Drop Site Massacre

"War is the crucible in which we burn. In the fires of battle is the past consumed and the future born on tongues of flame. No greater fire has there been in our times than the three bloody hours of the Dropsite Massacre."

- attributed to Malcador the Sigillite, Regent of Terra

The Drop Site Massacre of Istvaan V was one of the major turning points that occurred early in the great galactic civil war that engulfed the Imperium of Man in the early 31st Millennium that was known in later times as the Horus Heresy. After the news of the Istvaan III Atrocity was brought to the Emperor of Mankind by the Loyalists aboard the Death Guard Frigate Eisenstein, He ordered the combined forces of seven Space Marine Legions to assault the positions of Horus and his Traitor Legions in the Istvaan System. During that assault on the world of Istvaan V, three Loyalist Astartes Legions -- the Iron Hands, the Salamanders and the Raven Guard -- were betrayed by the 4 other Legions of the Loyalist second wave -- the Alpha Legion, Night Lords, Iron Warriors, and a large contingent of Word Bearers -- who they had believed were loyal to the Emperor of Mankind, but in fact had already betrayed the Imperium and secretly turned to the service of the rebellious Warmaster Horus and Chaos. As the Loyalists retreated back towards what they believed were friendly lines, the hidden Traitors revealed their allegiance by opening fire upon the Loyalists, catching them between a Traitor hammer and anvil and nearly destroying all three Loyalist Legions. This victory demolished what the Loyalists had believed to be their numerical superiority and opened the path to the conquest of Terra for Horus and his allies amongst the Forces of Chaos.

History
The Istvaan System’s third world, comfortably close enough to the Istvaanian sun to support human life, had become a virus-soaked mass grave marking the anger of Horus Lupercal in the aftermath of the Istvaan III Atrocity that marked the start of the Horus Heresy. The world’s population was nothing more than contaminated ash scattered over lifeless continents, while the bones of their cities remained as blackened smears of burnt stone – a civilisation reduced to memory in but a single day. The orbital bombardment from the Warmaster’s fleet, payloads composed of incendiary shells and virus-laden biological warfare pods, had seemingly spared nothing and no one anywhere on the world. Istvaan III lingered in silent orbit around its sun, almost grand in the extent of its absolute devastation, serving as the scarred tombstone for the death of an empire. With the destruction of the last surviving warriors on Istvaan III, the Traitor Legions of Horus made their way to Istvaan V, a flotilla of powerful warships and carriers bearing the martial pride of four Space Marine Legions, their ranks fully comprised of those whose loyalty was to Horus and Horus alone. Mass conveyors of Imperial Army units brought millions of armed men and their tanks and artillery pieces. Bloated Dark Mechanicum transports bore the Legio Mortis to Istvaan V, the dark Tech-priests ministering to the Dies Irae and its sister Titans as they prepared to unleash the unimaginable power of those war machines once more.

Final victory for the Traitors on Istvaan III had been bought with many lives, but in its wake the Traitor Legions were tempered in the crucible of combat to do what must be done to seize control of the Imperium. The process had been long and bloody, but the Warmaster's army was ready and eager to fight its brothers, where the lackeys of the Emperor would find their readiness to strike down their kith and kin untested. Such mercy would be their undoing, Horus promised. Horus would strike a vicious blow against the Imperium and the False Emperor -- a blow that would resonate down through the millennia for all time.

The Phoenician and The Gorgon
As Horus made the opening moves of his rebellion on Istvaan III, Ferrus Manus' oldest and dearest friend Fulgrim was ordered by the Warmaster to meet with the Iron Hands' Primarch aboard his flagship Fist of Iron in the hope that he could be swayed to the side of the Traitor Legions who now served Chaos. Fulgrim had sent the bulk of his III Legion and the 28th Expeditionary Fleet on to meet Horus and the 63rd Expeditionary Fleet in the Istvaan System while he and a small force aided the Iron Hands' 52nd Expeditionary Fleet in retaking the world of Callinedes IV from Orks. Great bonds of friendship and brotherhood had long existed between the two Legions, and Fulgrim felt that he could convince Ferrus of the righteousness of Horus' cause. Fulgrim's hope proved disastrously wrong and the meeting of the two Primarchs in Ferrus' private inner sanctum in his flagship's Anvilarium did not go well, as Ferrus was utterly outraged that his brothers would turn against their father the Emperor. The meeting ended in violence as The Gorgon made his difference of opinion over continued loyalty to the Emperor known to the Phoenician with his weapons, determined to stop Fulgrim's betrayal of the Imperium before it could begin. Ferrus attempted to use his silvery necrodermis hands to destroy Fulgrim's golden sword Fireblade, but the resulting explosion knocked him unconscious.

Fulgrim intended to kill his unconscious brother with the weapon he had forged for him, the warhammer Forgebreaker, but proved unable to kill his oldest friend despite the promptings of the Slaaneshi daemon that now corrupted his soul. Instead he took the wonderous weapon that he had once crafted in brotherhood for Ferrus as a reminder of their former friendship, and left behind Fireblade, which Ferrus had forged for him. When Fulgrim emerged from Ferrus' inner sanctum, he gave a signal to his elite Phoenix Guard, who instantly beheaded all of the Iron Hands Morlocks Terminators who served as Ferrus' own elite bodyguard with their Power Halberds. The Emperor's Children also nearly slew the Iron Hands' First Captain Gabriel Santor. Fulgrim successfully fled the Iron Hands' expeditionary fleet in his personal assault craft, the Firebird, as he ordered his warships, the Battle Barge Pride of the Emperor and its Escorts, to open fire upon the ships of the Iron Hands' 52nd Expeditionary Fleet. This surprise attack crippled the Iron Hands force and provided a distraction while Fulgrim and the Emperor's Children warships fled into the Warp to rendezvous with the rest of their 28th Expeditionary Fleet in the Istvaan System.

The Warmaster was enraged at Fulgrim's failure at converting their brother Ferrus to their cause. Nevertheless, he still had to make preparations for the inevitable response of the Emperor, which was likely to arrive more quickly than anticipated and the Traitors needed to be prepared for it. Fulgrim was tasked to take a detail of Emperor's Children to the ruins of the alien fortresses that existed on Istvaan V and prepare that world for the final phase of the Istvaan operation. Though the Phoenician recoiled at the horrifying prospect of the menial role placed upon him, Horus explained that the Istvaan V phase of his plan was the most critical, and he could entrust this vital task to no other. Fulgrim supervised the vast teams of Dark Mechanicus earthmovers as they shifted the black sand of Istvaan V and formed a vast network of earthworks, trenches, bunkers and redoubts that stretched along the ridge of the Urgall Plateau. Laagers of anti-aircraft batteries were set up in the shadow of the walls, and mighty orbital torpedoes on mobile launch vehicles hid in the warrens of an ancient alien fortress. Fulgrim had set up his command within the remains of the keep and begun the work of ensuring that it would be a bastion worthy of the Warmaster. If the Emperor’s Legions wanted to destroy the Traitors, they were going to have to come down to the surface of Istvaan V to do so, as no obital bombardment would be powerful enough to dislodge the defenders or crack their resolve.

Mobilising for War
"And the voice of his brother's blood shall cry unto him from the ground and demand vengeance..."

- Auto-lingua transcription, Astropathic Conduit Trans-Episolon Thule, Sol-Lorin Relay

Overcome with mind-numbing rage at their brothers' treachery, Ferrus and his warriors gratefully received the Emperor's orders through his brother Rogal Dorn. In response to Horus' betrayal of the Loyalist Astartes in the Sons of Horus, Emperor's Children, World Eaters and Death Guard Legions at Istvaan III, the Primarch of the Imperial Fists Legion, Rogal Dorn, on the direction of the Emperor who had learned of Horus' actions from the Loyalist survivors aboard the Eisenstein. The forces of no fewer than eight Legions had been despatched by Rogal Dorn as acting Magister Militum of the Imperium to crush Horus' rebellion on the world of Istvaan V. They would attack in two waves and fall under the supreme command of the Iron Hands' Primarch Ferrus Manus. The Legions comprising the first wave were the Iron Hands, Salamanders, and the Raven Guard. The Legions comprising the second wave, who would arrive at Istvaan V after the first wave, were the Alpha Legion, Night Lords, Iron Warriors, and a large contingent of Word Bearers that their Primarch Lorgar had stationed in the star system. Also, a large fleet contingent of Dorn's own Imperial Fists were dispatched to investigate Garro's earlier claims. Unknown to Dorn and Ferrus Manus, the Night Lords, Alpha Legion, Iron Warriors and Word Bearers had all turned from their service to the Emperor and pledged their loyalty to Horus, and been instructed to keep their new allegiance to Chaos a secret. Owing to turbulence within the Warp, the Imperial Fists were becalmed and prevented from reaching their goal, but the others made great haste and through a masterful application of astropathic co-ordination and favourable transit, the avenging forces of the Emperor made swift speed to their target, with the forerunners being the Salamanders and Raven Guard fleets and their attendant forces, with the others following close behind. In the cold light of retrospective vision, this list of seemingly co-incidental facts: the thwarting of the Imperial Fists fleet, the ease of passage for the others, which Legions should approach the Istvaan System first, all took on a malign and sinister predestination. In this ordering of events could later be seen the hand of dark forces from beyond, forces which once Mankind slept in blissful ignorance of, but of whose truth the Imperium would later learn at such great cost.

It is important to note that at this early stage of the great conflict, the full scale and rank horror of Horus' betrayal were yet to unfold, and both his motivations and the murderous depth of his ambition remained unclear, while the Imperium believed wholeheartedly that it had the upper hand both in matériel strength and capacity to act. There were those among the Loyalists still utterly baffled by what could have triggered the Warmaster's perfidy, and in the private councils of those who knew of the matter -- which was still far from common knowledge -- as the punishment fleet was sent to bring the Traitors to justice, talk of mental breakdown or megalomaniacal insanity on Horus' part, or even the cancerous control of some hideous alien form such as the Khrave or the Enslavers was common speculation as to the cause of this sudden treachery. Regardless of this confusion as to its genesis, the judgement of the Imperium was to be swift and savage in its execution, and Horus' rebellion, swaying as it had four Space Marine Legion to his cause, was judged more dangerous than any that had gone before it during the Great Crusade (and indeed there had been several such), but it was also generally thought that Horus would content himself with carving out an empire of his own as the Throne's rival. Although clearly a false assumption in hindsight, with this hypothesis in mind, the selection of Istvaan -- a strategically significant system, seated at the confluence of several known stable Warp routes, but one also far distant from the seat of the Imperium's power -- as a base for this treacherous domain made a certain sense. As did the wisdom of immediate attack before the Traitors' stronghold could be properly established.

Invasion
As the Loyalists closed on the Istvaan System, it received the target's information relayed by astropathic transmission. It was received with a mixture of bellicose fervour and some trepidation. Given the scale of concealed activity on Istvaan V, it was clear that the enemy was rearing up a fortress of prodigious strength there, no doubt intended to be the headquarters of the Warmaster's rebellion and its principal mustering ground. The absence of the Traitors' fleet, however, was a more troubling matter, but one perhaps easily explained by a needful scramble for resources and supply from distant systems in preparation for a conflict to come, and if indeed the Traitors were sure that no sizable counter-attack could yet be attempted upon them, such a brave gamble was in-keeping with the Warmaster's known character. Long-range pict-captures showed the personal standards of both Horus and Fulgrim flying above the overbuilt ancient fortifications of Istvaan V's Urgall ruins, while power armoured figures and Mechanicum engines toiled ceaselessly to raise up defences beneath them, and this damning evidence above all else settled the fate of what was to come.

