolves since the Legion's inception and was even a veteran of the Unification Wars on Terra. Considered ancient by dint of his length of service to the Legion as well as his continued die-hard loyalty to habits of the Legion from the time of its Terran past that he could not seem to break. Qruze, like most Terran Astartes in the Traitor Legions, remained loyal to the Emperor when his Horus turned to the service of Chaos in pursuit of his own ambitions. Recognising that the Sons of Horus no longer represented the Astartes he had once known, Qruze rescued the civilian Remembrancers Mersadie Oliton and Euphrati Keeler as well as the Senior Iterator Kyril Sindermann from Horus' massacre of civilians on his flagship the Vengeful Spirit and fled with them to the Frigate Eisenstein during the virus-bombing of Istvaan III. During the flight of the Eisenstein to Terra, Qruze formed a firm bond with the former Death Guard Battle-Captain Nathaniel Garro, the pair were told by Malcador the Sigillite, the Regent of Terra, that they, along with the Sister of Silence Amendera Kendel, were to form the beginnings of an organisation that would utilise "men and women of an inquisitive nature, hunters who might seek the witch, the traitor, the mutant, the xenos" -- later known as the Imperial Inquisition.
 * Hastur Sejanus (Deceased) - Sejanus had been the Captain of the 4th Company and a member of the Mournival during the Great Crusade. Sejanus was sent as an ambassador of the Luna Wolves to greet the leader of the world of 63-19 who styled himself the "Emperor of Mankind" and whose planet had not yet been brought into Imperial Compliance, and was brutally murdered. Horus had loved Sejanus like a son and felt towards him the way he believed that his own father, the Emperor, loved him. Garviel Loken replaced Sejanus on the Mourbival following the Imperial Compliance of the world designated 63-19.
 * Horus "Little Horus" Aximand - Horus Aximand, known as "Little Horus" because of his uncanny resemblance to his Primarch, was the Captain of the 5th Company and also a member of the Mournival. Aximand was originally very loyal to the Emperor and the Imperium's ideals, but reluctantly turned to the service of the Ruinous Powers when the Warmaster took ill on the Feral World of Davin and his Astartes desperately agreed to let him be cured by the Chaos Cult known as the Temple of the Serpent Lodge in direct violation of the Imperial Truth. Aximand's loyalty to Horus ran so deep that, in the end, it overrode his own better judgment and fealty to the Emperor. Aximand beheaded Tarik Torgaddon during the fighting against the Traitor Legions' Loyalists on Istvaan III, but was later overcome with regret for his actions. Both Horus and First Captain Abaddon took notice of this unexpected weakness in their comrade, but took no actions against Aximand as long as he presented no hindrance to their plans.
 * Yade Durso - Yade Durso served as the second Captain to command the 5th Company of the Sons of Horus.
 * Serghar Targost - Captain of the 7th Company and the Lodge Master of the Sons of Horus' warrior lodge, the heart of the Legion's growing allegiance to the Chaos Gods.
 * Garviel Loken - Loken was the Captain of the 10th Company and was made a member of the Mournival after the death of Hastur Sejanus. Loken possessed one of the most analytical and perceptive minds amongst the Astartes of the XVI Legion. Loken remained firmly loyal to the Emperor and his vision of a new Golden Age for Mankind and was one of the first amongst the Sons of Horus to realize that the Warmaster had changed after his miraculous healing in the Temple of the Serpent Lodge on Davin and that he was subsequently leading the XVI Legion down a dark and dangerous path. Loken, along with his friends Captain Tarik Torgaddon and Sergeant Nero Vipus, were selected by Horus to lead the Sons of Horus' participation in the campaign on the world of Istvaan III, which had recently rebelled against the Emperor and declared itself an independent principality. However, shortly after the liberation of the planet's capital, Choral City, from the Slaaneshi rebels, Horus betrayed the Loyalist Astartes he had deliberately sent to the planet below, and bombarded its surface from orbit with Life-Eater virus bombs. However, because of the heroic actions of Captain Saul Tarvitz of the Emperor's Children, many of the Loyalists manage to survive the initial bombardment. Captains Loken, Torgaddon, and Tarvitz take command of the Loyalist elements that remained and fought a three-month-long holding campaign against the Traitors that delayed their palns to move on Terra. Finally, when Horus had had enough, he sent Loken and Torgaddon's traitorous former Mournival brothers, Ezekyle Abaddon and Horus Aximand, to the planet's surface to kill Loken and Torgaddon while he prepared to wipe out the remaining Loyalists with an orbital bombardment. In the ensuing fight, Torgaddon was beheaded by Aximand, but before Loken could be similarly slain by Abaddon, the ruins they had been fighting in were crushed by the Imperator-class Titan Dies Irae. Loken somehow managed to survive the collapse fo the ruins upon him but was left badly wounded in both body and spirit, having been driven partially insane by his Legion's betrayal. He was presumed killed by the XVI Legion following the final bombardment of the Choral City, but survived and took to wandering the ruins of the Choral City, slaying the groups of wandering Plague Zombies who were raised from the corpses scattered across the dead world by the taint of Nurgle whose influence had grown on the world as a result of the use of the Life-Eater virus to kill its population. Several years later, Loken was found alive and partially insane in the ruins of the Choral City on Istvaan III by the former Death Guard Battle-Captain Nathaniel Garro, who has been sent to find Loken so that he can become one of the first Astartes to join what will become the Imperial Inquisition. Garro engaged Loken in a duel and managed to restore his sanity by reminding him of who he was and that he possessed a duty to fight the Emperor's enemies for so long as he still drew breath.
