The ustilagor appeared in the second edition of Advanced Dungeons & Dragons under the "intellect devourer" entry in The Complete Psionics Handbook (1991), and reprinted in the Monstrous Manual (1993).
A ustilagor is a small creature that appears to be a brain-like fungal growth with coral-like appendages. Although soft and not fast by normal standards, a ustilagor can scuttle and dart about. Its attack consists of flicking out a 3-foot long, ribbon-like tendril coated in caustic alkaline fluids. A ustilagor has no intelligence or mind by human standards, but it does have some form of brain because it has psionic powers.