Drop Site Massacre

The Drop Site Massacre of Istvaan V was one of the major turning points that occurred during the great galactic civil war that engulfed the Imperium of Man in the early 31st Millennium known as the Horus Heresy. During the massacre three Loyalist Space Marine Legions -- the Iron Hands, the Salamanders and the Raven Guard -- were betrayed by 4 other Legions they believed were loyal to the Emperor of Mankind, but in fact had already betrayed the Imperium and turned to the service of the rebellious Warmaster Horus and Chaos.

History
The Istvaan System’s third world, comfortably close enough to the sun to support human life, was now a virus-soaked mass grave marking the anger of Horus Lupercal. 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 a single day. The orbital bombardment from the Warmaster’s fleet, payloads of incendiary shells and virus-laden biological warfare pods, had seemingly spared nothing and no one anywhere in the world. Istvaan III lingered now 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 Legions of Horus made their way to Istvaan V, a flotilla of powerful warships and carriers bearing the martial pride of four 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, dark priest of the Machine ministering to the Dies Irae and its sister Titans as they prepared to unleash the unimaginable power of these land battleships once more.

Final victory on Istvaan III had been bought with many lives, but in its wake the Legions were tempered in the crucible of combat to do what must be done to save 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, the Warmaster promised. The Warmaster would strike a vicious blow against the Imperium and the False Emperor - a blow that would resonate down the millennia for all time.

The Phoenician & The Gorgon
As the Warmaster 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 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's 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 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 alien fortresses on Istvaan V and prepare it 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, he could entrust this vital task to no other. Fulgrim supervised the vast teams of Mechanicum 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 them, they were going to have to come down to the surface to do so.

Mobilising for War
Overcome with mind-numbing rage at such 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 7 Loyalist Space Marine Legions to Horus' base on the world of Istvaan V to challenge the Warmaster. 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 Raven Guard. The Legions comprising the second 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
Ringing Isstvan 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, with the scouts, cruisers, destroyers and command ships of seven entire Legions. With a precision that required mass calculation, the fleets of seven Astartes Legions hung in the skies above Isstvan V. 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, traitorous son of the Emperor, was making his stand on the surface. The Imperium of Man had sent seven Legions to kill its wayward scion, little knowing four of them had already spat on their oaths of allegiance to the Throneworld.

Aboard 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; Nighthaunter, Alpharius Omegon and Perturabo. Lorgar strode to the centre of the gathering of Traitors. He then proceeded to impress upon the gathering of his sons, brothers and cousin Astartes of 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 and 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 lies. The Imperium was forged by a dangerous deceit, and had eroded them all by demanding they sacrifice truth on the altar of necessity. This was an empire, propagated by sin, that deserves to die. And here, on Isstvan V, they would begin the purge.

From the ashes 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. The Emperor believes them loyal. Their four Legions were ordered to Istvaan V on His misguided conviction alone. But their coalition here and now was the fruit of decades’ worth of planning. It was ordained, and brought about according to ancient prophecy. No more hiding in the shadows. No more manipulating fleet movements and falsifying expeditionary data. From this day forward, the Alpha Legion, the Word Bearers, the Iron Warriors and the Night Lords would stand together – bloodied but unbowed beneath the flag of Warmaster Horus, the second Emperor. The true Emperor. First Captain Sevatar of the Night Lords Legion uttered, 'Death to the False Emperor,' becoming the first living soul to utter the words that would echo through the millennia. The curse was taken up by other voices, and soon it was being 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 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 be done.

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 pounded the Urgall 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 keep, the Warmaster 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 for the initial 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 Hereteks Adepts of the Dark Mechanicum unleashed perversions of ancient technology stolen from the Auretian Technocracy to wreak bloody havoc amongst the Loyalists. 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. 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 have been embattled for almost three hours with no clear victor emerging. Even now, the loyalists wait for the second wave of 'allies' to make planetfall, believing they would be reinforced for their final advance. The traitors all knew their parts to play in this performance. They are all aware of the blood they must shed to spare their species from destruction, and 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 secured the 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 loyal 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 scythe.

And Horus, 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. 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 wave burned through the atmosphere on screaming thrusters. The sky fell dark with the weak sun eclipsed by ten thousand avian shadows, and the cheering roar sent up by the loyalists was loud enough to shake the air itself. 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 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 First 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 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 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 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. The Iron Hands had damned themselves by remaining in the field.

The Raven Guard 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, beams of achingly bright laser 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 prepared 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. Erebus 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 senses but 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 ago when Ferrus had presented him a weapon he had forged. He had crafted the fine crozius-maul, Illuminarum, as thanks for the reinforcement of the X Legion at Galadon Secondus. Snapping back to reality, the seed of doubt krept 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 as to the fate of his brother Vulkan, nothing was known. In the meantime, the second wave of Traitor Legions that had turned upon their former allies began to slaughter them 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 true brothers could be, fought a bitterly contested, titanic struggle.

The Death of Ferrus Manus
Ferrus Manus and his Morlocks charged through the shattered ruin of the defences, 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 of such mighty suits of armour. 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.

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 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 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. 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 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 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. 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 he had 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 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 of delivering the deathblow 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 party to. He 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 shared 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. Lord Corax, Primarch of the Raven Guard 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 Astartes known as the Gal Vorbak, Lorgar's "Blessed Sons," leapt forward to meet their end at the hands of a 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 ago. As the Word Bearers primarch hammered his way through the Raven Guard to reach his brother, he felt power seethe within him, aching to rise out. Always, 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, and thus, he 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 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 Possessed Chaos Space Marines. 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 of the future visions he had seen of their father -- a bloodless corpse, enthroned upon a throne 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. Even should Lorgar somehow manage to escape his ultimate fate this day, he would bear these scars until the day he died.

The two primarch 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. 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. Even as he tightened his grip on Corax's throat, 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 couldn’t free himself. The Raven Lord gave no ground, even as a second, third and fourth head butt decimated his delicate features. The claws 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 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 in twenty who'd 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 Curze. 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. As bit out another retort, his words 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 site, 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 ones. The path to Terra was now 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
The outnumbered Loyalists were then surrounded and brutally butchered. 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 Emperor-class Titan Dies Irae, the Traitors killed tens of thousands of Loyalist Astartes. At the height of the massacre the Warmaster Horus entered the fray, at the head of the elite Sons of Horus Terminators known as the Justaerin, slaughtering the Loyalists in wrathful anger.

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's fleet. Despite the odds arrayed against them, some of the Loyalists on the ground managed to survive against these odds -- 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 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.

Raven's Flight
Corax had survived the crash and quickly ordered the remaining warriors of his Legion to regroup. He learned to his shock that a large percentage of his Legion had been utterly annihilated during the ensuing slaughter. They took to the highlands of the surrounding hills and took to the shadows, hiding from their relentless pursuers. During their flight, their 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 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 at 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 days of relentless pursuit, the Raven Guard survivors were finally backed into a literal corner. Caught upon the 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 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 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 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 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.

Aftermath
Barely a handful of Loyalist Space Marines escaped with their lives from Istvaan V to bring word of the further betrayal of four more Astartes 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 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 Chaos Space Marine warbands in the 41st Millennium. In the days after the Drop Site Massacre, the Warmaster 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 Legion had been transported by Tzeentch into the Eye of Terror. 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, unleashing 7 Terran years of devastating civil war upon the Imperium in the name of Horus and the Dark Gods.