I need help finding a creature to play as a player in D&D 3.5. The idea is that it inserts itself into the brains/head/control center of other creatures. I was not able to find any stats for such a creature, but maybe some of you here on this site can help me. If there is nothing (semi-)official like this, then perhaps you can help me write up some stats for this thing. The current idea is that it has it's own mental stats, and some silly-weak physical stats in its natural form (a very small body?), but uses its host's physical stats when it has taken over a body.
It need not be a psionic creature.