Gaiaterra: Elysea's Conflict/The Horus Heresy

The Horus Heresy, sometimes referred to poetically as the "Age of Darkness," was a civil war that consumed the Coalition for 9 years. Its outbreak marked the end of the Coalitions Great Crusade to reunite the scattered clans under a single government and the beginning of the current Age of the Coalition. The Horus Heresy is in many ways the founding event of the Karak Overlord Coalition as it now exists and the general discovery of the Heralds of Chaos.

The civil war began following the corruption by the Ruinous Powers of Chaos of the Coalition Warmaster Horus Lupercal, the primarch of the Children of Horus Legion, and the most beloved Astarte of the Votann. The Chaos Gods fed Horus' innate ambition and sense of betrayal by the Coalition until he turned upon his nation and sought to claim the Coalition for his own.

Horus convinced half of the other Primarchs and Space Marine Legions, as well as large swathes of the Coalition Army, to turn Traitor alongside him and unleash a cataclysmic attempt to conquer Gaiaterra in his name.

Over 9 years the war raged, 7 of them consumed by Horus' drive on the Coalitions capital, until coming to a final cataclysm on Karaz-A-Karak itself where Horus was slain, His dreams of creating a future of his desire forever broken.

The conflict was fought across the Gaiaterra early in the first century of the (insert date) and resulted in more than 2.3 million dead, 4.6 million if one includes the populations purged by the Grey Steel Order after the Heresy due to the taint of Chaos corruption.

The Heresy concluded with the death of the traitorous Warmaster Horus and the exile into the Eye of Terror of the Heretic Astartes Traitor Legions.

The Heresy was directly responsible for the birth of the present-day structure of the Space Marine Chapters following the Second Founding and the reorganization of the Imperium by the Ultramarines' Primarch Roboute Guilliman as lord commander of the Imperium and Imperial Regent during the Time of Rebirth in the (insert date).

In Gaiaterra: Elysea's Conflict, It serves as a background for the Karak Overlord Coalition and the Heralds of Chaos and the war itself would later become featured in the DLC Tacitus story.

The Great Crusade
When the great (insert event) that had forced the Coalition to hide in their mountains since the end of the (insert) subsided, and the Age of Strife came to an end at the dawn of the (insert) V.C., the Votann deemed it time to begin the Great Crusade, a massive campaign to conquer the mountain range by which they and its armies would free all Coalition-settled colony worlds from enemy oppression or primitive ignorance and reunite the Aio and Dwarf race across the Durin under the single banner of the new Coalition. To execute this plan, the Votann created the Astartes, god-like, genetically-engineered superhuman offspring.

In time, many of the Space Marines in the Legions, especially those recruited from their primarchs' homeworld rather than from Terra before the primarchs' rediscovery, would come to venerate and feel more loyalty for their primarch than Elysea's children.

Corruption of the Space Marine Legions
Long before the tragic events that would unfold on Isstvan and initiate the conflict of the Horus Heresy, the Primarch Lorgar of the Word Bearers Legion had already committed themself and their Astartes to the service of the Ruinous Powers.

Lorgar was a puritanical religious zealot who was said to have experienced visions that foresaw the coming of the Gods, who he believed to be a living god. This belief resulted in a series of bitter religious wars as Lorgar fought to impose his new religious doctrine worshipping the Emperor on his hometown of Colchis.

When the Coalition finally arrived the entire world was already enthralled to Lorgar and their cult of the Votann. The people of Colchis united behind their new God-Emperor. The elaborate celebrations and displays of piety lasted for months, although it was said that the Votanns did not approve of this, wishing their forces rejoin the Great Crusade as soon as possible and being greatly dismissive of organised religion in general as a vioilation of the Imperial Truth.

The Votann had not begun the Great Crusade to reshackle Humanity within the chains of superstition and ignorance but to spread the light of reason and science. At the conclusion of the celebrations, Lorgar was made master of the XVIIth Space Marine Legion, the Imperial Heralds, who were renamed the Word Bearers after they embraced their primarch and his religious beliefs.

