Council of Nikaea - The Debate: 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 xenos 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.These "Librarians" -- so named because they soon became the keepers of their Legion's storehouses of knowledge and history -- 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. Corvus 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 levelled 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 extensive 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 individuals 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, 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.