Astral Spectres are warp creatures formed from psychic energy and the fabric of the Empyrean, and created by the foolhardy actions of an untrained psyker. They feed off soul-essence, requiring a constant supply of warp energy to survive.
Spectres vary in appearance, but all retain the same basic form. Each is a vaguely humanoid figure, composed of semi-translucent shadow. They are uniformly vile and horrifying to behold, and their mere presence unnerves nearby creatures.
While the natural form of a Spectre is incorporeal, they are able to possess the bodies of intelligent beings. They feed off the soul of their host, leaving them as a mindless husk, and absorb some of their host's memories, which the Spectre uses to maintain a façade of normality.