Librarian

The Chapter is continually vigilant to ensure that recruits will not taint the gene-seed of the Chapter through mutation. However, the psyker mutation is often encouraged, and these Marines are inducted into the corps of Librarians. These psychically-charged warriors are trained to use their abilities in the field of battle, as both weapons and tools of precognition. Off the field of battle, the Librarians are responsible for maintaining and adding to the records of the Chapter, attending to the Chapter's annals and the collective knowledge built up over millennia of service. The Librarians use a psychic hood to suppress their enemies' use of psychic powers; the hoods' wires tap into the brain and act as an extension of the wearer's consciousness and allow him to tell when a being taps into the warp. It detects the manipulation of the warp and focuses the Librarian's will to disrupt it through a series of augmentic crystals.

The path to becoming a Librarian is a difficult one, as they must not only be strong enough to survive their training, but possess enough mental discipline to fend off the daemons and entities of the Warp, as these creatures see the enhanced form and mind of a Librarian as a strong prize. Also, the Librarians are often isolated from the rest of the Chapter, as they carry with them the abilities the Space Marines are expected to abhor and purge in all other beings.