Astral searcher

Astral searchers are the bane of planar travelers in the Astral Plane. They are mindless shells of nebulous humanoid shape, created by concentrated or traumatized thoughts of prime-material characters in the silvery void. Violent death, destructive spells cast while on the Astral Plane, and astral combat often result in the creation of astral searchers. More often than not, the creator or source of the astral searcher isn't even aware of the results of his or her actions, and this creature comes into being without malice of forethought or other intent.

Driven by their past connection with material beings, astral searchers obsessively search for material bodies to possess. As they wander the Astral Plane, they seek weak points in the cosmic fabric that connects the Astral to the other planes, and they cluster at those points, waiting for the stress lines to become collinear so that they can pass into other worlds. Such "rips" in the planar tapestry exist naturally, but they also may be created at points where astral travelers enter and leave the Astral Plane, in which case they exist only temporarily. Astral searchers also gather near the color pools that lead to the Prime Material and Outer Planes, but they are incapable of passing through them unless a planar being passes through before them.

Note: Astral searchers originally appeared in this form in the Planescape AD&D campaign setting from TSR. Its use here is for the purposes of providing context for the campaign only.