Psykers are among the most powerful beings in Warhammer 40K, possessing psychic abilities that let them manipulate the Immaterium of the Warp to their whims. However, unlike traditional spellcasters, the alien nature of the Warp has the risk of corrupting its wielders. The weakest of Warhammer 40K Psykers either die in their attempts to cast their spells, or their bodies become conduits for the Ruinous Powers.