Council of Nikaea - Edicts of Nikaea: Magnus had spoken passionately with great power and the Council of Nikaea 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 against the Imperial Truth.Yet 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 many Terran 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 and the existence of the terrible entities later known by Humanity as the Chaos Gods to which only they remained privy, but now it appeared that His gene-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.As a result, 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' proposed compromise between the practice of restrained combat psyker abilities and the pursuit of true sorcery. 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 Emperor decreed that the Space Marine Legions were no longer to employ combat psykers within their ranks.He commanded that the primarchs were to close the Librarius departments of their Legions forthwith and not to indulge the undoubted psychic talents of those Astartes who possessed the gift. All existing Space Marine Librarians were likewise forbidden to make use of their abilities. The Council of Nikaea's rulings also created a new position amongst the Space Marine Legions, the Space Marine Chaplain, drawn from the practices of the Word Bearers Legion, 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. In this way, the Librarians' original compromise that the Emperor rejected at Nikaea eventually became the Imperium's de facto policy concerning psykers in the wake of the Horus Heresy.In the 41st Millennium, the choice of whether to make use of Librarians was left to each Chapter of the Adeptus Astartes to decide for itself. For instance, the Salamanders explained to their rivals the Marines Malevolent that they felt the strictures of Nikea were outdated and psychic powers should be cultivated more assiduously, while the Marines Malevolent and many other Chapters retained a healthy distrust of psykers and all those who dealt with the Immaterium.