For Ferrus Manus, the absence of the Traitor Legion's fleet in the Istvaan System was not so much a cause of suspicion as it was an opportunity that should not be wasted. Through the bungled attempt of Fulgrim and his Emperor's Children to sway Ferrus Manus to the Traitors' cause and the flight of the Eisenstein escaping the betrayal at Istvaan III, the Imperium had been made aware of the Warmaster's plot long before the arch-traitor had been ready, and to the grim mind of the master of the Iron Hands, it was an error for which the enemy would be made to pay. The time to strike was now, before the enemy fleet returned, and crush the rebellion with a single concerted attack. It was a judgement shared by many; they had caught the Traitors' preparations in disarray -- the Warmaster's dispositions half-made and his defences incomplete. The enemy was vulnerable or so the Loyalists thought. Soon the cataclysm would be unleashed, and the war of the Horus Heresy would truly begin.

Traitor Conclave
"Mark this day well, my friends. The Emperor's loyalists are heading to their doom!"

- Warmaster Horus remarking to Primarchs Angron and Fulgrim during the initial Loyalist assault on Istvaan V

Ringing Istvaan V was one of the largest fleets ever gathered in the history of the human species. Without a doubt, it was the most impressive coalition of Astartes vessels ever gathered, with the scouts, cruisers, destroyers and command ships of seven entire Legions present. Shuttles and gunships ferried between the heaviest cruisers, while the decks of every warship made ready to deploy their warriors in an unprecedented, unified planetfall. Horus had decided to make his stand on the surface. The Imperium of Man had sent seven Legions to kill its wayward scion, little knowing that four of them had already spat on their oaths of allegiance to the Imperial Throneworld and its master.

The Fidelitas Lex, Lorgar's flagship, played host to a gathering of rare significance. There were commanders from the Night Lords, Alpha Legion, Iron Warriors as well as three additional Primarchs: Konrad Curze, Alpharius Omegon and Perturabo. Lorgar strode to the centre of the gathering of Traitors. He proceeded to impress upon the gathering of his sons, brothers and cousin Astartes the importance of their cause, and of the significance this day would hold in history. The Word Bearers and their allies believed that the Imperium had failed them by being flawed to its core, imperfect in its pursuit of a perfect culture, and in its weakness against the encroachment of xenos breeds that sought to twist humanity to alien ends. And it had failed them, most of all, by being founded upon the lies of rationalism and atheism that defined the Imperial Truth. The Imperium had been forged under the aegis of a dangerous deceit, demanding that its citizens and their defenders sacrifice truth on the altar of necessity. This was an empire that deserved to die. And on Isstvan V the purge would begin.

From the ashes Lorgar promised would rise the new kingdom of Mankind: an Imperium of justice, faith and enlightenment. An Imperium heralded, commanded and protected by the avatars of the Gods themselves. An empire strong enough to stand through a future of blood and fire. But now the Traitors would declare their intentions openly. There would be no more manipulating fleet movements and falsifying expeditionary data. Now the Alpha Legion, the Word Bearers, the Iron Warriors and the Night Lords would stand together with their comrades in the Sons of Horus, World Eaters, Emperor's Children and Death Guard Legions – bloodied but unbowed beneath the flag of the Warmaster Horus, the rightful second Emperor of Mankind. The true Emperor. When Lorgar had finished speaking, First Captain Sevatar of the Night Lords Legion declared, "Death to the False Emperor!" In so doing, he became the first living soul to utter those words that would echo from the throats of countless others through the millennia of the Long War that was to come. The cry was taken up by other voices, and soon it was cried in full-throated roars, "Death to the False Emperor! Death to the False Emperor! Death! Death! Death!"

Initial Assault
"I can scarcely imagine what inspired Horus to this madness. In truth, the very fact of it frightens me. For if even the best of us can falter, what does that mean for the rest? Lord Manus will lead us in. Seven Legions against his four. Horus will regret this rebellion."

- Vulkan, Primarch of the Salamanders Legion

The warriors of the World Eaters, Death Guard, Sons of Horus and Emperor’s Children had deployed throughout the defences constructed along the ridge of the Urgall Depression, making ready for the howling storm of battle that was soon to descend upon them. Behind them, long range support squads manned the walls of the fortress, and Traitor Army artillery pieces waited to shower any attacker with high explosive death. The Dies Irae stood before the wall, its colossal guns primed and ready to visit destruction on the enemies of the Warmaster. Nearly 30,000 Astartes hunkered down on the northern edge of the Urgall, their guns ready and their hearts steeled to the necessity of what must come.

The first warning came when a dull, red orange glow built behind the clouds, bathing the Urgall in a fiery light. Then came the sound: a low roar that built from a deep, thrumming bass to a shrieking whine. Alarms sounded and the clouds split apart as individual streaks of light burned through and fell in a cascading torrent of fire. Thunderous explosions ripped along the edge of the Urgall, and the entire length of the Warmaster’s forces was engulfed in a searing, roaring bombardment. For long minutes, the forces of the Emperor that had just moved into orbit over Istvaan V pounded the Urgall Plateau from orbit, a firestorm of unimaginable ferocity hammering the surface of Istvaan V with the power of the world’s end. Eventually, the horrific bombardment ceased and the drifting echoes of its power faded, along with the acrid smoke of explosions, but the Emperor’s Children had performed perfectly in creating a network of defences from which to face their former brothers, and the forces of the Warmaster had been well-protected. From his vantage point in the alien-built keep, Horus smiled, and he watched the sky darken once again as thousands upon thousands of Drop Pods and Stormbirds streaked through the atmosphere towards the planet’s surface to carry out the initial Loyalist assault. The first wave was under the overall command of the Primarch Ferrus Manus and besides his own X Legion, the Salamanders led by Vulkan and the Raven Guard under the command of their Primarch Corax joined him. Vulkan's Legion assaulted the left flank of the Traitors' battle line while Ferrus Manus, the Iron Hands' First Captain Gabriel Santor, and 10 full companies of elite Morlocks Terminators charged straight into the centre of the enemy lines. Meanwhile, Corax's Legion hit the right flank of the enemy's position. The odds were considered equal: 30,000 Traitor Marines against 40,000 Loyalists. Horus was aware of the location of the Loyalists' chosen drop site and his troops fell upon the Loyalist Legions. The battlefield of Istvaan V was a slaughterhouse of epic proportions. Treacherous warriors twisted by hatred fought their former brothers-in-arms in a conflict unparalleled in its bitterness. The mighty Titan war engines of the Machine God walked the planet’s surface and death followed in their wake. The blood of heroes and traitors flowed in rivers, and the hooded Heretek Adepts of the Dark Mechanicum unleashed perversions of ancient technology stolen from the Auretian Technocracy to wreak bloody havoc amongst the Loyalists. Hundreds, perhaps even thousands of Traitors had been slaughtered in the opening moments of the assault. All across the Urgall Depression, hundreds died with every passing second, the promise of inevitable death a pall of darkness that hung over every warrior. Thousands were dying every minute, the slaughter terrible to behold. Blood ran in rivers down the slopes of the Urgall Depression, carving thick, sticky runnels in the dark sand. Such destruction had never yet been concentrated in such a horrifically confined space, enough martial power to conquer an entire planetary system having been unleashed in a line less than twenty kilometres wide.

The slaughter continued unabated, on a scale never before seen, with neither side able to press home their advantages. The Traitors were well dug-in and had defensible positions, but the Loyalists had landed almost directly on top of them with numerical superiority. The bloodletting was a truly horrific sight as warriors who had once sworn great oaths of loyalty to one another fought their brothers with nothing but hatred in their hearts. No Legion fared well in the slaughter, as the scale of the fighting rendered tactics meaningless as the two armies battered each other bloody in a remorseless conflict that threatened to destroy them all. The Traitor forces held, but their line was bending beneath the fury of the first Loyalist assault. It would take only the smallest twists of fate for it to break. The forces on the surface were in combat for almost three hours with no clear victor emerging. The Loyalists waited for the second wave of "allies" to make planetfall, believing they would be reinforced for their final advance. The Traitors all knew the parts they had to play in this deadly performance. They were all aware of the blood they needed to shed to install Horus as the Master of Mankind.

Battle of the Urgall Depression
"This is not victory, it is death. It is bonds broken and bloody. And it shall mark us all for generations."

- Vulkan, Primarch of the Salamanders Legion

Though the Iron Hands, Raven Guard and Salamanders had managed to make a full combat drop and secure the Loyalist drop site, known as the Urgall Depression, they did so at a heavy cost. What had begun as a massed strike against the Traitors’ position was rapidly turning into one of the largest engagements of the entire Great Crusade. All told, over 60,000 Astartes warriors clashed on the dusky plains of Istvaan V. For all the wrong reasons, this battle was soon to go down in the annals of Imperial history as one of the most epic confrontations ever fought. Where one side lost ground in one place, it gained in another, and the battle lines shifted again and again, with no advantage pressed home on either side in the wake of such utter destruction wrought by both. The black sands ran red with blood. Tens of thousands of Space Marines had died in a little over two hours of battle; a cataclysm never before seen in open conflict, and tens of thousands more fought on, brutalised and injured. Such was the mind-shattering tumult, that scores of human auxiliaries, hardened even as they were by the wars of the Great Crusade, simply fell to their knees paralysed in terror, or became crazed and had to be shot down by their overseers, lest they endanger their comrades. Slowly, inexorably, the Traitor lines began to bow dangerously backward. As the slaughter at the fortress-line continued unabated, at the rearmost part of the Urgall Depression a vast crimson bulk had slowly descended, anti-aircraft fire stitching blackened scorches across its cylindrical armoured sides. It was a battle-maniple of the Legio Atarus, the Firebrands Titan Legion in their macro-lander, and their arrival had been warranted by the heart bloom-signatures of others of their kind advancing through the billowing dust storm from the desert plains. The Legio Mortis was approaching also, and at their colossal striding feet raced scores of Predator tanks and Outrider and Jetbike squadrons drawn from the Sons of Horus and World Eaters Legions. The auguries showed the Legio Atarus was outnumbered and outclassed. For the Legio Atarus, the chance to attack their erstwhile brethren of the Legio Mortis was not merely the desire of those who had stayed loyal to punish the Traitor, but the culmination of a long-simmering grudge that had its roots decades before this day. So it was that with righteous anger that the Titans of the Legio Atarus sounded their great sirens and charged into battle against their foe, and in doing so became the first Loyalist Titan Legio in the war of the Horus Heresy. The battle that followed was brief but brutal. At the cost of their own complete destruction, the Firebrands' counter-attack effectively neutralized the secondary Legio Mortis contingent. The delayed and badly mauled Traitor Legion flanking force was then systematically destroyed by the Iron Hands subjugator group. The Urgall Depression was churned to ruination beneath the boots and tank treads of countless thousands of Astartes warriors and their Legion’s armour divisions. The Loyalist Primarchs could be found where the fighting was thickest: Corax of the Raven Guard, borne aloft on black wings bound to a fire-breathing flight pack; Lord Ferrus of the Iron Hands at the heart of the battlefield, his silver hands crushing any Traitors that came within reach, while he pursued and dragged back those who sought to withdraw; and lastly, Vulkan of the Salamanders, armoured in overlapping Artificer plating, thunder clapping from his warhammer as it pounded into yielding armour, shattering it like porcelain. The traitorous Primarchs slew in mirror image to their brothers: Angron of the World Eaters hewing with wild abandon as he raked his Chainaxes left and right, barely cognizant of who fell before him; Fulgrim of the lamentably-named Emperor’s Children, laughing as he deflected the clumsy sweeps of Iron Hands warriors, never stopping in his graceful movements for even a moment; Mortarion of the Death Guard, in disgusting echo of ancient Terran myth, harvesting life with each reaving sweep of his great Warscythe. And then there was Horus, the Warmaster of the Imperium, the brightest star and greatest of the Emperor’s sons. He stood watching the destruction while his Legions took to the field, their liege lord content in his fortress rising from the far edge of the ravine. He was shielded and unseen by his brothers still waging war in the Emperor’s name. At last, above this maelstrom of grinding ceramite, booming tank cannons and chattering Bolters -- the gunships, Drop Pods and assault landers of the second Loyalist wave burned through the atmosphere on screaming thrusters. The sky fell dark as the weak sun was eclipsed by ten thousand avian shadows, and the cheering roar sent up by the Loyalists at the arrival of their comrades was loud enough to shake the air itself. Like fiery comets from the heavens, the thrusters of countless drop-ships, landers and assault craft broke through the fire-shot clouds of smoke and descended to the Loyalist landing zone on the northern edge of the Urgall Depression. Hundreds of Stormbirds and Thunderhawks roared towards the surface, their armoured hulls gleaming as the power of another four Legiones Astartes came to Istvaan, their heroic names legendary, their mighty deeds known the length and breadth of the galaxy: the Alpha Legion, Word Bearers, Night Lords, and Iron Warriors.