Kor Phaeron, Lorgar's adoptive father and religious advisor, survived the augmentation process to join the Word Bearers as a rare adult Space Marine, though he would never be a true Astartes. Kor Phaeron became Lorgar's chief adviser, lieutenant and the commander of the Word Bearers' elite 1st Company as the XVIIth Legion's first captain.

Lorgar led his Legion throughout the Great Crusade, as the Word Bearers sought to eliminate all blasphemy and heresy within the new Imperium of Man. Ancient texts and icons of other faiths were burned. The construction of vast monuments and cathedrals venerating the Votann as the God of Mankind were supervised by Lorgar and the Word Bearers on many of the worlds they brought into Imperial Compliance.

The greatest Chaplains of the Word Bearers produced enormous works on the divinity and righteousness of the Emperor, and gave grand speeches and sermons to the masses of conquered worlds. The progress of the Word Bearers was slow in bringing new worlds into Imperial Compliance, but the Imperial domination of those who were defeated by the XVIIth Legion was always complete, as religion proved to be a potent tool in securing Imperial loyalty.

At some point during this period, Lorgar penned the work known as the Lectitio Divinitatus, which laid out the case that the Emperor of Mankind was a divine being and was worthy of worship as the rightful God of humanity.

During the Great Crusade, it became apparent that the Primarchs were far from the perfect specimens of humanity they were intended to be. Although each Primarch was physically and mentally god-like compared to a baseline human being, they harboured the flaws of vanity, egotism, hunger for power, jealousy, arrogance, insecurity and all the other sins of the human character.

As the Warmaster, Horus took over command of the Great Crusade, and accepted his new duties with earnest dedication. However, there was much dissension in the ranks of the Primarchs and other parties in the Imperium over the Emperor's decision to withdraw from the campaign and return to Terra as well as to reorganise the administration of the Imperium. Only a handful of the Primarchs, among them a scheming Lorgar, remained steadfast beside the Warmaster during this period of conflict. Horus also disagreed with many of the decrees passed by the newly established Coalition Council, intended to shift the burden of taxation and administration onto the newly-conquered ("Coalition Compliant") citites. Even worse, Horus came to believe in his heart that he was failing his nation, and was deeply wounded that the Council had revealed to none of the Primarchs, not even their most favoured general, why he had secluded himself upon Terra and the truth behind his secret Webway Project. These seeds of bitterness, resentment and frustration grew, and would soon bear deadly fruit.

It was in the city of Davin that Horus' fate was sealed. This was the second time his Legion had been posted to this world; after the previous visit sixty years earlier the Luna Wolves had adopted the native Davinite institution of warrior lodges. Though these lodges had begun as simple fraternities of warriors, their secretive nature handed Lorgar, the Primarch of the Word Bearers Legion and their First Chaplain Erebus, the tool they needed to manipulate Horus towards the service of the Chaos Gods.

Lorgar and their Word Bearers originally came from Colchis, a world defined by religious fanaticism, and had long worshiped the Emperor as a god. The Word Bearers had sought to spread their Cult of the Emperor to every world they added to the Imperium. But the Emperor deeply disliked and mistrusted organized religion (ironic, since he had often been the focus for much of it in his various guises across history), blaming it for much of the darkness that had plagued humanity's history. The Emperor openly and publicly refuted his alleged divinity and banned religious worship in his empire. Lorgar did not suffer the Council reprimand or views on religion well. Angered and wounded that the Council would not accept his devotion and worship, Lorgar turned instead to the Ruinous Powers of the Warp -- who were all too willing to accept the devotion of one of Coalition Primarchs. Before long, the Word Bearers Legion had been almost entirely corrupted by the Chaos Gods, and Lorgar and Erebus were tasked by the Ruinous Powers with corrupting all of their fellow Space Marines -- starting with the greatest of them all, the Warmaster Horus.

