The Clay Thing was an artificial monster created by Madame Tarsa.
The Clay Thing was an artificial guardian, one of the more fearsome toys created by Madame Tarsa to ensure people she banished into the Toymaker's Labyrinth stayed there. Being a lump of Tarsa's already-magical Clay for the Struggling Artist (the last batch of it, in fact) animated by a Life Crystal, the Clay Thing usually sat in its own room of the Labyrinth as an inanimate lump of clay but, when somebody walked in, would shape itself into a replica of them (although speaking only in simple phrases and in a bubbling gurgle) which would then attack the original. If several people faced it at once, it would adopt the form of a hydra-like monster with all of their heads. In 2019, when the Clay Thing was set on Pessimist-242 and Larrikin-1029 by Tarsa, Pessimist-242 flew to their rescue, ramming through the Clay Thing again and again until it managed to destroy its Life Crystal, killing the Thing and causing its clay to vanish into nothingness.
Behind the scenes
The Clay Thing appears as a secondary antagonist in the 2019 short story The Toymaker's Labyrinth.