The Traitors, the bloodied and battered Legions loyal to Horus, fell into a fighting withdrawal without hesitation. Overwhelmed with rage, the headstrong Ferrus Manus disregarded the counsel of his brothers Corax and Vulkan and hurled himself against the fleeing rebels, seeking to bring Fulgrim to personal combat. His veteran troops -- comprising the majority of the X Legion's Terminators and Dreadnoughts -- followed.

Treachery Most Foul
"When the traitor's hand strikes, it strikes with the strength of a Legion."

- Warmaster Horus, after the Istvaan V massacre

The second wave of "Loyalist" Space Marine Legions descended upon the landing zone on the northern edge of the Urgall Depression. Hundreds of Stormbirds and Thunderhawks roared towards the surface, their armoured hulls gleaming as the power of another four Astartes Legions arrived on Istvaan V. Yet the Space Marine Legions of the reserve were no longer loyal to the Emperor, having already secretly sworn themselves to Chaos and the cause of Horus. The Night Lords of Konrad Curze, the Iron Warriors of Perturabo, the Word Bearers of Lorgar Aurelian, and the Alpha Legion of Alpharius represented a force larger than that which had first begun the assault on Istvaan V. The secret Traitor Legions mustered in the landing zone, armed and ready for battle, unbloodied and fresh.

The Iron Warriors had claimed the highest ground, taking the Loyalist landing site with all the appearance of reinforcing it through the erection of prefabricated plasteel bunkers. Bulk landers dropped the needed battlefield architecture: dense metal frames fell from the cargo claws of carrier ships at low altitude, and as the platforms crashed and embedded themselves in the ground, the craftsmen-warriors of the IV Legion worked, affixed, bolted and constructed them into hastily-rising firebases. Turrets rose from their protective housing in the hundreds, while hordes of lobotomised Servitors trundled from the holds of Iron Warriors troopships, single-minded in their intent to link with the weapons systems’ interfaces. The Word Bearers bolstered their brother Legions on one flank of the Urgall Depression while the Night Lords took positions on the opposite side. Down the line, past the mounting masses of Iron Warriors battle tanks and assembling Astartes, First Captain Sevatar of the Night Lords and his 1st Company elite, the Atramentar, took up defensive positions. Both the Word Bearers and the Night Lords were to be the anvil, while the Iron Warriors would be the hammer yet to fall. The enemy would stagger back to them, exhausted, clutching empty Bolters and broken blades, believing their presence to be a reprieve.

It is held by some sources that, upon the arrival of the four fresh Legions, Corax, the usually taciturn Primarch of the Raven Guard, was the first to call for a withdrawal for those fighting in favour of the newcomers to take the lead. His Legion had suffered severely in the battle, as had all the combatants, and he had no desire to waste further lives in pointless attrition, where stronger forces, yet un-bloodied might take to the fore. Vulkan was also in favour of consolidation, his Legion having seen some of the most relentless and savage fighting against the Death Guard. The dark weapons of the XIV Legion had inflicted a great many casualties and almost all of Vulkan's warriors were counted among the fighting wounded, their munitions all but spent. Dragging their wounded and dead behind them, Corax and Vulkan led their forces back to the drop site to regroup and to allow the warriors of their recently arrived brother Primarchs of the second wave a measure of the glory in defeating Horus. Though they Voxed hails requesting medical aid and supply, the line of newly-arrived Astartes atop the northern ridge remained grimly silent as the exhausted warriors of the Raven Guard and Salamanders came to within a hundred metres of their allies. It was then that Horus revealed his perfidy and sprung his lethal trap. Inside the black alien fortress where Horus had made his lair, a lone flare shot skyward, exploding in a hellish red glow that lit the battlefield below. The fire of betrayal roared from the barrels of a thousand guns, as the second wave of Astartes revealed where their true loyalties now lay. The Loyalists' supposed "allies" opened fire upon the Salamanders and Raven Guard, killing hundreds in the fury of the first few moments, hundreds more in the seconds following, as volley after volley of Bolter fire and missiles scythed through their unsuspecting ranks. Even as terrifying carnage was being wreaked upon the Loyalists below, the retreating forces of the Warmaster turned and brought their weapons to bear on the enemy warriors within their midst. Hundreds of World Eaters, Sons of Horus and Death Guard Astartes fell upon the veteran companies of the Iron Hands, and though the warriors of the X Legion continued to fight gallantly, they were hopelessly outnumbered and would soon be hacked to pieces. The Iron Hands had damned themselves by remaining in the field instead of retreating like their fellows.

The Raven Guard's front ranks went down as if scythed, harvested in a spilling line of detonating Bolter shells, shattered armour and puffs of bloody mist. Black-armoured Astartes tumbled to their hands and knees, only to be cut down by the sustained volley, finishing those who fell beneath the initial storm of head- and chest-shots. Seconds after the first chatter of Bolters, achingly bright laser beams slashed from behind the Word Bearers as the cannon mounts of Land Raiders, Predators and defensive bastion turrets gouged through the Raven Guard and the ground they stood upon. The Iron Warriors and Word Bearers kept reloading, opening fire again, hurling grenades and then preparing to fall back. The Word Bearers Legion had taken up landing positions on the west of the field, ready to sweep down and engage the Raven Guard from the flank. Three figures stood atop the roof of an ornate command tank, the Land Raider’s bronze and grey armour decked out with flapping banners and etched with fingernail-fine scripture over every visible surface. Kor Phaeron, Master of the Faith, watched the distant dropsite through a desperate squint. The Word bearers First Chaplain Erebus, the architect of Horus' fall to Chaos, stood at his side.

Lorgar towered above both of them, but had no attention to spare for the treacherous opening salvoes against the warriors of the Raven Guard and Salamanders Legions. He stared into the battlefield’s heart, his eyes wide even in the wind, his lips gently parted as he watched his brothers killing each other. Fulgrim and Ferrus, the fading sunlight flaring from the edges of their swinging weapons. The wind stole the clash and clang of their parries, but even in silence the duel was beyond captivating. No human senses save those as acute as a Primarch’s could have followed such instant, liquid movements. The perfection of it all almost brought a smile to Lorgar's lips. As the Primarch watched his two brothers engaged in their furious duel, he recalled a time long before when Ferrus had presented him with a weapon he had personally forged. Ferrus had crafted the fine crozius-maul, Illuminarum, as thanks for the reinforcement of the X Legion by the Emperor's Children at Galadon Secondus. Snapping back to reality, the seed of doubt crept into Lorgar as he played witness to the slaughter around him. But with the prodding and reassurance of his adopted father Kor Phaeron, Lorgar ordered his Word Bearers to attack.

At point blank range the unsuspecting Legionaries of the Salamanders and the Raven Guard were cut down by the hundred by those they thought their brothers. Battered tanks and Dreadnoughts that had weathered the storm of three hours of the most hellish combat the Legiones Astartes had ever seen were caught in a blizzard of missile and lascannon fire form those they expected to be allies, their explosive pyres igniting in droves up and down the Loyalist battle line. Night Lords gunships raked across the sky, raining down phosphex and cluster munitions, screaming Raptors following in their wake, and without warning the Alpha Legion were in among the hastily set-up apothecarion stations of the rear echelon, murdering with ruthless efficiency, while their fast-moving armour and mechanised squads encircled the Salamanders before slicing into them with a surgeon's precision. From behind the steel-clad emplacements of the Iron Warriors, the vaunted artillery of the Stor-Bezashk spoke, their deadly Scoprius pattern Whirlwinds and Minotaur siege guns laying waste to the stunned Imperial Army battalions and ravaging the first wave's landing zones, while their Cerberus and Typhon tanks advanced to rip apart the Imperial Army's super-heavy tanks at close-quarters.

Dropsite Massacre
"Alone, a Legionary is a formidable foe as far beyond a man as the wolf is beyond the sheep. Together, bound by ties of unshakeable loyalty, a Legion is a force that can extinguish the stars and shake the very heavens."

- Lorgar Aurelian, Primarch of the Word Bearers

Taking stock of their dire situation, the Primarchs Corax and Vulkan differed over how to salvage what they could from the situation. The Salamanders' Primarch suggested that the Loyalists attempt to make a tactical withdrawal to their respective drop ships and dig in to resist any further attacks. Corax advocated instead that the Loyalists should do whatever they could to make good their escape from the slaughter as the battle was lost. Neither Primarch could agree with the other, and so Corax turned from Vulkan and ordered his Legion to retreat. A short while later, a direct artillery strike hit the Primarchs' position. By the grace of the Emperor, Corax somehow managed to survive, but the fate of his brother Vulkan was unknown. In the meantime, the second wave of Traitor Legions that had turned upon their former allies began to slaughter the Loyalists in earnest. The Iron Hands were apparently slaughtered to a man. In the midst of this brutal carnage, two Primarchs from the opposing sides confronted one another in a final showdown. Fulgrim of the Emperor's Children and Ferrus Manus, once as close as true brothers could be, fought a bitterly contested, titanic struggle.

The Death of Ferrus Manus
Ferrus Manus and his Morlocks had charged through the shattered ruin of the Traitors' defences before the second wave had arrived, his black armour and their burnished plates scarred and stained with the blood of enemies. Fulgrim’s fixed smile faltered as he truly appreciated the depths of hatred his brother held for him and wondered again how they had come to this point, knowing that any chance for brotherhood was lost. Only in death would their rivalry end. The Iron Hands pushed through the defences, the bulky Terminators unstoppable in their relentless advance. Lightning crackled from the claws of their gauntlets and their red eyes shone with anger. The Phoenix Guard braced themselves to meet the charge, fully aware of the power such mighty suits of armour granted to their wearers. The Phoenix Guard answered with a terrible war cry and leapt to meet the Morlocks in a searing clash of blades. Electric fire leapt from the golden edges of the halberds and the Lightning Claws of the warriors, and a storm of light and sound flared from each life and death struggle. The battle engulfed the Primarch of the Emperor’s Children, but he stood above it, awaiting the dark armoured giant who strode untouched through the lightning shot carnage as brothers hacked at one another in hatred. Ferrus had long dreamt of this moment of reckoning, ever since Fulgrim had come to him with betrayal in his heart. Only one of them would walk away from their final confrontation.

Ferrus taunted Fulgrim for his betrayal of the Emperor and siding with the Traitor Horus. He thought his brother mad, for the Warmaster was defeated—his forces routed and the power of another four Legions would soon be brought to bear to crush their attempt at rebellion utterly. Unable to contain himself any longer, Fulgrim shook his head, savouring the final act of betrayal to come, revealing to Ferrus that it was he who was naive. Horus would never be foolish enough to trap himself like this. He pointed out towards the northern edge of the Urgall Depression so that Ferrus could see that it was he and his fellow Loyalists who were undone. Ferrus looked and saw a force larger than that which had begun the assault during the first wave of attack, mustered in the landing zone, armed and ready for battle.

