Had an idea for a guy whose ability is Insanity Inducement. Might make a good villain or a creepy ass hero.

Basically his only weaknesses would be fire, large bodies of water or targeted electricity since his physical form is actually a swarm under the guidance of a single consciousness that can secrete a gas that cause hallucinations that are guided by him to bring about insanity.
He'd be like a swarm of termites or flesh-eating insects, devouring almost anything (wood, people, ice, glass) to feed himself and add to his swam with any excess mass being represented by clothes, items like canes or swords or an ever present swam of insects that are constantly flying around him or crawling over him. Whenever he enters a room he would cause any electrical lights to fail and he could appear as a formless, inky cloud. If part of his swarm were to be destroyed, he would merely need to consume something to rapidly breed or produce replacements, like a swarm of nanites but organic.