He basically has total control over every molecule of his body- which means he could do horrible, horrible things to people if he really lost it. Remember how he took out the Aztec tank guy in the Obsidian League thing? Imagine that, only with blood vessels instead of machinery. Plas could actually do that thing Neo does to Agent Smith in the Matrix movie. Anybody that needs to breathe? Plas can suffocate them.
And it's not just damage that he can endure. Circe, who's a demi-goddess or something, was unable to successfully polymorph him.