Ferrus looked on in stunned horror as Fulgrim laughed at the look on his brother's face as the forces of his "allies" opened fire upon the retreating Salamanders and Raven Guard, killing hundreds in the fury of the first few moments, hundreds more in the seconds following, as volley after volley of Bolter fire and missiles scythed through their unsuspecting ranks. Even as terrifying carnage was being wreaked upon the Loyalists below, the retreating forces of the Warmaster suddenly turned and brought their weapons to bear on the enemy warriors within their midst. Hundreds of World Eaters, Sons of Horus and the Death Guard fell upon the veteran companies of the Iron Hands, and though the warriors of the X Legion continued to fight gallantly, they were hopelessly outnumbered and would soon be hacked to pieces. Ferrus Manus turned to face Fulgrim, his teeth bared with the volcanic fury of his homeworld of Medusa. The two Primarchs leapt at one anther, Ferrus wielding Fireblade and Fulgrim holding Forgebreaker. Their weapons had been forged in brotherhood, but were now wielded in vengeance, meeting in a blazing plume of energy. The two Primarchs traded blows with their monstrously powerful weapons. Ferrus Manus wielded his flaming blade in fiery slashes, his every blow defeated by the ebony hafted hammer now wielded by his brother that he had once borne in countless campaigns. Both warriors fought with the hatred only brothers divided could muster, their armour dented, torn and blackened by their fury.

The two Primarchs traded terrible blows, wounding one another deeply during their fierce struggle. As Ferrus pushed himself to his feet and staggered towards the wounded Fulgrim, he cried out as he brought the flaming blade towards his brother's neck. But Fulgrim lashed out as he drew the single-edged, daemonically-possessed sword he had taken from the Laer temple dedicated to Slaanesh on Laeran and blocked the descending weapon. With the power of Chaos streaming from the blade, diabolical strength flooded Fulgrim's limbs as he pushed against the power of Ferrus Manus, feeling his brother's surprise at his resistance. Fulgrim managed to surge to his feet and lashed out, his silver blade biting deep into the breastplate of Ferrus' armour, and the Primarch of the Iron Hands cried out, falling to his knees once again. Fireblade slid from his grasp as he gasped in fierce agony. As Fulgrim raised the silver sword in preparation to deliver the coup de grace to Ferrus Manus, he found that he did not possess the fortitude to deliver the killing blow. In an instant he saw what he had become and what monstrous betrayal he had allowed himself to be a willing party to. Fulgrim knew in that eternal moment that he had made a terrible mistake in drawing the sword from the Temple of the Laer, and he fought to release the damnable blade that had brought him so low.

His grip was locked onto the weapon and even as he recognised how far he had fallen, he knew that he had come too far to stop, the realisation coupled with the knowledge that everything he had striven for had been a lie. As though moving in slow motion, Fulgrim saw Ferrus Manus reaching for his fallen sword, his fingers closing around the wire-wound grip, the flames leaping once more to the blade at its creator’s touch. Fulgrim’s blade seemed to move with a life of its own as he swung the blade of his own volition. Fulgrim tried desperately to pull the blow, but his muscles were no longer his own to control. The daemonic blade sliced through the genetically-enhanced flesh and bone of one of the Emperor's sons. The Iron Hands' Primarch fell to the ground, his head decapitated. Ferrus Manus was dead by his brother's own hand and his Legion would nearly share his fate.

The Raven and the Urizen Clash
On the other end of the battlefield from the duel between Fulgrim and Ferrus Manus, the Raven Guard were confronted by the treacherous Word Bearers, with their Primarch Lorgar, the First Captain Kor Phaeron and the First Chaplain Erebus at their vanguard. The two Legions fought one another in bitter combat. In the midst of this battle, the Word Bearers unleashed the elite unit known as the Gal Vorbak -- Astartes who had allowed themselves to be possessed by daemons. They attacked the Raven Guard's Primarch en masse, but despite the advantage of their numbers, Corax's formidable abilities as a consummate warrior proved to be more than a match for the possessed Astartes, and he slew them with impunity. Seeing the slaughter of his most favoured sons, Lorgar intervened and prevented the death of the remaining Gal Vorbak Astartes.

Amidst the carnage and the slaughter, the anger of a demigod was released -- beyond anger, beyond rage. It went beyond both, for it was wrath, in physical form. Corax charged into the ranks of the Traitorous Word Bearers, a blur of charcoal armour and black blades, butchering with an ease that belied his ferocity. Soon the voices of dying Word Bearers became a conflicting chorus over the Vox as they screamed for help. Argel Tal, the Crimson Lord and leader of the daemon-possessed Gal Vorbak, Lorgar's "Blessed Sons," leapt forward to meet their end at the hands of an enraged demi-god. Meanwhile, Lorgar mirrored his brother Primarch's actions, and slaughtered enemy Astartes with contemptuous ease. Just as the Word Bearers struggled to stand before Corax, so too did the Raven Guard fall back and die in droves.

Suddenly, the Urizen halted his attack. He noticed that Corax was wading through the Gal Vorbak, ripping his daemon-possessed crimson warriors apart. Given a blessed respite from the Primarch’s murderous advance, the Raven Guard were falling back from him in a black tide. They left their dead in a carpet at the Primarch’s feet.

Despite the protestations of both Kor Phaeron and Erebus, Lorgar disregarded their counsel and sprinted forwards across the churned earth and dead bodies of his brother's Legion to engage in a battle he had no hope of winning. He saw his brother -- a man he had barely spoken to in two centuries of life, a man he barely knew -- butchering his sons in a vicious rage. There was no thought of conversion. No hope of bringing Corax into the fold, or enlightening him enough to cease this murderous rampage. Lorgar’s own anger rose to the fore, burning away the passionless killing of only moments before. As the Word Bearers Primarch hammered his way through the ranks of the dying Raven Guard to reach his brother, he felt power seethe within him, aching to rise out. Always before, Lorgar had bitten back his psychic potential, hiding it and hating it in equal measure. It was unreliable, erratic, unstable and painful. It was never the gift it seemed to be for Magnus the Red, and thus Lorgar had swallowed it back, walling it up behind unyielding resolve. No more. A scream of release tore itself free, not from his mouth, but his mind. It echoed across the battlefield. It echoed into the void. Energy sparked from his armour, and a sixth sense unrestrained at last, with its purity perhaps coloured by Chaos, exhaled from his core. Lorgar felt the heat of his own fury made manifest. He felt his unchained power reaching out, not only to enhance his physical form, but reaching to his sons across the battlefield. And there he stood at the heart of the killing fields, winged and haloed by amorphous contrails of psychic fire, shouting his brother’s name into the storm. Corax answered with a shriek of his own -- the call of the betrayer, the cry of the betrayed – and the raven met the Heretic in a clash of Crozius and Lightning Claw.

In response, the Gal Vobak underwent their final metamorphosis, changing into their true daemonic forms. Their ceramite armour had fused to flesh, layered by dense bone ridges and spines, as they sprouted all manner of razor sharp claws, talons and wings. They warped into new, bestial forms, marking them out as amongst the first of the Possessed. Meanwhile, the Primarchs fought in furious combat -- Corax fighting to kill, while Lorgar fought to stay alive. During their duel, Corax hurled insults and accusations at his former brother. He wanted to known why Lorgar and his Legion had committed such treachery. Lorgar shared with his brother the future visions he had seen of their father -- a bloodless corpse, enthroned upon a seat of gold and screaming into the void forever. Angered by his brother's lies, Corax lashed out furiously with his pair of Lightning Claws across Lorgar's face, cutting the meat of his cheeks deeply. Lorgar would bear those scars until the day he died.

The two Primarchs traded vicious blows, but the Raven Lord had the advantage not only speed and finesse, but of also being a penultimate warrior with decades of fighting experience. Lorgar did not, for he had always been more of a scholar than a warrior, and his lack of experience cost him dearly as Corax impaled Lorgar through his stomach, the tips of his metre-long talons glinting to the side of his spine as they thrust out his back. Such a blow meant little to a Primarch -- only when Corax heaved upwards did Lorgar stagger. The claws bit and cut, sawing through the Word Bearer’s body. The Crozius Illuminarum slipped from the impaled Primarch’s fists. Those same hands wrapped around Corax’s throat even as the Raven Lord was carving his brother in half. The Raven Lord remained untroubled by his weaker brother's grip. Lorgar crashed his forehead against Corax’s face, shattering his brother’s nose, but still he could not free himself. The Raven Lord gave no ground, even as a second, third and fourth head butt decimated his delicate features. The claws finally jerked, snagged against Lorgar’s enhanced bones. Corax tore them free, inflicting more damage than the first impaling had done. Blood hissed and popped as it evaporated on the force-fielded claw blades. Lorgar fell to his knees, hands clutched over the ruination of his stomach. As Corax stepped closer, he raised his one functioning claw to execute his brother. Lorgar screamed his defiance at Corax, lost in the irony that of all the sons of the Emperor, he was the one soul of the twenty Primarchs who had never wished to be a soldier. And now here he would die, at the heart of a battlefield. As the claw fell, it struck opposing metal.

Corax looked to meet eyes as black as his, in a face as pale as his own. His claw strained against a mirroring weapon, both sets of blades scraping as they ground against each other. One claw seeking to fall and kill, the other unyielding in its rising defence. Where the Raven Guard Primarch’s features were fierce with effort, the other face wore a grin. It was a smile both taut and mirthless -- a dead man’s smile, once his lips surrendered to rigor mortis. It was Konrad Curze, the Night Haunter and Primarch of the Night Lords. Corax sought to wrench his claw free, but Curze’s second gauntlet closed on his brother’s wrist, so that Corax would be unable to fly away and escape his fate. Curze looked upon his prostrate brother and ordered him to rise from his knees, disgusted at his cowardice. Corax was not idle as this exchange took place. He fired his flight pack, burning his fuel reserves to escape Curze's grip. The Raven Lord’s claw ripped free, and Corax soared skyward, carried on jet thrust away from Curze's rising laughter. Curze then shoved Lorgar back towards his Word Bearers.

Around them both, the grey Legion warred with the warriors in black. Lorgar thanked his brother for saving his life. But Curze warned him that he would let him die next time. Lorgar's bitter retort was halted as he took in the scene of the the transformed Gal Vorbak -- their armour was crimsom and ridged bone. Great claws, both metallic weapons and fleshy, jointed talons, extended from bestial arms. Every helm was horned and every faceplate was split by a daemon's skullish leer. Disgusted by this horrific sight, Curze turned his back on Lorgar and commented that he was so much more than merely foul, he was rancid with corruption.

Though grievously wounded, Lorgar would live. The Traitors had carried the day and dealt the Emperor and the Imperium a grievous blow. As the Horus Heresy began in earnest, Horus now possessed nine Space Marine Legions and had all but destroyed three of the remaining nine Loyalist Legions. The path to Terra was wide open, and the decisive Battle of Terra and the Siege of the Imperial Palace would follow after seven more years of blood and terror as the Traitor Legions penetrated to the very heart of the Imperium of Man.

The Harrowing
"Though the battle had ended and the enemy was far from the reach of our blades, most of us didn't come back from the Urgall Depression. Even those men who escaped, those pitiful few, even they didn't come back. They're still there now. We all are, fighting for our lives."

- Unknown Legionary survivor of the Istvaan V Massacre

Lesser troops would have given up and accepted their fate in the face of such overwhelming opposition, but the warriors of the Salamanders and Raven Guard were Astartes. So they fought like never before, knowing their doom was at hand, and desiring to make the Traitors pay in blood for every one of their number that fell. Caught between two armies, the first wave of the Loyalist forces was systematically massacred. Unrelenting gunfire from the Iron Warriors at the drop site, and the resurgent forces along the Urgall Depression crushed the Salamanders and Raven Guard in a terrifying vice, and cut them to pieces in a murderous storm of fire and blood. Warriors of the Alpha Legion and Word Bearers followed their leaders onto the black plains of Istvaan V, their guns blazing and their Chainswords bright as they cast off the last remnants of their loyalty to the Emperor and turned their weapons on their brothers. The Dies Irae killed scores with every shot of its mighty weaponry, striding like a giant daemon of legend through the benighted slaughter. White-hot fire blossomed amongst the Loyalists and killing flames sawed across the black desert, vaporising men and turning sand to glass. Traitor tanks roared from the Urgall Hills, weapons blazing and crashing the wounded beneath their tracks.

