Enslavers (Warhammer 40,000)

The Enslavers are a race of beings from Immaterium which control any being that they can in order to turn them into Living Warp Portals that more enslavers can enter the material universe through. This control appers to be psionic in nature. The enslaver plague forced the C'tan to hide from them, as psionics (and the warp itself) are lethal to them.