 * Nero Vipus - Locasta Tactical Squad Sergeant assigned to the 10th Company who fought on Istvaan III and remained loyal to the Emperor.
 * Xavyer Jubal - Xayver Jubal was the sergeant of the Hellbore Tactical Squad of the Luna Wolves' 10th Company. He was angered when Captain Garviel Loken chose to promote Nero Vipus to the position of senior sergeant of the 10th Company, after Garviel had been accepted into the Mournival. Jubal felt that the promotion should have gone to him, since he was of a higher rank and had served longer as a sergeant than Vipus. It was his resentment for Loken and his jealousy of Vipus that allowed a daemonic Warp-entity known as "Samus" to corrupt and possess him deep beneath the Whisperhead Mountains on the world of 63-19. Jubal killed his entire squad before attacking Loken and the accompanying members of Brakespur Squad. Loken restrained Jubal, but only after several members of Brakespur Squad were killed by their former Battle-Brother. The insipid powers of the Warp then mutated Jubal into the visage of a slobbering, raging Daemonhost. Jubal killed two Remembrancers who had arrived beneath the Whisperhead Mountains to document the Luna Wolves' latest victory before being torn apart by the Bolters of Loken and Vipus. Jubal was a member of the XVI Legion's warrior lodge, but had not attended any meetings in years at the time of his death, though Loken learned of the lodge's existence within his Legion when he went through Jubal's effects.
 * Talonus – Talonus was the Sergeant of the Pithraes Tactical Squad of the 10th Company.
 * Rassek – Rassek was a Terminator Squad Sergeant attached to the 10th Company. He was possibly a member of the elite Justaerin Terminator Squad of the 1st Company.
 * Kairus – Sergeant of the Walkure Tactical Squad of the 10th Company.
 * Luc Sedirae - Sedirae was the Captain of the 13th Company. An exceptional warrior, Sedirae's martial exploits were considered not far behind those of First Captain Ezekyle Abaddon. Sedirae was even considered at one point worthy of elevation into the esteemed ranks of the XVI Legion's elite Mournival, but was passed over in favour of Garviel Loken. The rumoured reason for this was that he was considered too ruthless in battle and too eager an advocate of unleashing warfare to bring worlds into Imperial Compliance when diplomacy would prove to be just as effective. Sedirae was later present on the planet Dagonet in the Segmentum Ultima during the early days of the Horus Heresy after the Sons of Horus had turned to the service of Chaos. Dagonet had been the site of one of Horus' first conquests of the Great Crusade, in which he claimed the planet for the Imperium with only a single Bolter shot. A lengthy civil war ensued between the Loyalist and Traitor factions on the world, with the pro-Horus aristocracy emerging as the dominant rulers of the planet. At the beginning of the Horus Heresy, Dagonet declared their allegiance to the Warmaster and invited him to attend a ceremony in his honour. But by this time, there had been a number of assassination attempts on the Warmaster's life by Loyalist Assassins. Therefore, Sedirae, acting as a body-double, wore Horus' Power Armour and descended to the planet's surface in the Warmaster's place. Upon removing his helm, a team of Imperial Assassins killed the false "Horus." The Sons of Horus were roused to a murderous rage and killed Dagonet's entire aristocracy, and then proceeded to vent their anger by exterminating the rest of the world's remaining population.
 * Jerrod - Replacement Captain of the 13th Company after Luc Sedirae was killed on the world of Dagonet while he was fulfilling his role as a body double for the real Horus and was assassinated by a special Officio Assassinorum strike team.