Refusing to surrender, the remaining Raven Guard and Salamanders Astartes stubbornly defended themselves, trying to hold off the inevitable slaughter for as long as possible. Though they suffered an atrocious number of casualties, the Loyalists managed to hold their own, until the Primarchs Mortarion of the Death Guard and Angron of the World Eaters joined the fray. Bolstered by the support of the infamous Imperator-class Titan Dies Irae, the Traitors killed tens of thousands of Loyalist Astartes. At the height of the massacre, with victory in his grasp, the Warmaster took to the field of battle, surrounded by Captain Falkus Kibre and his Justaerin Terminators. The remnants of Horus' Mournival fought alongside him, the Warmaster's magnificent black armour and amber chest adornment gleaming bloody in the firelight. The killing fields of Isstvan V ran red with the blood of the Loyalists, their brave attempt to halt the rebellion of Horus now rendered little more than ragged flesh and blood that fought for the last shreds of honour left to them. Any hope for escape for the Loyalists was quickly crushed when the traitorous Iron Warriors destroyed the first wave's drop ships. The Loyalist starships still orbiting the embattled planet were also largely annihilated by the vastly superior numbers of the Traitor fleet after the second wave's warships turned their guns upon the vessels of the true Loyalists. Despite the odds arrayed against them, some of the Loyalists on the ground managed to survive -- they miraculously escaped through the tightening cordon of Traitors that surrounded their position. The Raven Guard fared better than the Salamanders in escaping the brutal massacre. But the Salamanders managed to assist a few surviving Astartes from the decimated Iron Hands Legion to also escape the slaughter. As for Vulkan, he and his Salamanders had at last been driven together to fight a desperate, final stand and were perhaps the last to fall, encircled by a thousand foes and ungulfed in a cataclysm of firepower. Imperial history does not record the ultimate fate of these surviving Salamanders or their missing Primarch Vulkan. The Alpha Legion were the first to fall back from the slaughter, their deed one, their objectives claimed. After, it is said, the Sons of the Hydra withdrew in whispered order, and in perfect stillness watched the last act of murderous despoil unfold as the guns of the Iron Warriors at last fell silent and the rest took their fill of trophy taking, dark ritual and madness unfettered. The grievously wounded Raven Guard's Primarch just barely managed to board a fleeing Thunderhawk gunship to make good his escape, but was thwarted in the attempt when it was shot down almost immediately by the gunfire of the Traitors. The badly damaged ship crashed on the outskirts of the Urgall Plateau.

On the black sands of Istvaan V more than 200,000 Space Marines lay dead, a Primarch had been slain and two others were missing, presumed dead, their Legions all but wiped out. With them died the Emperor's own dream of dominion of the stars.

Warmaster Triumphant
"The road to Terra is open. The time has come for us to take the war to the Emperor in his most impregnable fastness! We will make immediate preparation for the invasion of Terra and an assault on the Imperial Palace. Make no mistake, and it will be ours, my brothers! This will be no easy task, for the Emperor and his deluded followers will fight hard to prevent us from interfering with his plans for godhood. Doubtless much blood has yet to be spilled, theirs and our own, but the prize is the galaxy itself...Are you with me?"

- Warmaster Horus, Master of Istvaan

After the killing had stopped and the dead were gathered into great funeral pyres across the broken desert of the Urgall Depression, the once-grey skies of the planet burned orange with the reflected glow of a thousand pyres. The firelight bathed the rippling, glassy sands in a warm radiance, and towering pillars of black smoke from the burning corpses filled the air. Thousands of Astartes loyal to Horus gathered before a great reviewing stand, constructed by the Tech-priests of the Dark Mechanicus with astonishing speed. As the sun began to sink beyond the horizon, the smooth black planes of the stand shone with a blood red glow. The stand was erected as a series of cylinders of ever decreasing diameter, one standing atop another. The base was perhaps a thousand metres in width, constructed as a great grandstand upon which the Sons of Horus stood, their pre-eminent position as the elite of the Warmaster in no doubt after this great victory. Each warrior bore a flaming brand, and the firelight cast brilliant reflections from their armour.

Atop this pedestal of flame was another platform, occupied by the senior officers of the XVI Legion. Above the senior officers of the Sons of Horus stood the Traitor Primarchs. The sheer magnificence of such a gathering of might was breathtaking. Seven beings of monumental power stood on the penultimate tier of the reviewing stand, their armour still stained with the blood of their foes, their cloaks billowing in the winds that swept the Urgall Depression. Finally, the uppermost tier of the reviewing stand was a tall cylinder of crimson that stood a hundred metres above the Primarchs. Horus stood on top of it, his clawed gauntlets raised in salute. A furred cloak of some great beast hung from his shoulders, and the light of the corpse pyres reflected from the amber eye upon his breastplate. The Warmaster was illuminated from below by a hidden light source, bathing him in a red glow that gave him the appearance of the statue of a legendary hero, as he stood looking down on the endless sea of his followers from the towering platform. As the sun finally dipped below the horizon, a flight of assault craft roared over the Urgall Hills, their wings dipping in salute to the mighty warrior below. Solid waves of cheering crashed against the reviewing stand, howls of adulation torn from tens of thousands of throats. No sooner had the aircraft passed overhead than the massed Astartes began to march around the reviewing stand, their arms snapping out and hammering their breastplates in salute of the Warmaster. At some unseen signal a flame ignited on the northern slopes of the Urgall Depression and a blazing line of phosphor leapt across the ground in a snaking arc that described the outline of an enormous blazing eye upon the hillside. The adulation soared to new heights as the Eye of Horus seared itself into the sands of Isstvan V, the Warmaster’s forces roaring themselves hoarse in his praise. Super-heavy tanks fired in salute of Horus, and the towering immensity of the Dies Irae inclined its massive head in a gesture of respect. The ashes of the dead fell like confetti over Horus' mighty army as thousands of Traitor Astartes cheered, their cries of "Hail Horus! Hail Horus!" resounding long into the darkness.

Total Victory Denied
"The hero has for his tomb the galaxy entire."

- From the Memoriam Handbook of the Imperial Army, by the hand of the Iterator Khar'rhy Rakal

As crushing as the Traitor victory at the Dropsite Massacre had been, it quickly became apparent that it was not total. A number of small groups of survivors had managed to break out of the encircling trap as soon as it became clear that all was lost, either managing to escape via gunship in the chaos or slip away into the crags and shifting volcanic sands and dust storms of the desert plains; an escape aided in part by the bloodlust of some of the Traitors, and the eagerness to pick over the spoils of battle by others, contempt the renegade Legions seemed to hold for each other, even then. In the skies above Istvaan V, the war fleets of the Loyalists had also been betrayed and assaulted and here, although overmatched, the battle had not been such a one-sided affair as the Traitors would have liked. The Loyalist vessels fully void shielded and on battle alert as befitted them in a war zone, were quick to respond in kind once the initial assault had been weathered, with many of their number damaged, but fare from destroyed by the sudden attack of their supposed allies. The resulting void battle had lasted for many more hours than the carnage on the ground, and some Loyalist warships had fought on stubbornly, refusing to abandon their Legion planet-side to whatever dark fate had befallen them and paid the ultimate price for their loyalty. Others, badly damaged, were either driven off, or realising the futility of the overwhelming odds they faced as the fleets of the first Traitor Legions re-appeared succeeded in escaping the system, the hounds of the enemy at their heels and bitter vengeance in their hearts.

The Battle of Istvaan V was over, the treacherous Warmaster was its victor. The whirlwind of galactic war had been sown, and the dark gods would reap the years of terror and bloodshed that would follow.

The Night of Butchery
All that remained on the first night of Istvaan V is scattering and fragmentary accounts, many of them entirely contradictory. Some survivors spoke of tides of Traitors surging across the hills in a berserk frenzy, howling for the blood of the survivors. Others described a deep, sonorous chanting that rolled through the valleys like thunder and stirred the dread in the hearts of those still loyal to the Emperor. Still other evidence shows bands of Traitors descending on isolated Loyalists and tearing them apart in an atavistic savagery, while circling gunships loosed fire indiscriminately, little caring of who they slew so long as it was not their own. How many battles raged throughout that night cannot be known, for every Legionary fought his own bitter war for survival. Even as the main body of the foe harried the Raven Guard from behind, others fell upon them from above as they passed along cracked ravines. Few Legionaries had any ammunition to spare, and so most of these battles were fought with fists and combat knives. When individual Raven Guard fell, their brothers made impossibly valiant attempts to rescue them from the howling, blood-maddened foes. Those who could walk bore those who could not, the withdrawal ever teetering on the edge of being overrun. But by the time the wan light of Istvaan V's sun appeared on the horizon, barely penetrating the tortured, smoke-stained skies, the bulk of the surviving Raven Guard had broken free of their pursuers, finding sanctuary in the maze-like ravines beyond the Urgall Hills, for a brief moment at least.

As the Raven Guard were fighting alongside their Primarch, those Legionaries unable to escape the noose of the Traitor armies were being systematically butchered. As the tides of war receded, the Traitors stalked the battlefield, knee deep in the shattered bodies of their erstwhile kinsmen, seeking the dying that they might deliver death. Others sought the wounded in order to perform abominable tortures upon their already ruined flesh. Some Traitor Legions piled their own dead on to great pyres so that their deaths might be honoured as the growing flames licked the blackened skies. The World Eaters are known to have performed one of the bases acts of savagery that day by butchering the dead and dying, decapitating them, flensing the flesh from their skulls and piling these in massive ossuary-cairnes. The Word Bearers, following the teachings of their damned Primarch, enacted their own victory rituals, the terrible significance of which is now all too well known to the Imperium. As if to heap infamy upon ignominy, the Traitors began another, still worse mutilation of the fallen. Tens of thousands of corpses had their Progenoid Glands -- the implant that bears the Space Marines' gene-seed by which the Legions themselves are propagated -- torn bloodily form them, for what fell purpose few would dare speculate.

Ravens' Flight
With hordes of Traitors closing in on the now isolated Raven Lord and a storm of fire scything through the air, a single Raven Guard Thunderhawk, the Umbra Secundus, commandeered by Master of Descent Alvarex Maun, successfully descended from the fire-streaked skies against the odds, and blasted a landing zone nearby the Primarch. Having boarded, Corax remained at the open assault ramp, and it is said his black eyes burned as he cursed the numberless hosts even as the gunship rose once more, the backblast of its rocket engines making a pyre for the betrayed dead that had fought to the last alongside their lord. Inevitably, the sheer weight of fire directed at the Thunderahwk shredded its armoured skin, tore one wing off and ripped its cockpit canopy wide open, slaying both pilot and co-pilot in an instant. Wrestling with the ruined controls even as the cockpit burned around him, Strike Captain Maun fought to arrest the sticken gunship's terminal descent, turning what would have been a catastrophic crash into a controlled landing. Though most of the crew were slain and the Strike Captain badly wounded, the Primarch survived thanks to Alvarex Maun's dedication and sacrifice, the two rejoining the Legion as the sun finally set on that great day of betrayal.

Even as the Raven Guard slipped their howling pursuers, yet another torment was visited upon the war-shattered surface of Istvaan V. The flaming hulks of those Loyalist war ships caught in the Traitors' ambush now began their inexorable and fatal descent. Soon the first large fragments of wreckage speared downwards, and smashed into the ground with a force equal to a planetary bombardment. The resulting explosion scoured a crater a hundred metres across and sent up a mushroom cloud tens of thousands of metres into the atmosphere. Moments later, searing debris rained down and a wave front of ashen smoke smothered all. It would be the first of many hundreds of impacts that would fall upon the embattled planet's surface over the coming days, weeks and months, wreaking indiscriminate destruction upon Loyalists and Traitor alike. With the wreckage falling from orbit overwhelming the vox-net with impenetrable interference and the choking debris drastically curtailing visibility, the Raven Guard pressed ever deeper into the cracked land beyond the Urgall Hills, a vast, broken region called the Illium Rifts. By dusk on that second day, little definite had been learned of the fate of the Iron Hands and the Salamanders, and so Corax was seen to pace the outer limits of the rifts, his gaze dark, his humours swinging violently between choler and melancholy. Several times he led his chosen warriors out into the hills in search of his lost Raven Guard sons, and any other Loyalist force who might survive yet. Several times he returned with Raven Guard Legionaries, having come upon them in the hills.

