Drop Site Massacre

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

- Attr. 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
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, ordered seven Loyalist Space Marine Legions to Horus' base on the world of Istvaan V to challenge the Warmaster's rebellion. 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. 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.

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
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
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.

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
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.

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.

Dropsite Massacre
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
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. Imperial history does not record the fate of these surviving Salamanders or their missing Primarch Vulkan. 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. Within hours the slaughter was complete and almost the entire strength of three complete Space Marine Legions lay silent and dead on the tortured sands of Istvaan V.

Raven's Flight
Corax had survived the crash of his gunship and quickly ordered the remaining warriors of his Legion to regroup. He learned to his shock that a large percentage of the Raven Guard had been utterly annihilated during the ensuing slaughter. The Loyalist survivors took to the highlands of the surrounding hills, hiding from their relentless pursuers. During their flight, the Raven Guard's position was nearly discovered by a roving armour column of traitorous Iron Warriors, but they were destroyed in a Raven Guard ambush and wiped out before they could report what they had learned.

Thirty standard days after the initial planetary assault, the future looked grim for the fleeing Raven Guard survivors. They had received no word from either the surviving Iron Hands or Salamanders Legions. Corax ordered his warriors to dig-in and hold position on Lurgan Ridge while he undertook a lone reconnaissance of their original drop site to determine their options. Utilising his innate psi-abilities to escape detection, Corax successfully conducted a reconnaissance of the Traitor Legions' positions around the heavily fortified drop site. Though the Primarch informed his men that his mission was to reconnoiter the drop site, his primary objective was to scour the Urgall Plateau for the bodies of his fallen sons, but he failed to find them.

After 98 standard days of relentless pursuit by the victorious Traitors, the Raven Guard survivors were finally backed into a literal corner. 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 he had sworn to his Primarch.

But before they could utterly eradicate the surviving Raven Guard Astartes, the World Eaters were attacked from an unexpected quarter. Broad-winged aircraft plunged down from the scattering of clouds, missile pods rippling with fire. 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 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.

Meanwhile, the Alpha Legion had secretly infiltrated the Raven Guard during the Drop Site Massacre, surgically altering their own operatives to resemble dead Raven Guard Astartes and then inserting them into Corax's Legion during the chaos of the chase on Istvaan V. 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.

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. Deadly absolution at the hands of Angron would have been a righteous end for the XIX Legion, but with all things considered, Corax was glad that he would survive to fight in the Emperor's name again.

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.

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.

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 read to unleash 7 Terran years of devastating civil war upon the Imperium in the name of Horus and the Dark Gods.