what is he, more precisely? a clay golem or a changeling nerfed?

sounds like the original Golem. a creature forged of clay.

A little from column A, a little from column B. A mixture of legends about doppelgangers, golems, and homunculi.

By the way, I'm sorry to shoot down the suggestions about tweaking Face's face, but if I don't set clear rules about what Face's transformation can and can't do, I'm fucked. Face's limitation is that it can only copy, never create, and I realized that I needed to lay that out very clearly.

that's fine, clear rules will help. also if we can get some paintings we can cut them up and mix and match the parts. one guy's eyes someone else's mouth etc etc and it would be able to be copied.