Signs of other survivors having broken free of the massacre at the Urgall Depression were found all about, many in the form of tracks terminating in the broken corpses of once proud warriors run to ground like cornered animals. Throughout the night, still more scattered bands of Raven Guard staggered into the refuge, many wounded almost beyond the ability to fight, in body and in mind. Of all the horrors they had witnessed, of all the hurts they had withstood during the wars of the Great Crusade, here was an entirely new phenomenon. The betrayal that had split the Legiones Astartes in twain had inflicted upon them a wound no other foe had ever struck -- for the first time in the experience of any present, the vautned spirit, wrought by the hand of the Emepror Himself, was stretched unto the breaking point.

Under the unheeded gaze of the vigilant Raven Guard, the Traitor's intent unfurled. Ultra-heavy transport barques descended from the still-churning skis. The heaviest were large enough to embark the mighty Traitor Titans, while hundreds more would ferry the bulk of the Traitor Legions' line units into orbit and away to the next phase of the Warmaster's betrayal. Far-ranging Raven Guard reconnaissance squads reported to the Raven Lord that the bulk of each turncoat Legion appeared to be departing, but that each appeared to be leaving behind it a core of warriors, to what ends they could not determine. The only Legion not taking leave was the World Eaters, who's Traitor death squads ranged the hills and the wastes beyond, ever seeking to run more survivors to ground and to add more flensed skulls to the growing ossuary-cairns. Angron, it seemed, would not depart Istvaan V until the slaughter was complete. Confronted with the stark reality of the strategic situation, the Raven Guard fell back upon their instilled battle doctrines. Corax instigated a cunningly conceived series of diversionary attacks that drew Traitor hunters away from the gorges of the Illium Rifts in which the Raven Guard had taken refuge and led them away into the mountains and deserts north and south of the Urgall Depression. Raven Guard squads ranged far and wide in the course of these actions, sometimes returning with more survivors, more often with fresh wounds and fell accounts of the sights they had seen. The Traitor death squads were hunting down survivors as if engaging in sport, and enacting unspeakable tortures upon the bodies of those they ran to ground.

Many Loyalist survivors began to display signs of a psychotic break, turning upon their own brothers in with unreasoning savagery. Soon enough, the phenomenon was repeated. A number of Legionaries who had once serve din the Librarius approached the Raven Lord with their suspicions. Even without consciously engaging their psychic skills, each had detected a slow but inexorable build-up of psionic pressure. At first, they had taken the effect for a manifestation of so much violent choler unleashed in such a concentrated period and location during the Dropsite Massacre. Yet, as the days wore on, it had become increasingly apparent that something far darker and contrary to reason was occurring. It was the work of the World Eaters, and represented yet another sign of just how fare the Traitors had fallen.

All across the Urgall Depression and beyond, the World Eaters were raising ever taller pyramids of flensed skulls. At first they appeared random in form and function, though redolent of the death-fanes and ossuary-temples cast down on the most savage of human worlds during the Great Crusade. The act of gathering the skulls of the fallen, flensing them and piling them into vast pyramids all across the Urgall Depression and even further into the hills was revealed as some form of rite of victory. Somehow, this rite was proving to be the source of the madness that had afflicted the rescued Raven Guard and many others who tarried overlong in the shadow of the monuments. Some manner of psychic resonance was pulsing outwards from the vile monuments, filling those it touched with anger and bloodlust. Later on, Raven Guard reconnaissance squad would witness their erstwhile allies performing savage victory rituals about the monuments, confirming to many that the sons of Angron remained at heart no more than bloodthirsty primitives. Others saw in the rituals something far darker still, something spawned long ago in the darkness of Old Night.

It would be several years until the true nature of the phenomenon was revealed, their Pirmarch may have known more, the Raven Guard being blissfully ignorant of such things at that time, though even then it was obvious that some agency beyond the natural order of reality was abroad. Keeping his own counsel on the matter, the Primarch ordered a series of attacks against a small, select number of these vile structures, strike forces of chosen warriors planting Melta Bombs at their bases. The resulting detonations brought the targets crashing down in cleansing flames, the fell effect they exerted on the surrounding regions lessened, though it never entirely relented.

Consolidation
As the battles wore on, the Primarch reorganised his Leigon, forging it anew into something resembling less the brutalised victims of the Warmaster's betrayal and more a band of warriors determined to survive, or to sell their lives dearly in the attempt. Raven Guard strike forces launched a series of cautious, yet bold attacks against Traitor death squads isolated from the greater mass of the enemy, numerous small but bitterly fought battles out in the wastes. Many of these confrontations were fought with combat knives and improvised weapons; the objective to slay the foe and carry away what supplies could be salvaged from their bodies. In time, ammunition stocks were replenished to such a degree that more overt assaults could be launched, and it was as small groups of Raven Guard pushed ever deeper into the Traitor-haunted lands about the Urgall Depression that a grim discovery indeed was made.

Along the crest of the Urgall Depression, hundreds, perhaps even thousands of iron spikes and columns were found, driven into the black volcanic ground. Atop each was mounted the body, or body part, of a Loyalist Space Marine. Most had been executed while others lived on still, the superhuman physiology of the Legiones Astartes holding death at bay despite being eviscerated, impaled, dismembered and exsanguinated or having a hundred other, equally cruel and darkly invented injuries inflicted upon them. It was to the eyes of the Loyalist onlookers as if some plague of insanity had spread from their former brothers; that alongside treachery as terrible as it was, something of horror and madness unlooked for and inhuman had taken root. Here was the fate that the Traitors would inflict upon every Loyalist not slain in the cauldron of the Dropsite Massacre. Here, the Raven Guard recognised, was the fate the Warmaster would visit upon all those who refused to bow before him, even should every human world drown in blood.

In the east, Raven Guard scouts came upon a vast and hidden underground complex akin to the alien ruins which the Traitors had used as their dread fastness. With this discovery the Raven Guard had their sanctuary, and operations to relocate began within hours. The move could not have been more propitiously times, for as the last of the Raven Guard moved out, the night skies far to the west filled with the fires of massed retro jets. A vast flotilla of vessels was landing in the calderas of the extinct volcanoes over the western horizon, a flotilla belonging to the Warmater's Traitor Mechanicum allies.

Reclamation
From the cavernous holds of the gargantuan Mechanicum vessels marched a cohorts of traitor Mechanicum tech-helots, and thousands upon thousands of Servitors and tech-thralls were driven forth towards the wreckage-strewn Urgall Depressioin. The Warmaster's renegade Tech-priests were beginning a reclamation operation of staggering scale, one that would grant the Warmaster an immediate advantage in supply and matériel. The entire depression was strewn with equipment of incredible military worth -- even those vehicles and other items damaged beyond repair still of enormous value as salvage. The wrecks of hundreds of super-heavy tanks still smouldered there, while the toppled forms of once mighty Titans were testament to the sheer destruction unleashed in the few hours of the Dropsite Massacre. The ground was carpeted with the remains of hundreds of thousands of Space Marines, each of whom still bore full Legiones Astartes battle plate and carried weapons and other items of equipment representing the very pinnacle of human technological achievement. Within hours, the flickering glow of plasma cutters was to be seen all across the depression as reclamation parties began their grim harvest. The operation would continue for many weeks, pushing outwards across the depression until, at lenght, only the worthless detritus of war remained.

Even weeks after the Dropsite Massacre, still-living bodies would be discovered in amongst the thousands of dead, the gene-enhanced physiology of the Legiones Astartes able to enter a state of suspended animation in which the body might heal from the most horrendous wounds in time. Some Traitors, most notably elements of the Word Bearers and Emperor's Children -- in whom it seemed the dark madness of nightmare had truly awakened, but whose true cause was not yet suspected by outsiders -- took cruel delight when these were discovered; sometimes administering alchemical preparations to awaken them, only to torture and execute the unfortunate victims, exacting upon them what amounted to a second death. The sons of the Raven did what they could to disrupt the work of these reclamation parties, even while seeking to avoid their own capture and tortuous end. Dozens of Tech-Priest overseers fell; victim to the silenced sniper rounds of Legion Seekers determined to exact vengeance for the dark crimes witnessed through their targetting scopes, or found explosives booby-trapped to their would-be prizes of salvage. But ultimately, such counter-attacks were mere pin pricks to the vast scavenging effort the Traitors had undertaken.

The Hunters
Around the twentieth day after the Dropsite Massacre, the Legion's fight for survival entered a new and bitter phase. By this point, the Traitors were aware that a significant force of Loyalists survived yet and had made a number of attempts to bring them to battle. Lord Corax, however, was not to be drawn into an open confrontation his forces had no chance of winning. Instead, he executed a series of strike designed to divert and disrupt the enemy's operations and challenge their domination of the wastes surrounding the Urgall Depression. The greater number of Traitors left behind to scour the world belonged to the World Eaters Legion, led by their savage Primarch Angron. Despite the Loyalists' actions, the World Eaters rarely split their forces, instead scouring the depression and the wastes beyond in a vast and ravaging mass, their war cries audible for many kilometres all about. The other, smaller, Traitor Legion contingents deployed differently, however, leading the Raven Guard to the conclusion that those left behind on Istvaan V were some sort of punishment detail or else represented elements of the Traitor Legions their Primarch had decided to keep apart form the bulk of their forces. This hypothesis was further evidenced as a number of these remaining Traitor contingents were revealed to be factious and ill-disciplined, the glory and nobility of the Emperor's Great Crusade apparently forgotten to them. The Sons of Horus were often encountered in small bands of hunters, most accompanied by cyber-mastiffs able to detect the proximity of even the stealthiest of Raven Guard warriors and to track them across many kilometres. The Word Bearers by comparison followed their own unknowable ritualistic dogma and often staying clear even of their own supposed allies -- perhaps because these actions would have prompted too many questions they would prefer not to answer of their "brother-in-arms". The Iron Warriors contingent, smaller but well provided for in terms of heavy vehicles and war machinery, scoured the wastes in compact armoured columns, the largest three of which presented Corax with the opportunity he had been seeking.

The Raven Lord's campaign against the Iron Warriors amroured columns was to space several weeks and heralded some of the most intense fighting prior to the very final battles on Istvaan V. After many weeks of gathering vital intelligence, Corax mustered his forces north of the Urgall Depression and sprung an ambush against the smallest of the three Iron Warriors armoured columns. After striking the surprised Traitors, they quickly withdrew, leaving behind the corpse of several hundred Traitors and guttering hulks of dozens of vehicles. Though this battle paled into insignificance compared to the losses the Traitors had inflicted upon the Loyalsits at the Dropsite Massacre and afterwards, in terms of morale, however, it could not have been more important. The Raven Guard had struck a meaningful blow against the Traitors, and even if every son of Corax eventually died on the blasted surface of Istvaan V, they would do so vindicated and with honour. As Corax and several of the Mor Deythan watched the rear as the main body withdrew, they witnessed a phalanx of walkers -- their form unfamiliar but clearly the product of some esoteric discipline practised by the Warmaster's Traitor Mechanicum allies. This was the first recorded sighting of the war engines that would come to be known as the "blind-hunters", a class of mechanical automaton possessed of a dark intelligence and a fearsome array of weaponry, and intended to hunt down every last survivor left upon the surface of Istvaan V. Their very existence and presence on the planet at that juncture was further evidence of the staggering scope and scale of the Warmaster's treachery.