During a battle against Chaos-spawned undead in Davin, whose Planetary Governor, Eugen Temba, had been corrupted by the forces of the Chaos God Nurgle, Horus was poisoned by a xenos blade dedicated to Nurgle known as a Kinebrach Anathame that had been stolen from the human civilisation of the Interex by Erebus after Horus and the Luna Wolves of the 63rd Expeditionary Fleet had made a disastrous first contact with them. Erebus then gifted the weapon to the Chaos-corrupted form of the Imperial Army commander Eugen Temba who the Warmaster had left behind to govern Davin sixty years before. Temba had turned to the worship of Nurgle in the interim, being transformed into a bloated mutant and killing off most of his Coalition Army garrison in the process, transforming them into undead Plague Zombies that the Luna Wolves were forced to mow down in waves. Horus personally faced off with the mutant that had been Temba aboard the grounded ruins of his Imperial Cruiser. In the course of that battle, the potent living metal of the Chaos blade wielded by the plague-infused monstrosity left Horus with a bleeding, toxic wound in his shoulder that his Legion's Apothecaries could not heal despite all the advanced technology available to them. Seeing his chance to further the designs of Chaos, Erebus next persuaded the Luna Wolves' warrior lodge to allow a group of Davinite shamans -- Chaos Cultists all -- located in Davin at the Temple of the Serpent Lodge to heal him. The Luna Wolves, besides themselves with grief and the fear that their beloved Primarch would die, agreed to the suggestion.

During the dark rituals that followed within the temple, Horus' spirit was transferred from his body into the Immaterium. There, he bore witness to a nightmare vision of the future. The Dark Gods portrayed themselves as victims of the Emperor's psychic might and claimed that they had no real interest in the happenings of the material world. Magna the Red, the sorcerous Primarch of the Thousand Sons Legion, had also travelled into the Warp via sorcery to try and stop Horus from turning to Chaos. Magna explained that the Warmaster's vision was only one of many possible futures, but one that Horus alone could prevent. Horus, already jealous and resentful of the Emperor, proved all too receptive to the Ruinous Powers' false vision. The Chaos Gods' pact with Horus was simple: "Give us the Coalition and we will give you Gaiaterra." Driven by his jealousy and desire for power Horus accepted the Ruinous Powers' offer. They healed his grievous wound and filled him with the powers of the Warp. Renouncing his oath to the Coalition, Horus led his Legion, renamed the Children of Horus, into worship of the myriad Chaos Gods in the form of Chaos Undivided. He then sought to turn many of his fellow Primarchs to the service of Chaos, and succeeded with Angron of the World Eaters, Fulgrim of the Votann's Children and Mortarion of the Death Guard, who were the first of many to follow, along with many regiments of the Imperial Army and several Titan Legions of the Adeptus Mechanicus.

Magna the Red, the Primarch of the Thousand Child Legion, foresaw Horus' actions through her Legion's own use of psychic sorcery. Magna then attempted to forewarn the Coalition of the impending betrayal. However, knowing that she would have to find a means of quickly warning the Emperor, Magna used sorcery to send her message to the Emperor. Refusing to believe that Horus, the Coalitions most trusted Primarch, would actually betray them, the Coalition instead mistakenly perceived the traitor to the Imperium to be Magna and her Thousand Child, who had long suffered from a near-debilitating run of mutations because of the Heralds and Tzeentch sabotage. The Coalition ordered the Primarch Lemia Russ, Magna greatest rival, to mobilise her Valkyrie Wolves Legion and the witchhunters known as the Sisters of Silence and take Magna into custody to be returned to Karaz-A-Karak to stand trial for consorting with the Chaos Gods. While en route to the Thousand Child's Legion's city of Prospero, Horus convinced Russ, who had always been repelled by Magna's reliance on psychic powers, to launch a full assault on Prospero instead even though Magna had been entirely willing to face the Coalition judgment once she realized she was being manipulated by the entities that called the Immaterium home.

Isstvan Massacres
Unknown to the Coalition, the Word Bearers Legion had been devoted to Chaos Undivided for some time before this event. The Governor of Isstvan, Vardus Praal, had been corrupted by the Chaos God Slaanesh whose cultists had long been active on the world. Praal had declared his independence from the Coalition, and practiced forbidden sorcery, so the Council of Coalition charged Horus with the retaking of that world, primarily its capital, the Choral City. This order merely furthered Horus' plans to overthrow the Coalition. Although the four Legions under his direct command -- the Sons of Horus, the World Eaters, the Death Guard and the Votann's Children -- had already turned Traitor and now pledged themselves to Chaos, there were still some Loyalist elements within each of these Legions that approximated one-third of each force; many of these warriors were Coalition-born Space Marines who had been directly recruited into the Astartes Legions by the Votann itself before being reunited. Horus, under the guise of putting down the rebellion, amassed his troops into Isstvan.