 * Tybalt Marr, "The Either" & Verulam Moy, "The Or" - Captains of the 18th and 19th Companies, respectively. Marr and Moy had an unusually close friendship with one another. They were amongst those Luna Wolves Battle-Brothers who looked very similar in physical appearance to their Primarch Horus, and were colloquially known as "Sons of Horus." Though notable for their striking resemblance to their Primarch, the similarities between the two were such (both physical and in the way in which they interacted with one another, and the similar styles in which they led their respective companies) that most within the Legion considered them almost as identical twins. Therefore, they were respectively referred to as the "The Either" and "The Or." Their companies often fought together in concert when circumstances permitted. It is interesting to note that Captain Moy was often placed in the speartip, the term used by the original Luna Wolves Legion as the initial assault element in any attack, while Captain Marr was not. It would be on Davin's moon that Captain Moy would meet his fate. Already a member of the warrior lodge and a capable line officer, Moy still hungered for the opportunity to distinguish himself as one of the elite Astartes of his Legion. When he was selected by the Warmaster to lead a speartip into the crashed flagship of the renegade Planetary Governor Eugen Temba, it appeared his opportunity for glory had finally arrived. Unfortunately, he was killed when he encountered the now Chaos-corrupted Temba after refusing his offer to submit to the corrupting influence of the Plague Lord Nurgle. The death of Moy affected Marr greatly, as he became sullen and withdrawn after visiting the scene of his friend's death. With Moy's death, Marr changed his mind about joining the XVI Legion's warrior lodge and so, on the eve of the Horus Heresy, he was inducted by Horus himself and followed his Legion to its eventual damnation.
 * Grael Noctua - Noctua was a Tactical Squad Sergeant assigned to the Sons of Horus' 25th Company during the Horus Heresy. Noctua was recommended to become a member of the Mournival by Captain Horus Aximand following the Battle of the Mausolytic Precinct on the planet Dwell to replace the Mournival members who had been lost on Istvaan III during the conflict between the Traitors and Loyalists within the Sons of Horus.
 * Lev Goshen - Captain of the 25th Company.
 * Kloros Endall - Lieutenant Endall was a Terran-born veteran of the XVI Legion. He was a part of the first wave of Loyalists during the assault on istvaan III's Choral City, and was presumably slain during the subsequent betrayal.
 * Dastruak Judd - Section-Leader Judd was a part of the Traitor attack forces unleashed against the Siren-Hold defences in the latter stages of the Istvaan III Atrocity, where he was slain by the Loyalist Sons of Horus Contemptor Dreadnought Ghrastak.
 * Guljuk Ygethddon - Sergeant Ygethddon commanded a Despoiler Squad of the 9th Battle Company, 2nd Battalion.
 * Zeb Zenonius - Sergeant of the Bale Tactical Squad of the 5th Company.
 * Eliphas the Inheritor - Eliphas was a former Dark Apostle of the Word Bearers Traitor Legion and leader of the XVII Legion's forces deployed for the Dark Crusade on the world of Kronus in the late 41st Millennium. On Kronus, Eliphas and his forces were defeated and slain by three companies of the Blood Ravens Space Marine Chapter under the command of Captain Davian Thule. After his soul suffered much torment in the Empyrean for his failure, he was resurrected by the will of the Chaos Gods to gain his revenge upon the Blood Ravens and left the Word Bearers behind to ally himself with the Black Legion and Abaddon the Despoiler following his return to life. He pledged to Abaddon that the destruction or corruption to Chaos of the Blood Ravens would be his only goal in life following his resurrection.
 * Avakhol Hurr - Hurr was a part of the XVI Legion's Rukal Breacher Battalion, which was primarily employed as a support assault contingent during boarding action and siege operations. The Rukal customarily practised the macabre preservation of any blood spray from their previous engagements on their armour as a visible sign of their destructive intent.
 * Severian - Severian was an Astartes of the 28th Company who was incarcerated in the prison of Khangba Marwu on Terra after the outbreak of the Horus Heresy. Severian escaped from the prison along with several other Astartes of the Crusader Host. Severian was last sighted in the Petitioner's City on Terra and his ultimate fate remains unknown.
 * Ghrastak (Deceased) - Ghrastak was a Cthonian by origin and a former Captain of the 13th Battle Company, but he remained a staunch devotee of the Emperor and of the ideals of Unification and so became a victim of Horus' conspiracy. Deployed via Drop Pod with the Loyalist Sons of Horus' first wave on Istvaan III, he was ultimately betrayed unto death fighting against the follow-on Traitor forces that ultimately culled the few remaining Loyalists after a two-month long siege.