The Fallen Crusader
The Raven Guard had but days to consolidate after their victory before another Iron Warriors armoured column was reported pressing eastwards across the wastes, winding its way into the twisting ravines of the Illium Rifts. Lord Corax ordered an immediate and overwhelming attack. The battle that ensued took place in the abyssal darkness of the ravines and was as bitterly fought as any boarding action or hive scouring the Legion had ever undertaken. The Primarch was ever to be found at the heart of the fight, while the Jump Pack-equipped units made wide outflanking manoeuvres so that the Iron Warriors were cut off, attacked from multiple directions with no hope of retreat. The Iron Warriors gave not an inch even as their dead choked the gullies. Though less than a hundred Iron Warriors remained they were bolstered by a dozen Dreadnoughts of varying patterns. From the Loyalists' midst strode the Raven Lord, as he faced off against a Contemptor Pattern Dreadnought in close-quarters combat. A single word passed between them, the Primarch speaking the name of the Iron Warriors veteran within the Contemptor, evidence that the two must have fought alongside one another during the Great Crusade. This curse spoken, the two squared off against one another in the manner of pit fighters preparing to fight to the death. Quickly leaping onto the Dreadnought's back, the Raven Lord made short work of it as he tore into the Contemptor's ceramite armoured shell and pulled out the armoued brain case and trailing spinal column of the veteran Iron Warrior Legionary who had been interred within the sarcophagus. A moment later, the Contemptor's systems disengaged and the once-mighty war engine collapsed, the Primarch leaping clear before it hit the ground. This was the signal to attack.

In the ensuing conflict the Raven Guard leapt from the dark to fall upon the beleaguered Iron Warriors, the Primarch engaging several more Dreadnoughts as his assault squads cut into the enemy Legionaries. Not a single Iron Warriors Legionary was allowed to escape, and in truth none attempted to do so, each fighting until the bitter end. Eventually, silenced descended upon the scene, the rocky floor of the crater carpeted in the broken bodies of over a hundred Iron Warriors and not a small number of Raven Guard. In amongst the wreckage were the ruined, smoking hulks of a dozen Dreadnoughts, the remains of once-mighty heroes interred within cast to the bloody ground by the vengeful Primarch of the Raven Guard. His contempt for the scope of their fall from grace writ across his grim visage. With a nod, the Raven Lord gave the signal for his forces to withdraw, the dead left in their wake as a powerful message to the Traitors. It would not be the last of its kind.

Into the Rifts
As the shadows of resistance and search, hard-fought ambush and flight wore on, the presence of increased numbers of Word Bearers within the Illium Rifts made it apparent that the Traitors were pushing their hunt for survivors ever further outwards, once again threatening the safety of the Legion's sanctuary. Steps were taken to move the Legion's wounded, as well as its meagre stores and limited command facilities ever deeper into the mighty chain of caverns beneath the rifts. The further the Raven Guard pressed into the stygian darkness, the more apparent the aline nature of the tunnels became. The material that the cavern's walls were comprised of appeared to have a deadening effect on a wide band of electromagnetic radiation. Furthermore, the construction seemed to be exerting an influence on the psionic level too, serving to nullify or shroud psychic effects. This may have contributed to the Traitors' inability to locate the Loyalists' refuge using technological or psionic means, but many claim it must have done so, for the Traitors scoured the lands above but never discovered it using these methods, despite passing within metres of the entrances on several occasions. One particular groups was not searching using any subtle or esoteric methods. The third Iron Warriors armoured column forged eastwards, crushing all it encountered in its ceaseless hunt. Set on a course that would take them directly past a number of the hidden entrances to the refuge, it was judged a certainty that the Iron Warriors might discover, by dogged search or blind chance, what they fellow Traitors had failed to locate by more subtle means. Faced with the likelihood of imminent discovery, the Raven Lord mustered all available warriors and committed themselves to a daring assault, sweeping in upon the Traitors with hatred welling in their hearts. The Iron Warriors responded with implacable ferocity bit were soon engaged in a bitter, gruelling contest from which only one side would emerge. Even as his sons fought on, mired in the blood of friend and foe alike, the Raven Lord plunged into the cauldron of war alone, his single Lightning Claw lashing out in great, thirsty sweeps. The third and final portion of the Iron Warriors Legion left behind to scour Istvaan V of Loyalists was utterly destroyed, and while others of their kin remained in the Urgall Hilss manning their fortifications, as a coherent force of aggression the sons of Perturabo were spent. As the Raven Guard marched wearily back towards their sanctuary in silence, the harrowing-horns of the Traitor Mechanicum's blind-hunters echoes out across the cracked wastes, and black storm clouds gathered in the grey skies overhead. At the last, the clouds broke and black-tainted rain fell upon the blood-crusted surface of Istvaan V.

The Raven Lord Alone
"We have no room for hope. We plan and we act. Hope is for dreamers and poets. We have our will and our weapons, and we shall dictate our own fate."

- Lord Corax, Primarch of the Legio Astartes Raven Guard

As the black rains lashed the wastes it enforced a temporary cessation of hostilities, the Traitors pulling back from their grim hunt and the Raven Guard taking the opportunity to consolidate in their sanctuary. For several days, the Legion's officers reconstituted and reorganised while the Apothecaries tended to wounds long neglected in the midst of constant war. At the height of the rains, Lord Corax once again took his leave into the rain-blasted gullies without a word of explanation. Those Legionaries who knew their Primarch of old counselled the other to fret not, for it was well within the Raven Lord's demeanour to act alone in such circumstances, utilising his unique Emperor-gifted abilities to pass unseen where few others could. History does not record where the dark-eyes Primarch walked, not what grim sights he bore witness to during the day and night he went alone across the wastes. Fragmentary accounts compiled much later based on his conversations with Rogal Dorn hint that Corax penetrated deep into Traitor-held territory, perhaps even treading the corpse-carpeted Urgall Depression itself. When at last the Primarch returned, he convened a council of his most trusted senior commanders and while the words that passed between them go unrecorded, the Primarch's intent remains unequivocal. The Raven Guard must survive, he ordained. Not simply to preserve the Imperium's might, although that must surely have been a consideration. Rather, while but a single Raven Guard continued to fight, no Traitor could rest without fear that justice would be visited upon him.

The Sundered Legion
Records show that in the aftermath of the long contaminated rainfall, a dense, stinging fog reeking of chemical-rich blood rose from the broken ground to blanket hundreds of square kilometres. This all-pervading taint of death, which can be said perhaps in retrospect to have some Warp taint infecting it thanks to the Word Bearers Legion's dark ministrations, took its toll on many of the Raven Guard, stretching the sanity of many even further towards breaking point. As Legiones Astartes, not a single Space Marine would surrender to cowardice or weakness of will, yet the apocalyptic slaughter and the cumulative effect of weeks of fighting, combined with little or no rest or sustenance and the need to wreak bloody vengeance upon the heads of Traitors caused many to descend into a twilight existence somewhere between exhaustion and rage, denial and defection. Under such relentless pressure, even a Space Marine takes on a haggard caste, the already pale, hollow-eyed Raven Guard coming to appear as armoured vagabonds, their battle plate a haphazard amalgamation of replacement parts scavenged from the dead of any and all Legions present on Istvaan V.

At some point around the fortieth day after the Dropsite Massacre, a large force of Word Bearers, under the command of the war-leader Elexis, penetrated the ravines to the north of the Raven Guard Legion's sanctuary. Elexis had discerned that the Raven Guard forces he had encountered earlier were a part of a far larger force, and he was determined to claim their heads for himself. It is noteworthy that Elexis appears to have withheld his suspicions from other Traitor factions, in particular the World Eaters, whose Primarch Angron still scoured the far wastes in search of one or both of his lost brothers. Had he done so, there is little doubt the Traitors' assault would have been a direct and brutal one, far from the cunning infiltration from an unanticipated quarter that was in the event launched.

On this occasion, the Raven Guard did not launch an all-out attack to repel the infiltration. Instead, the Word Bearers were allowed to penetrate many kilometres into the ravines and the twisting gullies while the Raven Guard watched on from the shadows, allowing the Word Bearers to pass by as other units feigned retreat in the face of the Traitors' advance. Eventually, the trap was set and the Raven Guard launched their ambushe. At a stroke, dozens of separate Word Bearers units were engaged, none of them able to lend aid to their brothers. The aim of the ambush was twofold: in addition to cutting down hundreds of the hated foe, the Raven Guard were able to capture several of the Traitors, though all but one were able to take their own lives before they could be subdued. The sole remaining Traitor was brought before Lord Corax, a circle of Raven Guard forming about the base of the ancient crater where the Traitor was cast as the skies of unnatural lightning and the black rains came down once more. None would dare speak of the manner in which the Primarch and his officers questioned the Traitor, nor of the nature of the death he was afforded at the last.

Soon after though, a stream of orders were disseminated through the Legion and from these certain facts have been pieced together. It was confirmed that Angron was the only Traitor Primarch who had remained on Istvaan V and that his World Eaters represented the only Legion still deployed in full strength, the remainder having left behind only limited contingents to hunt down the last remaining Loyalists. Perhaps the most vital information extracted from the Traitor was that Angron was aware that Corax yet lived, and was itent upon scouring the entire Illium Rift in order to bring him to battle. A massive assault was being prepared, one that the Word Bearers commander Elexis had attempted to pre-empt for his own glory, and failed. Forewarned of the imminent attack, the Raven Guard made immediate preparations to relocate once more. Some amongst their ranks spoke out against retreating in the face of the enemy, advocating to make a defiant last stand. The line officers quelled such opinions the instant they were voiced, but it was inevitable that the Legion's upper echelon officers and the Primarch himself should hear of them. When this happened, the reaction was curt and uncompromising. The Raven Guard would live and die at the word of the Primarch alone. If the end was to come, it would be at a time and place of his choosing, and none other.

The evacuation of the sanctuary could not have been timed more fortuitously, for even as the Raven Guard's rearguard units cast a final glance westwards over their shoulders, they spied its demise. A cohort of blind-hunters was closing in on the hidden main entrance, the baleful dirge of their harrowing-horns blasting out across the wastes. In the wake of the fell war machines came a great mass of Legiones Astartes, the white and blue livery of the World Eaters easily visible against the grey sky and black ground. At the last, Corax himself joined the rearguard and watched silently as the land was swallowed in a mass of explosions, the savage sons of Angron setting the region aflame in their anger at having discovered their prey had escaped them yet again.

The Final Days
In the aftermath of the evacuation of the sanctuary, the Raven Guard Legion's fight for survival and vengeance entered a final, desperate phase. Where before the Legion had been able to exert some control over their fate, albeit one that could not be maintained forever, now they were the victims of circumstance once more. The Raven Guard numbered even fewer warriors than they had in the immediate aftermath of the Dropsite Massacre, eighty days and more of continuous battle and hardship having claimed hundreds more. Many of the most severely wounded Legionares evacuated from the sanctuary had taken their own lives so that their brethren might not be burdened by them, despite the efforts and protestations of their kin. With this a deep melancholy settled upon the Raven Guard, who had never been an ebullient kindred even at the height of victory. Individual Legionaries became sullen and withdrawn as a grim acceptance of the inevitable took hold. Though the Raven Guard Legion fought on against any and all Traitors it encountered, many fought because the only alternative was to die, not because they cleaved to any hope of eventual victory.

The fighting was continuous. The only difference was that now the Legion had no refuge other than the twisting ravines of the Illium Rifts, and it soon became apparent that there was scant chance of locating another refuge, for the World Eaters and the Mechanicum's blind-hunters were relentless in their efforts to bring the Raven Guard to battle. Though they remained one step ahead, the Raven Guard were rarely afforded the time needed to properly reconnoitre the path ahead or to formulate a strategy to counter the Traitors' incessant attacks. Try as they might, the Raven Guard could not wrest the initiative from the Traitors, a situation entirely anathema to them. Step by step, the Raven Guard were pressed ever eastwards. Inevitably, they would eventually be driven into the trackless, inhospitable Gular Salt Plains, an uncharted land even the superhuman physiology of the Legiones Astartes could not withstand over-long.

