Battle of Prospero - Council of Nikaea: To end this growing dispute over the use of psychic abilities once and for all, the Emperor summoned the Imperial War Council to the newly terraformed Frontier World of Nikaea to resolve the issue over the use of psychic powers in the Imperium of Man and so that Magnus could rebut the charges of sorcery that had been laid against him.This great conclave, later known to Imperial historitors as the Council of Nikaea, consisted of the primarchs as well as Imperial officials drawn from all the various adepta of the Imperium. From His throne upon a high dais, the Emperor presided over the proceedings on Nikaea in an ancient amphitheatre as each side in the debate made their presentations to Him.The Primarch Mortarion repeated his charge that Magnus employed the use of sorcery whilst Magnus defended his actions and extolled the great deeds achieved by the Librarians and his own Legion's psykers.He also pointed out that the Imperium was already completely reliant on the use of psykers such as astropaths and Navigators for interstellar communication and transportation as evidence to help his cause.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 psychic sorcery.The Emperor's judgement at the Council of Nikaea proved severe. 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.The Emperor commanded that the primarchs were to close their Librarius departments 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 and were ordered to return to their Chapter's battleline.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.Furthermore, Magnus was ordered to return to Prospero to reorganise his Legion, disband the Legion's Librarius and redeploy its existing large corps of Librarians to the Legion's Battle Companies.The Emperor censured his use of psychics and dismissed Magnus with a final threat -- a fate that had also befallen the Lost Primarchs of the II and XI Legions: "If you treat with the Warp, Magnus, I shall visit destruction upon you. And your Legion's name will be struck from the Imperial records for all time."