Seriously, they are highly magical and their spells are highly potent. And by highly potent I mean, might release all their magical energy by accident or intent killing everyone in the room, and maybe even surrounding rooms. They have the ability to heal anything and anyone with full power as soon as they are spawned.
They're no good with most weapons other than scissors and blunt instruments, in particular large mallets. They also can deliver a mean punch and kick. They also have the ability to ram others.
Their compulsive behaviors are scripted automatic responses to various things. For example, if someone mentions masturbation or anything sexual, certain variants of Fae will bonk the offender over the head, or perhaps offer it lube, or if its one of the really crazy ones, follow its target around for some number of ticks attempting castration with scissors. Playing one of these characters would be rather interesting, although most will be NPCs.
There's a 1:10,000 chance of rolling a Fae character. Its magic number 7227.