The Beginning of the End
As the battles raged, the western skies flickered star white as the Traitor Mechanicum incinerated the regions they had cleared of salvageable matériel. Grim faced, the Raven Guard could only fight on as the destruction spread ever outwards from the Urgall Depression, breaking like a wave over the Urgall Hills and spewing kilometre after kilometre across the wastes and into the Illium Rifts beyond. For long days and nights, the Raven Guard fought on in this manner, selling their lives dearly as the wastes echoes with the sound of Angron bellowing for his brother to face him. The salt plains grew ever closer to the east as the raging fires consuming the western skies crept ever onwards. Though they Raven Guard fought on, they were by now outnumbered ten to one and had no hope of reinforcement or resupply. With the inexorable march of the Mechanicum's land-razing firestorms, all hope of finding any other survivors or of locating any fresh source of ammunition was fled and now they were being channelled into an ever narrower field of flight by the massed firepower of the Whirlwind and Scorpius tanks of the World Eaters had deployed to the flanks of their advance, bracketing all avenues of escape with withering fusillades of missile fire. Yet still, the Raven Lord did not order his Legion to turn and face its pursuers and make the last stand all knew must surely come, and soon. The Raven Lord kept his own silent council, and none dared raise a word of objection.

Sunrise, such as it was upon the tainted, fog-shrouded surface of Istvaan V, on the ninety-eight day after the Dropsite Massacre saw the last three thousand Legionaries of the Raven Guard mount the crest of the final rise and look upon the endless expanse of the Gular Salt Plains. The air was thick with toxins rolling in from the crusted plains and the black contrails of whirlwind fire, the eerie howl of the tortured winds almost loud enough to drown out the bass roar of the tens of thousands of World Eaters charging across the broken land. The Raven Guard survivors were finally backed into a literal corner. Now at last, the Raven Lord ordered his sons to halt. Backs to the Gular Salt Plains, the Raven Guard would make their final stand. They had survived for ninety-eight days. They had fought with honour and determination, for no other course of action was possible. The Raven Guard had proven themselves loyal to the end, choosing survival over betraying their oaths, a choice which, Historator Savants can be sure, never once occurred to the Primarch or a single one of his sons. The Raven Guard had been forged in the searing crucible of the Lycaean Uprising, where resistance, however futile, was the only option, even in the face of utterly crushing, hopeless oppression.

The Deliverance
Caught upon a windswept mountainside, Corax's Legion remained resolute. Behind the peak stretched the great salt plains that had forced them into this last, defiant stand. Ahead of them massed the might of the World Eaters, the rage-driven Astartes Legion of Angron, who strode at their head roaring for the blood of his brother. A sea of white and blue World Eaters Astartes spattered with the red of gore swept up from the valley intent on the destruction of the Raven Guard. Maddened by their neural implants and driven into a battle-frenzy by inhuman cocktails of stimulants, the berserk warriors of the World Eaters pounded up the sloping mountainside while their tanks and guns provided covering fire; every warrior bellowed his eagerness to fulfill the blood oaths they had sworn to his Primarch. As Angron's savage challenge rose above the roar of his Legionaries and the first of the Traitors' bolt shells struck amongst the Raven Guard's ranks, Corax issued what all assumed would be his final orders to the last of his proud Legion. Here the Raven Guard would stand; here the Raven Guard would die. But now fresh thunder split the skies above the last battlefield of Istvaan V, and with it came black-winged charnel birds which fell in a fire-spitting flock from the tumult above, their wrath unleashed not upon the few who remained to the Raven Guard but instead upon the World Eaters whose reckless headlong charge to finally grapple with their foe left them exposed before these birds of prey.

A swathe of detonations cut through the ranks of the World Eaters, ripping through their advance companies. Incendiary bombs blossomed in the heart of the approaching army, scattering white-hot Promethium over the steep slopes. Corax looked on with incredulity as blistering pulses of plasma descended from orbit, cutting great gouges into Angron's Legion. The roar of jets became deafening as drop ships descended on pillars of fire: black drop ships emblazoned with the badge of the Raven Guard. The Loyalist Legionaries scattered to give the landing craft space to make planetfall. As soon as their thick hydraulic legs touched the ground, their ramps whined down and boarding gateways opened. The Raven Guard met their rescuers in stunned disbelief. These drop ships were part of a desperate rescue mission that had been devised by Commander Nev Branne, a Raven Guard Captain who had been left in charge of the Legion's homeworld of Deliverance. Without further delay the Raven Guard survivors quickly prepared for embarkation and escaped aboard the drop ships, breaking for orbit and leaving behind the frothing berserkers of the World Eaters, their angry Primarch futilely baying for Loyalist blood. In a storm of shot and shell was Angron denied his bloody prize. In fire had the Raven Guard been almost exterminated, and now in fire were the Raven Guard delivered from Istvaan V, the world the Warmaster had sought to make their tomb.

Corax never knew how Branne had managed to make his way to Istvaan V, but he was grateful for the rescue. Branne himself was reluctant to reveal what lead him to Istvaan V, and considered the topic sensitive since he had only acted after repeated, inexplicable prophetic "dreams" seen by Marcus Valerius, Praefector of the Therion Cohort, the Imperial Army regiment originally mustered on the planet Therion, which was part of the Raven Guard's Expeditionary Fleet. Against the will of his masters, Praefector Valerius risked all to make for the Istvaan System, acting on a certain belief that the Loyalists' mission had failed and that the Raven Lord was in dire need of rescue. In order to launch his rescue attempt, Valerius had first to convince Commander Branne of its necessity, a challenge which very nearly cost the Praefector his life. Yet he prevailed, and the thousand Legionaries tasked with guarding Deliverance, as well as the Therion Cohort, made the impossibly arduous voyage across half the galaxy and more. The rescue force arrived at Istvaan V at the very moment the World Eaters were sweeping down on the last of the Raven Guard survivors, its drop ships snatching them away from the very teeth of death. That a voyage of over fifty thousand light years should result in such a timely rescue is beyond comprehension for many. There are some who claim that it could only have come about through the intervention of the Emperor Himself. Resigned to his fate, Corax felt that deadly absolution at the hands of Angron would have been a righteous end for the XIX Legion, but with all things considered, the Raven Lord was glad that he would survive to fight in the Emperor's name again.

Aftermath
Barely a handful of Loyalist Space Marines escaped with their lives from Istvaan V to bring dreadful word of the further betrayal of four more Space Marine Legions to the Emperor. A critically wounded Corax made the dangerous journey through the Immaterium back to Terra, arriving 133 days after departing the Istvaan System and finally reaching the Sol System -- the heart of the Imperium -- to seek audience with the Emperor. Vulkan was missing and presumed dead, though he would later reemerge after a harrowing journey back to Terra himself, to lead his Legion once more. After the conclusion of the Horus Heresy, Vulkan would be one of the Primarchs who protested Roboute Guilliman's publication of the Codex Astartes and the splitting of the remaining Space Marine Legions into 1,000-man Chapters following the death of Horus. The Salamanders, along with the Iron Hands and the Raven Guard, would spend the remainder of the Horus Heresy rebuilding their decimated Legions and were too weakened to play any further role in the great conflict.

In the days after the battle, the Traitor Legions salvaged a large number of vehicles, wargear and other war materiel from what the Loyalist Legions had left on the field. This salvage was repaired and modified for the Traitor Legions' use and then put back into frontline service to be used against the Imperium. Some of this equipment would still be in service with certain Chaos Space Marine warbands in the late 41st Millennium. Orbital space around Istvaan V was busy as the vessels of 8 Legions assumed formation prior to transit to the system jump point. Over 3,000 vessels jostled for position above the darkened fifth planet, their holds bursting with warriors sworn to the service of Horus. Tanks and monstrous war machines had been lifted from the planet with incredible efficiency and an armada greater than any in the history of the Great Crusade assembled to take the fire of war into the very heart of the Imperium.

Following the victory of the Drop Site Massacre, Horus called a meeting of the Primarchs of all 8 of the Traitor Legions aboard his flagship, the Vengeful Spirit. Five of the Primarchs, including four who had fought at Istvaan V, met in person, including Horus, Fulgrim, Angron, Mortarion and Lorgar. Three appeared through the use of hololithic emitters that transmitted their signals through the Warp, including Perturabo, Night Haunter and Magnus the Red, who had only recently joined the Traitors after the Scouring of Prospero when the broken remains of his XV Legion had been transported by Tzeentch into the Eye of Terror to the Planet of the Sorcerers. The Thousand Sons, bitter at what they perceived as their betrayal by the Emperor, now willingly became the eighth Traitor Legion. The council of Traitor Primarchs made their plans for the next step in their war against the Emperor and then each Legion went its way according to its assigned role.

Unbeknownst to the surviving Raven Guard, Alpha Legion operatives had secretly infiltrated their ranks during the Dropsite Massacre, surgically altering their own operatives to resemble dead Raven Guard Legionaries and then inserting them into Corax's Legion during the chaos of their flight following the slaughter in the Urgall Depression. Alpharius Omegon had been told by the secret alien organisation known as the Cabal that the XIX Legion was going to receive in the future an extremely valuable, top-secret Imperial asset that would be of great use to the cause of Horus. Impersonating Horus, the Alpha Legion Primarchs ordered a pursuing World Eaters fleet to stop all action against Branne's fleeing ships, so that the Raven Guard would survive the slaughter on Istvaan V and come into possession of the asset, which the Alpha Legion's infiltrators could then steal.

The fleets of Angron, Fulgrim, Mortarion, Lorgar and Horus' own Legion would rendezvous at Mars, now that word had come from the Tech-priest Regulus, the Mechanicus' liasion with the 63rd Expeditionary Fleet, of that planet's fall to Horus' supporters within the Mechanicus during the internecine conflict known as the Schism of Mars. With the manufacturing facilities of Mondus Gamma and Mondus Occullum wrested from the control of the Emperor's forces, the forges of Mars were free to supply the Warmaster's army. The eager warriors of the Alpha Legion were singled out by Horus for a vital mission, one upon which the success of the entire venture could depend. Following Horus' manipulation of Leman Russ into assaulting the homeworld of the Thousand Sons, the Space Wolves were known to be operating in the region of Prospero. In the nearby system of Chondax, the White Scars of Jaghatai Khan were sure to have received word of Horus’ rebellion and would no doubt attempt to link up with the Space Wolves. Horus could not allow such a grave threat to appear, and so the warriors of Alpharius were to seek out and attack these Legions before they could join forces.

The Night Haunter's fleet had already departed, bound for the planet of Tsagualsa, a remote world in the Eastern Fringe that lay shrouded in the shadow of a great asteroid belt. From there, the Night Lords' terror troops would begin a campaign of genocide against the Imperial strongholds of Heroldar and Thramas, star systems that, if not taken, would leave the flanks of the Warmaster's strike on Terra vulnerable to attack. The Thramas System was of particular importance, as it comprised a number of Mechanicus Forge Worlds whose loyalty was still to the Emperor. The ships of the Iron Warriors prepared to make the journey to the Phall System where a large fleet of Imperial Fists vessels were known to be regrouping after a failed attempt to reach Istvaan V in time to join the Loyalist assault. Though Rogal Dorn's warriors had played no part in the drop site massacre, Horus could not allow such a powerful force to remain unmolested. The enmity between bitter Perturabo and proud Dorn was well known, and it was with great relish that the Iron Warriors set off to do battle with their old rivals. With his flanks covered and the Space Marine forces that could potentially reinforce the heart of the Imperium soon to be embroiled in war, the Traitors were ready to unleash 7 Terran years of devastating civil war upon the Imperium in the name of Horus and the Dark Gods.