Horus had a plan by which he would destroy all the remaining Loyalist elements of the Legions under his command, a plan that would ultimately unfold into the nightmare of what Coalition historians would later name the Isstvan Atrocity. After a lengthy bombardment of Isstvan, Horus dispatched all of the known Loyalist Astartes down to the planet, under the pretense of bringing it back into the Coalition. At the moment of victory and the capture of the Choral City, the planetary capital of Isstvan, these Astartes were betrayed when a cascade of terrible virus-bombs fell onto the city, launched by the Warmaster's bombers. Captain Saul Tarvitz of the Votann's Children, however, was aboard his Legion's capital Andronius and discovered the plot to wipe out the Loyalist Astartes of the Traitor Legions. He was able, with help from Battle-Captain Nathaniel Garro of the Death Guard who was in command of the Death Guard frigate Eisenstein, to reach the surface of Isstvan despite pursuit and warn the Loyalist Space Marines he could find of all four Legions of their impending doom. Those that heard or passed on Tarvitz's warning took shelter before the virus-bombs struck. The civilian population of Isstvan received no such protection: eight billion people died almost at once as the lethal flesh-dissolving virus called the Life-Eater carried by the bombs infected every living thing on the planet. The Primarch of the World Eaters, Angron, realising that the virus-bombs had not been fully effective at eliminating all the Loyalists, flew into a rage and hurled himself at the planet with 50 companies of Traitor Marines. Discarding tactics and strategy, the World Eaters Legion's Traitors worked themselves into a frenzy of mindless butchery. Horus was furious with Angron for delaying his plans, but the Warmaster sought to turn the delay into a victory and was obliged to reinforce Angron with troops from the Sons of Horus, the Death Guard, and the Votann's Children. Fortunately, a contingent of Loyalists led by Battle-Captain Garro escaped Isstvan aboard the damaged Coalition frigate Eisenstein and fled to Karaz-A-Karak to warn the Council that Horus had turned Traitor.

On Isstvan, the remaining Loyalists, under the command of Captains Tarvitz, Garviel Loken and Tarik Torgaddon, another Loyalist member of the Sons of Horus, fought bravely against their own traitorous kin. Yet, despite some early successes that delayed Horus' plans for three full months while the battle on Isstvan played out, their cause was ultimately doomed by their lack of air support and firepower. During the battle the Sons of Horus Captains Ezekyle Abaddon and Horus Aximand were sent to confront their former Mournival brothers, Loken and Torgaddon. Horus Aximand beheaded Torgaddon, but Abaddon failed to kill Loken when the building they were in collapsed. Loken survived and witnessed the final bombardment of Isstvan that ended the Loyalists' desperate defence. To prove his worth and loyalty to Lord Commander Eidolon of the Votann's Children -- and thus to his Primarch, Fulgrim -- Captain Lucius of the 13th Company of the Emperor's Children, the future Champion of Slaanesh known as Lucius the Eternal, turned against the Loyalists that he had fought beside because of his prior friendship with Saul Tarvitz. Lucius slew many of them personally, an act for which he was then accepted back into the Votann's Children on the side of the Traitors. In the end, the Loyalists retreated to their last bastion of defense, only a few hundred of their number remaining. Finally, tired of the conflict, Horus ordered his men to withdraw, and then had the remains of the Choral City bombarded into dust for a final time from above.

The Drop Zone Massacre
The Isstvan archipelago's third island 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. Isstvan III lingered now in silent, almost grand in the extent of its absolute devastation, serving as the scarred tombstone for the death of an empire.

Ringing Isstvan V was one of the largest fleets ever gathered in the history of the Coalition. 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 around the shores of Isstvan V. Shuttles and landing craft 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 Coalition, was making his stand on the surface. The coalition had sent seven Legions to kill its wayward scion, little knowing four of them had already spat on their oaths of allegiance to the Coalition.

