Nikaea is a Frontier World widely known in Imperial history as the site of the Council of Nikaea where the Emperor of Mankind and his Primarchs met during the Great Crusade to decide the fate of mutant human psykers and the use of particularly potent psychic powers or "sorcery" within the Imperium of Man.
Ultimately the existence of certain psykers in the Imperium like Navigators and Astropaths was allowed but tightly restricted under centralised Imperial control, while combat psykers and the unrestricted use of psychic abilities to treat with the entities within the Warp that was defined as sorcery were officially banned.
The world had been newly discovered by the Imperium at the time the Council was convened and the Emperor had ordered the Mechanicum to terraform the planet and make it habitable for humanity so that it could host the great Imperial conclave and then be settled afterwards. The psychically powerful Primarch Magnus the Red and his Space Marine Legion the Thousand Sons would continue to study such powers in secret on their homeworld of Prospero, ultimately leading to their damnation by Chaos during the early days of the Horus Heresy.
Council of Nikaea
The Council of Nikaea was a great Imperial conclave called by the Emperor of Mankind during the early 31st Millennium on the world of Nikaea in the midst of the Great Crusade that was intended to determine whether or not the use of psychic abilities represented a boon or a grave danger to Mankind and the newborn Imperium of Man.
More and more often during the progress of the Imperial conquest of the galaxy, the Imperial Army and Space Marines would make planetfall only to find that the populace were in thrall to mysterious powers. These people were essentially members of Chaos Cults who would resist the forces of the Emperor with sorcerous powers granted them by daemonic beings from across the Warp. These powers were also very akin to those used by the Thousand Sons Legion of the Primarch Magnus the Red. The Thousand Sons had come under criticism for their use of sorcery by the Primarch Mortarion of the Death Guard Legion, who knew by his own personal experience with sorcerers on his homeworld of Barbarus the dangers to be found in anything spawned from the Warp, and Leman Russ of the Space Wolves Legion, for whom any battle fought through sleight of hand, clever deceit or any trick other than straight physical combat was by definition dishonourable.
Russ found the Thousand Sons' use of sorcery distasteful in the extreme and it was Russ who had fought the hardest for the Imperium to ban the use of psychic powers after his own experiences during several campaigns of the Great Crusade where his Space Wolves had fought beside the Thousand Sons. The schism grew so great that it threatened the very stability of the fledgling Imperium and so the Emperor himself had called for an Imperial conclave to resolve the issue once and for all.
There was an increasing concern as the Great Crusade progressed about the use of psychic abilities. The Emperor was of course the most powerful human psyker to have ever lived, but he was deeply ambivalent about the spread of the mutant psyker genes through more and more of the human population, as he rightly believed that most of Mankind was not yet evolved enough either physically or spiritually to truly control the great power of the Warp or avoid the temptations offered by its more malevolent denizens.
More and more often during the progress of the Imperial conquest of the galaxy, the Imperial Army and Space Marines would make planetfall only to find that the populace were in thrall to mysterious powers and unnatural mystics and so-called "sorcerers." These people were essentially members of Chaos Cults who would resist the forces of the Emperor with sorcerous powers granted them by daemonic entities from the Warp.
These powers were also very akin to those used by the Thousand Sons Legion of the Primarch Magnus the Red. The Thousand Sons had come under criticism for their use of sorcery by the Primarch Mortarion of the Death Guard Legion, who knew by his own personal experience with sorcerers on his homeworld of Barbarus the dangers to be found in anything spawned from the Warp, and Leman Russ of the Space Wolves Legion, for whom any battle fought through sleight of hand, clever deceit or any trick other than straight physical combat was by definition dishonourable. Russ found the Thousand Sons' use of sorcery distasteful in the extreme and it was Russ who had fought the hardest for the Imperium to ban the use of psychic powers after his own experiences during several campaigns of the Great Crusade where his Space Wolves had fought beside the Thousand Sons. The schism grew so great that it threatened the very stability of the fledgling Imperium and so the Emperor himself had called for an Imperial conclave to resolve the issue once and for all.
Unlike his brother Primarchs, Magnus the Red saw the potential in exploiting the powers of psychically talented Astartes and he had been instrumental in the development of the Space Marines' corps of Librarians. In some of the Astartes Legions the psychic mutation was relatively common and it was felt by some of the Primarchs that such individuals should be allowed to continue to use their innate psychic abilities for the benefit of the Legion. This would allow these gifted Battle-Brothers to be of use to their Legion without presenting any danger to their fellows or to the civilians of the Imperium. Magnus and a number of other Primarchs created a program for the training and development of psyker Astartes that supplemented the traditional process for creating a new Space Marine. The Emperor was asked to approve of the recruitment of these psykers into the ranks of those Legions who wished to make use of them, and he sanctioned these first experiments as a means of controlling the spontaneous outbreaks of psychic mutation within the ranks of the Legions. The Librarians quickly proved to be loyal and effective warriors and soon gained acceptance by the Emperor and the Primarchs for their presence on the battlefield. The Librarians became a powerful addition to the ranks of the Space Marine Legions.
However, there were those Primarchs who raised their voices in dissent, arguing amongst themselves and with the Emperor that Librarians should not be permitted within the ranks of the Astartes. Some desired to expand their Legions' Librarius and recruit even more Librarians into their ranks, whilst other Primarchs vehemently opposed the entire notion of Librarians and felt that they should be expunged from their ranks altogether. Primarchs such as Leman Russ felt that Librarians were no better than witches. Corax and Rogal Dorn also refused to commit their Legions to fight alongside other Legions that made use of Librarians. Mortarion in particular accused his brother Magnus of using the forbidden arts of sorcery.
