Realm of Chaos: Slaves to Darkness (1988), p240-243 — The Traitor Legions

The Eye of Terror is a region of space cut off by warpstorms, wreathed in dust clouds, cloaked in mystery and danger. While it lies inside Imperial Space, it is not part of the Imperium. It is a desolate volume of space - the small number of systems to be found within the Eye have few habitable planets. However, its isolation from the Imperium is due to another cause. The Eye of Terror is home to the Imperium's oldest enemies and greatest rebels: the Traitor Legions.

Banished from the Imperium, the Traitor Legions are the remnants of nine Marine Chapters from the First Founding. Deep inside the Eye, beyond the range of even the most sensitive psyker, the Traitor Legions made planetfall. There they have remained to the current day, a threat to the Imperium and to the natural order of the universe. From their fastness within the Eye of Terror, the Traitor Legions emerge in force, falling upon Imperial worlds, rekindling the fear and despair of the Horus Heresy.

The Horus Heresy

Imperial entanglements with Chaos have a long and bloody history, dating back almost to the First Founding of the Legiones Astartes. The most serious incident was the so-called Horus Heresy of the 31st Millennium, now commonly assumed to be a conventional revolt. Only the Emperor and the Cyber-libraries of the Ordo Malleus have an accurate recollection of the Heresy.

General Horus was regarded as the finest military commander that the Imperium had produced. His abilities were faultless, and eventually the Emperor granted him the title of Imperial Warmaster. This was a high honour, even in the early years of the Imperium, when brave deeds were commonplace.

Before Horus could travel to Terra to receive his reward he fell ill on the feral world of Davin. This was his undoing. During his convalescence on Davin he was inducted into a secret warrior's lodge, which proved to be little more than a coven. A change of character became evident in the Warmaster - he had been possessed by a Daemon. Horus' membership of the secret lodge was not unusual; Imperial solders were often encouraged to join warrior societies of this type. Recruiting was felt to be easier on worlds were 'warriors from the stars' had become 'brothers'.

Warmaster Horus was recalled to duty in preparation for a new Imperial Crusade. It is clear that the Warmaster introduced a system of 'warrior lodges' into the five Legiones Astartes Chapters under his direct command. The Chapters were entirely corrupted as the lodges revealed their true nature and showed themselves to be nothing less than Chaos covens. The infection rapidly spred to the Orders of Adeptus Mechanicus attached to Horus' command. From there the rot spread further into the Imperial forces. More than half of the Adeptus Mechanicus, including many units of Collegia Titanica and the Legio Cybernetica wholeheartedly supported Horus and his vision of a new Imperium of Chaos. This wholesale treachery went undetected by the Inquisition.

Before Horus could move, the Imperial Commander of Isstvan III declared the entire Isstvan system to be an independent principality. The Emperor and Administratum, ignorant of the change in Horus, his subordinate chapters and the parts of the Adeptus Mechanicus, ordered the Warmaster to secure the system. Horus chose a bioweapon combardment on Isstvan III, and the planet became a tomb in seconds. The psychic death scream of the 12 billion who died during the Scourging of Isstvan is reputed to have been louder than the Astronomican.

During the bombardment, loyal Adeptus Astartes officers and troops managed to seize control of the frigate Eisenstein. They had discovered the rot that had been spread through the Warmaster's Chapters and the Adeptus Mechanicus. As Horus completed his withdrawal to Isstvan V the loyalists fled into warp space, carrying a warning to the rest of the Imperium. The seizure of the Eisenstein is regarded as the start of the First Inter-Legionary War.

The Emperor now became aware of the danger, and the Inquisition began a purge of the Adeptus Mechanicus. Fighting broke out immediately as the Mechanicus split into loyalists and rebels. The Legio Cybernetica and Collegia Titanica bases on Mars were immediately besieged by loyalist troops. Out of all the Titan Legions of the Divisio Militaris only those on Terra remained loyal. The rest declared for Horus.

With the wholesale treachery of the Divisio Militaris, the loyalist faction within the Collegia Titanica was forced to husband its battlefield resources. Fortunately, many of the weapon shops and supply depots of the Collegia had remained loyal. The priesthood were in control of the Collegia depots, and their presence ensured that these vital resources remained in the hands of the Imperium. The rebels were presented with an immediate supply problem; damaged and destroyed Titans could not be repaired with the limited spares stockpiles held by individual Orders.

Savage battles broke out between loyalist and rebel Titan Orders. Faced with extinction through lack of spares if they delayed or acted defensively, the rebels attacked. The Collegia histories list many construction adepts who performed the dedication rites on a new Titan, and then mounted their charge and took it straight into battle. In some cases the libations were still wet when it reached combat. Only able to match such fanaticism with their sheer weight of numbers, the rebels were often forced into a position of stalemate. However, despite the valiant defence of these loyal remnants of the Collegia Titanics, enough supplies were captured to allow the rebels to make good use of their Titans during the final assault upon Earth.

Across the Imperium rebel units attacked loyalists and vice versa. Old feuds were revived in many systems, giving additional excuses for battle. The rule of the Imperium dissolved into planetary battles. Many units of the Imperial Guard declared for the Warmaster. The Imperial Fleet dithered and managed only to drive rebel ships from the Imperial home system. In the process they took heavy casualties and retired to their Luna bases.