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, Alphara Omegan and Perturabo. Lorgar strode to the center of the gathering of Traitors. They then proceeded to impress upon the gathering of their children, siblings 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 Coalition 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 Coalition 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 Coalition believes them loyal. Their four Legions were ordered to Isstvan V on 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!"

Thousands of Drop Pods and Stormbirds were deployed 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 Gabriela Santor, and 10 full companies of elite Morlocks Terminators charged straight into the center 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 Isstvan 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 walked the planet’s surface and death followed in their wake. The blood of heroes and traitors flowed in rivers. 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 had been embattled for almost three solar hours with no clear victor emerging. The Loyalists waited for their second wave of "allies" to make landfall, believing they would be reinforced for their final advance. In truth, the Traitors all knew their parts to play in this performance. They were all aware of the blood they would shed to spare their species from what they believed to be its coming destruction, and install Horus as the new Master of Mankind.

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. Overwhelmed with rage, the headstrong Ferrus Manus disregarded the counsel of his sister and sibling Corax and Vulkan and hurled themself against the fleeing rebels, seeking to bring Fulgrim to personal combat. Their veteran troops -- comprising the majority of the X Legion's Terminators and Dreadnoughts -- followed. 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 Isstvan V. For all the wrong reasons, this battle would go down in the annals of Coalition and Herald 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 Legions' 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 Jump Pack; Ferrus Manus of the Iron Hands at the heart of the battlefield, their silver hands crushing any Traitors that came within reach, while they pursued and dragged back those who sought to withdraw; and lastly, Vulkan of the Salamanders, armoured in overlapping Artificer Armour, thunder clapping from their warhammer as it pounded into yielding ceramite 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 chainblades left and right, barely cognizant of who fell before him; Fulgrim of the newly-named Slannesh's Children, laughing as they deflected the clumsy sweeps of Iron Hands warriors, never stopping in their 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 their great war scythe.

And Horus, Warmaster of the Imperium, the brightest star and greatest of the Coalitions Primarchs. 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 Coalitions 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.

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 Isstvan V. Yet the Space Marine Legions of the reserve were no longer loyal to the Coalition, 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 Alphara represented a force larger than that which had first begun the assault on Isstvan 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 Clockwork Drones 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 their 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 Manus looked on in stunned horror as Fulgrim laughed at the look on their sibling's face as the forces of their "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.

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 she slew them with impunity. Seeing the slaughter of their most favoured children, Lorgar intervened and prevented the death of the remaining Gal Vorbak Astartes. The two opposing Primarchs then duelled one another in close combat, and the Raven Guard's Primarch quickly gained the upper hand over her outmatched brother. Lorgar had always been more of a scholar than a warrior and Corax prepared to execute them for their betrayal of the Coalition. Lorgar was spared from execution by the intervention of the Night Lords' Primarch, Konrad Curze, at the last moment. The Night Haunter and the Raven fought a brutal melee. Curze quickly gained the upper hand over his battle-weary sister and prepared to slay her, but Corax managed to escape death by taking to the sky with her master-crafted Jump Pack.

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, while sending out distress signals in the hopes that the Dwarfen and Aio forces nearby could send aid. 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 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.

The, by some miracle, the emergency was heard and help had came. As the Traitors were soon bombarded by dwarfen ships and Aio aircraft. With the cobined forces making landfall and charging into the stunned traitors, smashing them aside and forming a corridor for the Loyalists to escape 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. Coalition history does not record the fate of these surviving Salamanders or their missing Primarch Vulkan. The Raven Guard's Primarch just managed to board an LCAC, escaping with her legion.

Roughly half of the Loyalist Space Marines escaped with their lives from Isstvan V, thanks to the Dwarfs and Humans, to bring dreadful word of the further betrayal of four more Space Marine Legions to the Council. A critically wounded Corax made the dangerous journey through the sea back to Terra, arriving 14 days after departing the Isstvan island and finally reaching the Durin Mountains -- the heart of the Coalition -- to seek an audience with the Council. Vulkan was missing and presumed dead, though they would later reemerge after a harrowing journey back to Durin himself, to lead his Legion once more. And Ferrus was confirmed dead, decapitated by Fulgrim, with his Legion managing to grab their Primarch body and head, letting the Coalition give them a proper burial. The Salamanders, along with the Iron Hands and the Raven Guard, would spend the remainder of the Horus Heresy conducting gurerilla warfare, as all three were too weakened to fight head-on, and supporting their sibling's legion and the Coalition forces.

