Astartes Psykers

The aspirants and newly-implanted neophytes of all Space Marine Chapters are screened by the Chapter's Librarians for signs of psychic capability. Those who possess the potential to become a Librarian are then forced to undergo the same trials and sufferings all other Space Marine neophytes of their Chapter face, but they also have to learn to harness their powers and protect their minds from the daemonic dangers of the Warp.

As Space Marines are far stronger mentally and physically than an ordinary man, their flesh is ideal for Daemons to inhabit as a daemonhost. For a Librarian, each day is a long walk along a narrow path which, should they stumble or stray, leads only to madness, possession and the deaths or destruction of all that they hold dear.

The training within a Chapter to become a Librarian is very difficult, as new Librarians must not only be strong enough to survive the rigours of 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 great prize through which they could work much evil in the physical universe.