The Emperor took stock of the situation, and ordered seven entire Marine Chapters, a third of the Legiones Astartes to destroy Horus and his rebels. Only with the death of the Warmaster, the figurehead and inspiration of rebellion, would the revolt come to an end. The crusade against Horus, although of the utmost urgency, took more than 180 days to plan and launch. Horus used the time well, establishing his claim as a 'New Emperor' with many of the rebels, and spreading the worship of Chaos further afield.

The Warmaster had established a temporary headquarters on Isstvan V. The loyalist Chapters struck in quick succession, and the battles of the Pacification of Isstvan were bloody in the extreme. The first assaults by loyalist Chapters were mauled during their landings, and then destroyed in detail. Three complete Chapters took part in the initial landings on Isstvan; only five Marines, bearing the gene-seed of their departed brothers, eventually managed to escape to carry the news of the disaster to the Emperor. Their own 'loyalist' follow-up waves, rather than attacking the rebels, fell upon their erstwhile allies. Horus had, apparently, managed to corrupt four of the seven Chapters sent against him.

With nine rebel Chapters and the bulk of the Adeptus Mechanicus behind them, and three loyal Chapters destroyed, Horus assaulted Earth. Throughout the Imperium rebel and loyalist units were fighting each other to a virtual standstill, although the tide of battle was turning, ever so slowly, in the Emperor's favour. Possessed as he was, the Warmaster had lost none of his strategic bluntness: crush the heart, and the Imperium could be remoulded in his own warped image.

The Imperial Fleet was bypassed, and its Luna bases destroyed. Within 30 standard days the Warmaster had reduced the system defences, infested Earth, and thrown a ring of troops about the Imperial Palace. The forces under Horus' command had ceased to be loyal Imperial Marines. They had become the Traitor Legions.

The Adeptus Custodes, the Imperial Fist and Whitescar Chapters, and loyalists of the Collegia Titanica were all that remained on Earth. Even their suicidal bravery and the leadership of the Emperor were not enough to prevent the battle turning into a siege. The rebel Traitor Legions were aided by the machines of the Adeptus Mechanicus and, outnumbered by these, even the bravest loyalists could do little. By the 55th day the Traitor Legions and the rebel Adeptus Mechanicus Legions had reached the walls of the Inner Palace.

The situation grew more desperate by the hour and, when the Outer Palace was abandoned to the Traitor Legions and their allies, the Emperor acted. He disconnected himself from the Astronomican, a signal to the remainder of the Imperial Fleet that the end, one way or another, was approaching. The Emperor and an elite company of Custodes Adeptus soldiery and Imperial Fist Marines were then teleported into Horus' command bunker. In the fierce fighting that followed Horus was killed (although his body was never found), and the Emperor seriously wounded.

With the death of the Warmaster the rebels paused in their assaults, then fell back to their transports and fled into space. The Imperial Fleet, which had been powerless to intervene while the rebels were within the Palace, gave chase. The Emperor returned to the Palace, where he was placed within a life-bubble; his wounds would have been fatal for an ordinary man. Under his watchful eyes the construction of the Golden Throne, which sustains him to this day, began.

His future assured, the Emperor pronounced judgement on Horus and his Legions. They had broken faith with the Emperor and trafficked with Daemons. They were declared to be the Traitor Legions, rebels against the Emperor and Mankind. The Fleet was ordered to drive them into the Eye of Terror, a system of hell-worlds wrapped in a dust nebula and awash with warpstorms. Here the Traitor Legions would be confined for all eternity; all records and memories of the lapsed Marine Chapters would be expunged from Imperial Archives. Their tied servants and support troops were to be removed from the Isstvan and Davin systems, and sent into the Eye aboard almost derelict hulks. It would be as if the Traitor Legions had never existed. In this decision the Emperor tempered his vengeance with reality - the Imperium had been so weakened by the struggle that no other punishment was possible.

As news of the Warmaster's defeat spread through the Imperium widespread fighting was renewed. The loyalists were revitalized by the news, and fell on the rebels. Many Guard and Fleet detachments had withheld their support from both sides. Such indecision was punished by the rebels and loyalists alike. The loyalists bled such formations white in attacks against rebel strongholds. The rebels turned on all within reach in a final despairing orgy of destruction. The fighting continued for another seven years before the last rebel formations were destroyed or exiled.

Those who could flee did so, heading for the Eye of Terror. Many had declared for the Warmaster without understanding that Daemon-worship had been the rebellion's cause. They rapidly fell victim to the cultists of the original Traitor Legions, who, it is said, grew bored of a diet of human flesh.

The destroyed Chapters were slowly re-restablished using what gene-seed had been saved. Many systems, including Davin and Isstvan, were cleansed and placed under the protection of the Inquisition. The unit designation of the Traitor Legions were placed on the inactive list and assigned to new Marine Chapters raised during later Foundings.

The Emperor's body had breathed its last, and he entered the Golden Throne. The Traitor Legions and their dead Warmaster vanished into the Eye of Terror. The First Inter-Legionary Way - the Horus Heresy - lasted less than a decade, but it nearly destroyed the Imperium.