Siege of Karaz-A-Karak
The Siege of Karaz-A-Karak began with an aerial bombardment by the Warmaster Horus' airforces as the prelude to invasion. Although the Loyalist fleets and defenders fought back and the massive defenses on Luna reaped more than a quarter of the bombers in the Traitor fleet they, like the Loyalist soldiers on the surface, were too few to face the combined forces of so many Traitor Legions and were mowed down without mercy. After days of bombardment, the Chaos Space Marines landed on the surface of Terra in Drop Pods and advanced on the two spaceports nearest the location of the Imperial Palace to secure them in preparation for the main landings of the Traitor forces. Elements from five of the Traitor Legions participated in the battle, aided by the Traitor forces already on the surface. Despite the brave efforts of the Loyalists, the Eternity Wall and the Lion's Gate Port fell within hours to the Forces of Chaos. Dark Chaos Cultists made their invocations, calling down the Greater Demons of Chaos from the Warp directly onto Coalition soil. With the Port secured, Horus' remaining troops of the Traitor Legions and their Traitor Coalition Army landed en masse, and the hulking transports carried thousands of troops each. They also landed the terrible Traitor Titans that served the Warmaster's cause and had been infected with the demonic power of Chaos. The transports' immense size made them prime targets for Karaz-A-Karak defense howitzers. Although many of the Traitor landing craft were destroyed at sea, many more made it to the surface, disgorging yet more soldiers, main battle tanks, and Traitor Titans to add to the besiegers' strength. They met stiff resistance from the Loyalists as the Coalition defenders knew that the survival of their home and the future of the entire Coalition rested on their shoulders.

The Chaos besiegers forced the Coalition defenders back to the walls of the Palace, where thousands died slowing the assault. The Primarch Angron of the World Eaters Legion, now a Demon Prince of the Blood God Khorne, came forth before the walls of the Palace and demanded the Loyalists' surrender, saying that they were cut off, outnumbered, and defended a ruler unworthy of their loyalty. Many would have surrendered to Angron after seeing the sheer power of the Forces of Chaos that stood arrayed before them had it not been for the Primarch Sanguinia, the winged and seemingly angelic leader of the Blood Angels Legion. The two Primarchs, once brother and sister, gazed at each other, perhaps communicating telepathically. Eventually Angron withdrew from before the gates of the Imperial Palace, telling his forces, not without some relish at the prospect of slaughter, that there would be no surrender.

The siege of the Imperial Palace then began in earnest. Three times the Forces of Chaos scaled the walls, and three times were hurled back by Sanguinia and her Blood Angels. Outside the Palace walls, Space Marine and Imperial Army forces led by Jaghatai Khan, the Primarch of the White Scars Legion, unsuccessfully tried to draw the bulk of the besiegers' army away from the Palace. Soon the outnumbered defenders were pushed back into the maze of corridors and bulwarks within the Palace walls. Frustrated with his army's slow progress, Horus ordered the Legio Mortis (Death's Head Legion) to demolish entire sections of the wall. Despite grievous losses, the Titans, led by the infamous Imperator-class Battle Titan Dies Irae, gouged open breaches in the Imperial Palace's defences, which the Traitors then flooded through.

Facing a breach and potential collapse of the Coalition defenses, Jaghatai Khan decided on a change of plan. Rather than assaulting the almost-invincible flanks of the Chaotic army, Khan redirected his highly mobile White Scars Space Marines and the surviving Loyalist Tank Divisions of the Coalition Army to Lion's Gate Port. At dawn Jaghatai's lightning raid caught the Traitor garrison at the Port completely by surprise, and reclaimed the Port for the Imperium. The Khan ordered his troops to reactivate the Port defenses to prevent the Traitor fleet from bringing down any more troops and equipment and form a defensive perimeter to hold their newly reconquered territory. Khan's troops repelled several frenzied counter-attacks from the Traitors, and began firing on Horus' unprotected ships. The Khan's plan worked perfectly: the flow of the Traitors' men and machines to the Imperial Palace had been cut in half at a single stroke. Inspired by this success, the Loyalists also tried to seize back the Eternity Wall Port, but were driven back by the Chaos forces without difficulty, as they had reinforced their garrison following the loss of the Lion's Gate.

