pteroThe Slime Butler
In-world: a couple of these weird constructs are the only companions of a massively depressed Beholder.
It is roughly the size and shape of an adult human, and indeed contains a full skeleton of what look like mostly human bones. Bound to this skeleton, and held in fairly rigid form somehow, is an as of yet unidentified electrostatic ooze. It looks like a lava lamp full of bones that can walk, essentially.