A Horusian is a member of one of the most extreme of the Radical factions of the Inquisition -- a sub-faction of the Xanthite creed -- that holds that the Arch-traitor Horus might have succeeded in bending the Warp to his will had he not been opposed by his brother Primarchs. Most Horusian Inquisitors carefully hide their true beliefs behind the mask of the more acceptable Xanthite faction and are especially cautious of contact with Thorians.
The First Hour
"You cannot deny Mankind the Emperor, He and the empire He has built are Mankind's only chance of survival."
- — Attributed to Promeus, during a secret conclave of the four founders of the Inquisition, following the Emperor's Ascension
The ideal of restoring the Emperor to the Imperium in mortal form is at the heart of the Inquisition's formation. In the dark days that followed Horus' invasion of Terra and the Emperor's internment in the Golden Throne in the early years of the 31st Millennium, the empire he had created was reeling in the aftermath of the galactic civil war and the Emperor's Ascension. Four individuals, trusted servants of the Emperor during the building of his galactic empire, gathered together to discuss what was to happen. They were divided in opinion, with two believing that the fledgling Imperium of Man could not survive without the Emperor to directly lead humanity, while the other two were adamant that the Emperor had ascended to a higher plane and that it was folly to interfere with the course of events as they had unfolded. The two Resurrectionists, known only as Promeus and Moriana, left Terra to begin their quest of bringing the Emperor back to life, while the two that remained acted quickly to establish themselves within the newly formed Senatorum Imperialis. Known to the surviving Primarchs as loyal servants, these two began to lay the plans for the formation of an organisation that would combat the efforts of the two dissidents. Thus were the seeds of the Inquisition itself sown.
With the backing of the Primarchs, the two first Inquisitors made themselves known to the High Lords and began to recruit like-minded individuals from amongst the Adepts and warriors on Terra. Their dream of an organisation dedicated to the protection of the Emperor would not be realised in their lifetimes, even extended as they were by arcane technologies, and the Inquisition as it is seen today did not fully come in to existence until the 32nd Millennium, by which time the Imperium itself and its many institutions were beginning to grow and spread across the galaxy. Promeus and Moriana were not idle during this time, and in the wake of the news of the Emperor's Ascension gathered together a following of their own, particularly amongst those cults and sects that were now appearing on many worlds claiming the deification of the Emperor. At some point Moriana and Promeus split, their goal still the same but Moriana determined to use whatever means necessary to achieve her aim.
Fearful that Moriana would unleash unspeakable powers of Chaos to achieve her goal, Promeus created a small army of dedicated followers to combat the menace he believed she posed. These two factions clashed many times until Promeus' disciples prevailed and Moriana disappeared, probably into the Eye of Terror. As the Inquisition grew and its presence was felt further and further from Terra, it came into contact with the Promeans. Several hundred standard years had passed since the fateful first conclave, and even then the Inquisition, ever a confederacy of individuals rather than a single body, was pursuing several different agendas. The original intent, to prevent the reincarnation of the Emperor, had been diluted over the centuries, and when the Promeans were discovered fighting against an ill-specified Chaos threat, they were brought into the fold. Neither the Inquisitors that contacted the sect nor the Promeans themselves were aware of the irony of their cooperation, and thus the first Resurrectionist Inquisition faction was created.
The Rise of Horusianism
For nearly a standard millennia the Promeans continued on their quest, combating threats to the Emperor while seeking a means by which He might be brought back to a mortal body. The research of the Promeans rivalled the greatest libraries of the Imperium, but it was dispersed across the galaxy like pieces of a puzzle scattered over a wilderness. By the 33rd Millennium the Inquisition boasted several thousand Inquisitors and hundreds of thousands of Acolytes and other agents, but was still little more than individual bands of dedicated men and women pursuing their own goals, with little or no organisation amongst themselves. Thus were the seeds of heresy allowed to take root once more. It is not known whether Moriana herself was still alive at this point, unnaturally sustained perhaps by the energies of the Eye of Terror, but her legacy was to make itself felt again. Over a period of several centuries, those Inquisitors that had once claimed to be Promeans began to pursue a new philosophy. Amongst the great number of texts compiled over the millennia by their predecessors was a growing body of information concerning musings on the nature of Horus and his possession by Chaos Undivided. Considered by many to be unholy tomes whose secrets were best left forgotten, these texts once more began to be rediscovered and entered circulation and debate.
