Astral Hounds

An Astral Hound is a non-daemonic denizen of the Warp that resembles a large, dark, shadowy dog. Astral Hounds are carnivorous and extremely predatory, but are not intelligent. Brute instinct allows them to track the psychic aura of their prey through Warpspace. Although Hounds can track the psychic aura of any creature with psychic abilities, the strongest and most attractive scent is that of the unprotected human psyker. So strong is their compulsion to seek out the source of this aura that the Astral Hound is the single most dangerous foe of the emergent psyker.

Astral Hounds hunt alone or in packs of up to 6 creatures. They use the psyker's own powers to take form within the material universe. Astral Hounds attack with a numbing bite, paralysing their victim. Once helpless, infortunate victims are taken back into Warpspace, where the Hounds feed upon their psychic energy. The poor psyker simply disappears, confounding friends and neighbours. Astral Hounds are ferocious combat opponents, and are capable of making short Warp jumps of several metres, suddenly appearing behind or beside their enemy.

In other words, they are 40k's version of Hounds of Tindalos.