Librarian - History: The Imperial records concerning the origins of the Space Marine Librarians are murky and mired in legend rather than hard facts like much of the history of the Imperium's early days. However, according to the chronicler Saphrus the Ancient, during the Great Crusade of the early 31st Millennium the Emperor of Mankind held a great Imperial conclave, the Council of Nikaea, on the newly-terraformed planet of the same name, to determine whether human psychic powers and the practice of psychic sorcery presented a danger to the newborn Imperium of Man and its people.Within the Imperium there were those, like the Thousand Sons Space Marines Legion of the Primarch Magnus the Red, himself a powerful psyker, who had an extremely high rate of psychic mutation and regularly used psychic abilities and sorcery to expand the growing Imperium's reach across the galaxy. Others, such as the Space Wolves Legion of the Primarch Leman Russ and the Witch Hunters known as the Sisters of Silence, held that all psykers, even those who were Astartes like the Thousand Sons, represented a grave threat to the human race.Some Primarchs had accepted the ideas of Magnus on the beneficial use of psychic abilities in their own Legions, while others like Leman Russ refused to deal with what they saw as dishonourable deception and unnatural witchery and outlawed all psychic powers as simply sorcery by another name.The Emperor invited the advocates of both sides to attend the conclave and at the Council on Nikaea they argued each other to a standstill. It was only the intervention of a contingent of Space Marine Librarians from the other Legions besides the Thousand Sons that presented a compromise.Their proposal was that while the Imperial education of psykers to best serve humanity should be made a priority, the conduct of psychic sorcery would be outlawed as an unforgivable heresy, since psykers were simply tools who could serve Mankind for good or ill, but the powers of sorcery could only be gained by treating with the foul denizens of the Warp whose malevolent intentions were often manifest.This compromise was rejected by the Emperor once it was revealed that Magnus the Red had continued to explore the power of sorcery after the Emperor had warned him of its dangers solar decades before. The Emperor disregarded the proposed compromise and ordered all of the Space Marine Legions to disband their Librarius corps and for Astartes Librarians to return to service as line warriors and never use their psychic abilities again. Unfortunately, after the outbreak of the Horus Heresy, it became clear that the Forces of Chaos could not be defeated unless the Loyalists were also able to draw upon the power of the Warp.Following the end of the Heresy, the original compromise proposed at Nikaea was adopted as law without a provision for rebuttal, and it has stood for ten thousand standard years as the official policy of the Imperium on the use of psychic powers. Today, in the 41st Millennium, each Chapter remains vigilant to ensure that new recruits will not taint the gene-seed of the Chapter through mutation. However, the psyker mutation is often encouraged, and these Astartes are then inducted into the Chapter's corps of Librarians.