As the Resurrectionists took greater note of these works, a splinter philosophy began to form, eventually to be dubbed the Horusians. Unwittingly, they were continuing the work of Moriana, investigating the possibility of using the power of Chaos to restore the Emperor to a mortal form fit for His immense psychic presence in the Warp. The nature of their works took them to some of the most uncharted areas of the galaxy, in particular around the Eye of Terror, and unobserved by most they grew in numbers and influence. A few true Promeans still remained, and as they became aware of what was happening, they were horrified. Only a handful had ever read the first teachings of Promeus, or had been recruited by Inquisitors that had seen his works, but they immediately recognised the hand of Moriana in the beliefs of the Horusians. Now a dwindling faction, spread across the Imperium, the few Promeans that remained did what they could to thwart the efforts of the Horusians, but there was little they could do and by the end of the 34th Millennium the Horusians were a dominant part of the Inquisition's agenda.
It was a woman named Stalia von Dressen that stood against the tide. She had been inducted into the Inquisition by a man named Lord Phoran, who had in his possession a second generation copy of Promeus' original works. This had been passed from master to apprentice for nearly two and a half thousand standard years, and the keepers of the book were all dedicated Promeans. Inheriting this mantle, von Dressen was still young and idealistic. Warned by her mentor of the threat posed by the Horusians, von Dressen made it her life's work to combat this menace and see the Horusians' power broken. Abandoning her normal Inquisitorial duties, von Dressen embarked upon a lifetime of travelling, contacting as many of her fellow Inquisitors as was possible. With the Book of Promeus as her guide, she began to recruit to her cause, particularly amongst the oldest and most respected Inquisitors, as well as creating anti-Horusian cells in the worlds that she visited.
Now well-respected amongst the higher circles of the Inquisition, she met Lord Inquisitor Ardlan Baigdan. Between them, they spent two standard decades on Terra itself and using references and clues from the Book of Promeus they found some of the texts created by the original founders of the Inquisition. Though these were truly ancient and terribly incomplete, the two of them pieced together enough information to show them the original schism between the Inquisition and the Promeans. Aged one hundred and twenty Terran years old, von Dressen reached a harsh decision. For her entire life she had been dedicated to the Promean cause, and now had to search deep in her heart to admit that it had been a fool's errand. It is a testament to her conviction that Horusianism had to be stopped that she destroyed her copy of the Book of Promeus and, with Baigdan, initiated a pogrom of pro-resurrection Inquisitors. By the time she died, aged three hundred and four Terran years, this new order was beginning to establish itself and the Horusians were embattled and dwindling. By the start of the 35th Millennium, the Inquisition had turned full circle and Resurrectionism was once again all but eliminated from the Inquisition's goals.
The Horusians At Present
Despite the pogroms of the 35th Millennium, Horusian ideals have waxed and waned in popularity ever since the founding of the Inquisition. The Horusian ideal is quite simple, and yet also unpalatable for many Inquisitors, even those with a fundamentally Resurrectionist outlook. Their assumption is that somehow the powers of Chaos that manifested themselves in Horus might be harnessed for the creation of a Divine Avatar, or perhaps in the process of transferring the Emperor's soul from its current form into the body of a living god. Considered Radicals except by themselves, the Horusians are few in number but fanatical in their cause. They tend to be older Inquisitors, frustrated by the lack of answers provided by other Resurrectionist theories and therein lies the danger. Chaos and its power can never be viewed as a quick route to success, for in that direction lies damnation.
Quite apart from the normal anti-resurrection arguments, many Inquisitors view Horusians with suspicion, out of fear that their dabbling with possession and Warp intrusions endangers those around them and the Imperium in general. However, the most experienced Horusians are well-versed in the perils of the Warp and Chaos and so are numbered amongst the most proficient and dedicated daemon hunters in the entire Inquisition. Like all such philosophies, the Horusians must tread a path along a precipice of dedicated service to the Imperium and the fulfilment of their researches. It is a path that most have trodden wisely, but not all Horusians have remained faithful and, perhaps like Moriana ten thousand standard years ago, succumbed to the lure of the Ruinous Powers.
- Dark Heresy: Core Rulebook (RPG) (2nd Edition), pg. 316
- Dark Heresy: The Radical's Handbook (RPG), pp. 60, 93
- Inquisitor - The Thorians by Gav Thorpe, pp. 3-4, 7