Dating a librarian
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.We must master this gift, make a weapon of it, lest we be consumed by its fury." 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.A Librarian faces a thousand enemies before he even goes to war –- to the creatures of the Warp, his mind is a choice prize.Each day is a walk along a precipice, and a false step can see him tumble into madness.Librarians are the psykers of the Space Marines who survive an Adeptus Astartes Chapter's rigorous screening and training to bend the powers of the Warp to their will for the benefit of their fellow Battle-Brothers and in service to the Emperor of Mankind.Beyond their psychic duties, the Librarians of the Astartes are also expected to record the great deeds of their Chapter and maintain the Chapter's storehouse of ancient lore, the functions for which they are named.
Apothecaries rigorously screen potential recruits for any sign of genetic deviation, but not all mutation is physical.If a recruit survives the rigorous testing, he joins the Librarius as a Lexicanium, rising through the ranks to become Codicier, Epistolary or perhaps even the Chapter's Chief Librarian.He will use his abilities to pierce the Warp and provide the means for interstellar communication, as well as to identify others of his own kind.Space Marine Librarians use their abilities to serve the various undertakings of their Chapter; however, their actual place in the order of battle is always with the Librarium in a Codex Astartes-compliant Chapter.
As the name suggests, the Librarium is a place within a Space Marine Chapter's fortress-monastery where the Chapter's vast knowledge base, gathered over millennia of hard-fought battles and participation in engagements the length and breadth of the galaxy, is stored.
A Librarian is often estranged from the other members of his Chapter.