Legion Fleet
The XVI Legion's Great Crusade fleet was accorded to be among the greatest under any single commander's flag, with in excess of one hundred capital ships and perhaps three times that figure in smaller Cruisers and Escorts under Horus' direct command. Taking into account likely losses from the ground war that followed the virus-bombing of Istvaan III, and elements of the Sons of Horus Legion not in the Istvaan System at the time, it would follow that Horus began his war of betrayal with around 70,000-110,000 Space Marines of his own Legion at his disposal, with considerable evidence present in Imperial records that the latter figure is the more accurate. The following starships are known to have been a part of the Black Legion's large fleet:
 * Vengeful Spirit (Gloriana-class Battleship) - The Vengeful Spirit was the infamous flagship of the XVI Legion and the Warmaster Horus during the Great Crusade and the Horus Heresy. It was upon this vessel that the final battle of the Heresy between the Emperor of Mankind and Horus played out and where the Warmaster's life and soul was finally extinguished by the unmatched psychic power of the Emperor. The Sons of Horus were able to recover their fallen Primarch's body before they fled the Sol System for the Eye of Terror and the Vengeful Spirit was taken by Horus' successor, Abaddon the Despoiler, as his own flagship. It still often serves in that function at the present.
 * Planet Killer (Unique Battleship) - The Planet Killer is a massive Chaos starship that served as flagship of Abaddon the Despoiler during the Gothic War and the 13th Black Crusade. The vessel owes its power to its main weapon, the Armageddon Gun, which can destroy an entire planet.
 * Harbinger of Doom (Battle Barge) - Formerly known as the Magna Tyrannis, this ancient Battle Barge has served the XVI Legion since the start of the Great Crusade until the end of the 41st Millenium. It has on multiple occasions served as the flagship of Abaddon the Despoiler.
 * Chariot of the Gods (Battleship, Unknown Class)
 * Forinox (Avenger-class Grand Cruiser
 * Leonis (Avenger-class Grand Cruiser)
 * Blade of Damnation (Repulsive-class Grand Cruiser)
 * Castigator (Vengeance-class Grand Cruiser)

Legion Colours
As if to mark a break from the wars of the past, the armour that the first warriors of the Space Marine Legions went to war in was cast in storm cloud grey, and bore only the thunderbolt and lightning marks of Imperial Unity. Over time the different Legions gained their own marks of distinction and character, as well as iconic names. When the XVI Legion were given the epithet of the "Luna Wolves" following the successful First Pacification of Luna campaign, they began to wear pale off-white ivory coloured Power Armour with black trim. The two renowned squads of the elite 1st Company, the Justaerin and Catulan Reavers, wore black coloured Power Armour, in sharp contrast to the white and later pale green of the rest of the Legion.

One avatar of the increasing influence of the Legion's Cthonian brothers was the late reemergence of Cthonian gang-sigils graven into a given Space Marine's armour that recorded his notable kills and deeds, as well as to which company of the Legion they belonged. This was a practice which accelerated rapidly after the XVI Legion had transitioned into its new identity as the Sons of Horus following the elevation of Horus to the rank of Warmaster. This transition marked not so much a new open brutality in the Legion, but a factor that had always been there and had become more visible as the Legion's panoply finally began to shrug off the influence of Mother Terra. The white of the Luna Wolves turned sea-green, then darkened further to a murky verdigris green-black as the Sons of Horus further cast off the discipline of the Terran traditions of warfare and erred in pride and growling malice towards the dark heart of Cthonia, and its traditions of gang-fiefdom, blood-pride and merciless, incessant conflict.

This colour scheme was retained until Abaddon the Despoiler took command of the Legion's remnants after the end of the Heresy and the Great Scouring. The renamed Black Legion, as the name suggests, wears predominately black Power Armour, similar to that once worn by Abaddon's owb elite formations of the 1st Company. The armour is decorated with gold trim and the standard Chaotic iconography. The shift of the XVI Legion's old colour scheme to its current black one was ordered by Abaddon to mark the Legion's shame and grief at the death of Horus after their failure to overthrow the Emperor of Mankind's rule during the Horus Heresy.

Legion Badge
The XVI Legion's badge was a wolf's head imposed over an inverted crescent moon when they were known as the Luna Wolves. The Legion badge changed to become a stylised eye over a cross -- the so-called Eye of Terra, which would later be known as the infamous "Eye of Horus" in the Imperium after the XVI Legion was renamed the Sons of Horus by the corrupted Warmaster. After the Sons of Horus were reconstituted following the Horus Heresy as the Black Legion, the symbol of the Eye of Horus was retained, however it was now superimposed over the eight-pointed Star of Chaos.

Gallery
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