Dismayed at the accusations leveled against Magnus and the friction the issue was causing amongst his Primarchs, the Emperor was also concerned about the Librarians and the dangers they presented to the Great Crusade when he was no longer fighting directly alongside his Space Marine Legions. Before departing for Terra to begin his secret Imperial Webway Project within the seclusion of the Imperial Palace's dungeons, he summoned the Primarchs and all the other major Imperial leaders to a War Council summit on the world of Nikaea to address the Librarian crisis.
Both sides of the debate over the use of psychic abilities arrived at the world of Nikaea determined to present their views, with the Emperor as the arbiter, enthroned above the dais in an ancient amphitheater that seated tens of thousands where the conclave was held. On one side of the question were the Witch Hunters like the Sisters of Silence who presented their case by reciting a litany of the human suffering inflicted upon the Emperor's own subjects by sorcerers enslaved by what would later be recognised during the Horus Heresy as Chaos, of gibbering mutants who had lost their humanity, and of cults and power-hungry men who turned their psychic gifts to dark purposes.
All present were also aware of the terrible damage that had been done by uncontrolled and daemon-possessed psykers during the early days of the Age of Strife. On the other side was a powerful advocate for the continued use of sorcery, the Primarch Magnus the Red. His very presence frightened many, but he began to speak with the great charisma that only a Primarch could wield. His argument was that no knowledge was tainted in and of itself, and no pursuit of knowledge was ever wrong so long as the seeker of that truth was the master of what he learned rather than its pawn.
He spoke with finality that his Thousand Sons Astartes had mastered their knowledge of sorcery and that there was no knowledge too labyrinthine for them to grasp or that they could not master to serve Mankind rather than enslaving it. Magnus called on the Emperor not to ban the use of psychic abilities, but to contribute to further research into their usage so that they might be harnessed more fully for the betterment of humanity and the Imperium.
Edicts of Nikaea
Magnus had spoken passionately with great power and the Council became even more divided. While they had strong arguments in their favour to justify their anti-psyker position, the Witch Hunters could not effectively match Magnus' persuasiveness. The tension could easily have been cut with a knife when a group of Space Marine Librarians approached the dais.
The Emperor acknowledged them with a nod, and all present fell silent. Among the group were some of the greatest Librarians of the Space Marine Legions. They formed a semi-circle around the dais to indicate that they spoke as one voice, but it was a young Librarian Epistolary who spoke for the group. A psyker, he proposed, was like an athlete, a gifted individual whose native talent must be carefully nurtured. Psykers were not innately evil in themselves, but like any tool, could be used for either good or evil purposes.
Sorcery, however, was a knowledge of how to wield psychic powers that had to be sought for, even bargained for with the foul entities of the Warp. No one could be truly sure who or what had benefited in the deal. The Librarians proposed that all psykers be strictly educated by the Imperium with the express purpose of using their abilities to serve Mankind. This should become an immediate Imperial priority. The practice of psychic sorcery would forever be outlawed as an unforgivable offence against Mankind and the worst kind of heresy. The end result of the Council of Nikaea's deliberations was ultimately a compromise that offered both the pro-and-anti-psyker factions something.
The Council of Nikaea was also the trial of Magnus the Red -- for he was accused of sorcery and of introducing sorcerous practices to the Space Marine Legions through the institution of the corps of Librarians. As the evidence of Magnus' continued practice of sorcery became apparent, the Emperor barely contained His wrath as He pronounced judgement on the Primarch of the Thousand Sons, for He had entrusted His son years before to obey his bidding and foreswear the use of such occult practices because of the dangers inherent to the Warp.
He had entrusted only Magnus with the true secrets of the Warp to which only they remained privy, but now it appeared that His son had disobeyed his edicts and at the very least dabbled in the occult and the forbidden black arts of sorcery by repeatedly treating with the denizens of the Warp. The confrontation between father and son is recorded in the Grimoire Hereticus.
The Emperor's judgement at the Council of Nikaea proved severe, largely as a result of his anger at Magnus. The Emperor rejected the Librarians' compromise. With the exceptions of Navigators and Astropaths who were properly trained, controlled and sanctioned by the Imperium and were necessary to its continued existence, the Space Marine Legions were no longer to employ psykers within their ranks. He commanded that the Primarchs were to close their Librarius departments forthwith and not to indulge the undoubted psychic talents of those Asartes who possessed the gift. All existing Space Marine Librarians were likewise forbidden to make use of their abilities. The Council's rulings also created a new position amongst the Space Marine Legions, the Space Marine Chaplain, to uphold the Imperial Truth and help maintain the purity of an Astartes Legion's dedication and fidelity to the Emperor's commands.
The Emperor ordered Magnus to cease the practice of sorcery and incantation immediately, and the pursuit of all knowledge related to magic. Magnus, of course, did not like the idea, and he remained bitterly opposed to the decision made at Nikaea. But in the end, he bent his will to his father the Emperor and agreed to obey, though the machinations of the Ruinous Powers would ultimately lead to a far darker fate for Magnus the Red and his Thousand Sons.
The Edicts of Nikaea stood largely for the next 10,000 standard years as the primary Imperial policy regarding human psychic mutation. Only the edict against the use of Librarians within the ranks of the Space Marines and of combat pyskers in the wider Imperial military forces would be reversed as a result of the Horus Heresy, as that terrible civil war made clear to the rulers of the Imperium that combat psykers were essential to face the fell powers of the Forces of Chaos.
The term "Council of Nikaea" is an historical reference to the Christian Church's Council of Nicaea, which occurred in the year 325 AD in the Roman Empire's province of Asia (Asia Minor) and was hosted by the Emperor Constantine the Great. This Council of Nicaea determined the content of orthodox Christian belief as laid out in the Nicene Creed of the Roman Catholic, Protestant and Eastern Orthodox Churches.