Inside the Palace, the defenders had been forced back to the Eternity Gate, the sole point of entry into the inner sanctum of the Palace. The Astartes of the Blood Angels and Imperial Fists tried to hold back the attacking Chaotic troops, while the remaining Loyalists made it through the Gate. Soon the mighty Bloodthirster Greater Daemon Ka'bandha came forth and bellowed out a challenge to Sanguinia in the name of his master Khorne. The demon hurled itself at the Angel of Baal, barely allowing her time to parry the daemon's strikes. The two took to the air, trading blows and battle cries high above the heads of the two forces. Already fatigued from the long siege, Sanguinia was cast down by the demon, pulverising the concrete below upon impact. The Loyalist forces seemed to collectively groan at the fall of their great champion.

Yet the Blood Angels' Primarch was not beaten, only stunned by the force of the impact. Sanguinia cleared her head, forced herself back to her feet, and once again took to the sky. The Angel seized the gloating daemon, holding it by the right ankle and arm. The Primarch hefted the creature high and broke its back over her knee, before hurling the daemon's carcass back at the besiegers, who howled in despair as the last Loyalists fell back and made it into the Imperial Palace's inner sanctum before the great portal of the Eternity Gate was shut tight behind them. Of course, as a demon, Ka'bandah could not truly be slain, only banished to the Warp for a 100000 years, but the Bloodthirster's spirit was sent howling back into the Immaterium to meet the displeasure of his master the Blood God.

The Eternity Gate was closed.

Death Of The Traitor
The siege of Karaz-A-Karak following the initial assault on the Palace lasted for 55 days. Both sides knew that the defeat of the Coalition was near after the defence of the Eternity Gate. Sensing this, and knowing that he must complete the siege before the arrival of Loyalist reinforcements from the other Space Marine Legions that were already on their way, Horus prepared to teleport to the surface from his ship, the Vengeful Spirit, to lead his forces in person. Before this could happen, the Word Bearers' First Chaplain Erebus broke the news to Horus: their demonic allies in the Warp had informed them that the Dark Angels and Space Wolves Legions were nearing Terra; and the Ultramarines were only a short distance behind.

At that moment, Horus despaired; his gamble had failed, weeks of further conflict would be needed to break the defenders and the Emperor's reinforcements would arrive in mere hours. What happened next is disputed in the Coalition historiography of the Heresy; some believe Horus disabled his Void Shields as he experienced one last moment of regret for his betrayal of his nation and his turn to Chaos, while others believe it was a personal challenge to the Coalition. Nevertheless, Horus lowered the Void Shields of his flagship, the enormous Battle Barge Vengeful Spirit. The lowering of the vessel's shields was detected by the Loyalist vessels nearby and the information was relayed to the Palace.

The Coalition Council rose to the challenge, leading members of their elite personal guard, the Primarchs Sanguinia, Wodin, and Rogal Dorn, and several companies of Imperial Fists, Blood Ravens, and Blood Angels Veteran Space Marines in the assault and teleported aboard the Vengeful Spirit. Horus used his Chaotic powers to scatter the Emperor's force throughout the massive warship when they teleported up through the Warp. Each fought a series of battles against the elite Forces of Chaos aboard the corrupted battleship, attempting to link up with their comrades and confront Horus.

It was Sanguinia who reached her brother Horus first. The Warmaster attempted to turn the Blood Angels' Primarch, his oldest and closest friend among the other Primarchs, to Chaos one last time. When Sanguinia refused to be corrupted, Horus attacked. Wounded from her many battles on Terra and the terrible battle with the demon Ka'bandah, Sanguinia proved to be no match for Horus, now at the peak of his daemonic power after his long alliance with the Ruinous Powers. Horus strangled the Angel of Baal with ease. An alternate version of this event sometimes recorded in the Imperial records has Sanguinius cutting a small hole in Horus' Terminator Armour before she died, as this hole aided in the final defeat of Horus.

