Librarian

Every Chapter that trains psykers does so with tremendous caution, for the same warp-touched gift that lets a Librarian hurl bolts of psychic force or shield his brothers from harm is the exact vulnerability that daemons and sorcerers exploit to unmake a soul from within. Candidates are drawn from Battle-Brothers who manifest psychic potential, and their training within a Chapter's Librarius is as much about building unbreakable mental discipline as it is about mastering any specific power.

Once fully trained, a Librarian becomes an invaluable battlefield asset, capable of shielding a squad from incoming fire with a barrier of raw force, scouring an enemy's mind for tactical secrets, or simply unleashing devastating psychic annihilation on a hardened position. Many also serve their Chapter as scholars and keepers of forbidden lore, since a mind already trained to withstand the warp's corrupting whispers is uniquely suited to study the heretical texts and xenos artifacts that would drive a lesser scholar to madness or worse.