Librarian - The Librarius: At the centre of a Chapter's fortress-monastery there usually lies a vast sealed chamber known as the Librarius, also called the Librarium, that is filled from floor to ceiling with books, scrolls, and data crystals. Overseen by the Chief Librarian and maintained by lexicaniums and codiciers (supported by a small army of servitors and Chapter serf scribes who work ceaselessly), the Librarius is the repository of all the Chapter's knowledge and history.Even within the Chapter, few are given access to this chamber and fewer still have the chance to study its texts. Even the most well-read Imperial scholar or Administratum adept can only guess at the secrets and lore contained within one of the fabled Space Marine Librariums.This repository is a wealth of knowledge that the Chapter Master guards well, knowing that in times of need he may have to call upon the counsel of his Librarians and the lore they possess to guide him in battle.In the heart of the Librarius there is also a smaller inner chamber, carefully sealed and protected. This is where the Chapter stores its most sacred artefacts, trophies, and proscribed texts, many of which are taken from the corpses of Heretics and aliens -- unfit or too dangerous for the eyes of any but the Chief Librarian.It is often a point of friction between the Ecclesiarchy and the Adeptus Astartes that its Chapters possess such items or take them from their foes in battle. Of course, not even the most reckless Imperial cardinal would dare consider confronting any Space Marine Chapter over this matter.When not devastating the plans of enemy warlords in war zones from the Damocles Gulf to the Cadian Gate, Librarians have a host of other, less violent, duties to attend to. In addition to testing new recruits for psychic ability and tending to their own training, Librarians are responsible for maintaining their Chapter's Librariums.Overseen by the Librarians, each is a silent and sacred place of whispered secrets and hidden truths. Filled with ancient tomes and sacred scrolls, every piece of text laid down by the Chapter, or relevant to its existence, is housed within.Every fortress-monastery will have a Librarius to house the lore, battle records, and certain psychically-active artefacts like Force Weapons. Famous victories, shameful defeats and the legends of the Chapter's heroes are recorded there, and the Librarians are fiercely devoted to their role as keepers of their legacy.In addition to the main Librarius on a Chapter planet, many battle barges maintain smaller Librariums for use during their long campaigns. While no two Librariums are exactly the same, they are often built around a central pillar, its racks of books and scrolls spiralling out into antechambers that hold rows of written works, data-slates, chronicle-stones and mnemo-slates recording the accounts of great battles, the final words of its heroes, and the secrets of vanquished foes.The central pillar of most Librariums houses its oldest available copy of the Codex Astartes, held in a stasis-plinth or protected by holo-reflection.Many lords of the Adeptus Astartes visit the quiet, dusty halls of the Librarius to draw their inspiration and resolve from that ancient book in times of darkness.