Not much is known about Pinwheel, but there are some clues about its nature and goals. This being is seemingly composed of three separated consciousnesses; after noticing the Chosen Undead, the three masks look at each other and twitch lightly as if discussing what to do with the intruder. Its body looks swollen and has three pairs of "arms", hinting that it's composed of three bodies or skeletons fused together. Judging by the amount of tomes and skeletons (all shackled to the ceiling and one on its operating table) inside its lair, we can assume that it isn't hollow and it is doing some kind of necromantic research.
Quick Fireball: fires a quick fire ball
Clensing Fireball: fires a slower, bigger and stronger fireball, has a longer charge up
Flamethrower: breaths a stream of fire
Clone: summons a identical clone of himself, that can mimic pinwheels attack, they die in one hit, and an summon an unlimited amount of clones
Vanish: channels for a while and teleports somewhere nearby