When the rest of the forces finally entered the throne room of the Vengeful Spirit, they saw the winged corpse of the angelic Sanguinia lying at Horus' feet. Horus called them foolish for refusing the power that the Chaos Gods offered to Men, particularly at his brother Wodin, and timid for not taming them to their will. Horus proclaimed that if the Concil would kneel before him, then he would spare their life. But the Concil knew well the ancient trap that had snared Horus. And told the corrupted Primarch that he was the deluded slave of Chaos, not its master, for no mortal could ever truly claim to be more than simply a pawn of the Ruinous Powers. Snarling, Horus hurled bolts of daemonic lightning at the Council and soldiers, but the veteran Runelords nullified them with their runic magic. The die was cast. Each side being knew that the fate of humanity now hung in the balance.

The Coalition forces and Horus engaged one another in the throne room of the massive Battle Barge, a battle that was both physical and psychic in nature. Though the combined might of the Coalition were unequaled, they were slowing down from fatigue and injuries, while Wodin found himself unwilling to summon his full strength against his beloved brother. With more of their veteran forces falling at Horus' hands while Wodin suffered grievous wounds at Horus' hands. And after a score of thrusts, parries and counter-thrusts between the Wodin Runesword and his own Lightning Claw, Horus sliced open the Blood Ravens Primarch chest armor, then opened his jugular and severed the tendons in his right wrist, disarming Wodin. A psychic blast seared the flesh from Wodin's face, destroying one of his eyes. After tearing the Wodin's right arm from its socket, Horus raised his brothers broken body high over his head, and broke his back over his knee, causing the remaining forces to back away in terror.

At that moment, a lone Vinci soldier, Ollanius Pious, who had sunk in entered the bridge. Horus showed the Coalition soldier the Primarch's broken form and laughed at the man. The valiant Aio soldier roared and charged the Warmaster, despite knowing he would stand no chance. And was flayed alive by a glancing psychic blast of Chaotic power from Horus.

The casual brutality of the Warmaster's act galvanised Wodin as he realised what awaited Gaiaterra under the rule of Horus and the Chaos Gods. Realising at last that his beloved brother was truly lost to the corruption of Chaos, Wodin finally gathered his full psychic power and unleashed a lance of pure energy that pierced the gloating Horus' defences and ripped his body apart. In some versions of the tale, this blast was only able to pierce Horus' body through the hole that had been made by Sanguinia before her death. Just before Horus died, he looked his brother in the eye, shedding a single tear, begging his brother to forgive him for his betrayal. The Primarch saw regret in his fallen brother's eyes. The Primarch also knew that the Ruinous Powers could attempt to possess Horus again, and that He would not be there to stop his brother again if they did. Driving all of the near-infinite reserves of compassion from his mind for the sake of the humanity he had served and loved all the years of his life, Wodin destroyed Horus utterly, his essence burned from existence in both the physical world and the Immaterium so that the Ruinous Powers could not resurrect Horus as a Demon Prince through their claim on his soul.

The destruction of Horus' soul sent a psychic shockwave surging across Gaiaterra, casting the demons of Chaos back into the Warp, and spreading mass panic among the Traitor Legions and other Traitor forces on the surface of Terra in seconds as the Chaos Gods found their powers disrupted temporarily by the death of their favoured mortal vessel. It became clear to the Forces of Chaos that their leader had been defeated. Retreat turned to rout, and rout soon turned to bloodbath; thousands upon thousands of Chaos Space Marines and Chaos Titans fell attempting to flee. The ground before the Sanctum Imperialis ran red with the blood of Traitors and Heretics.

Meanwhile, the Primarch Rogal Dorn finally found his way to the corrupted starship's bridge, only to discover his fallen sister, Sanguinia, and the shattered body of Wodin, who was on the verge of death, His remaining psychic energy spent in the battle with Horus. It was then that Wodin whispered instructions to Dorn, urging the Imperial Fists' Primarch, his brother, to take make sure that such an atrocity never happened again, before finally succumbing to his wounds.

The Horus Heresy was finally over.

Trivia

 * The Horus Heresy is based on the event of the same name that is the origin of 40k, at least for the imperium. But set to a more modern-ish time and is overall lighter in tone.