Not sure what I want to go with yet. Maybe:
The Prepared Adventurer:
"I've seen this kind of psychic mushroom-beast before. We're going to need fire."
Oliver "Dashing" Dashwood was a known and respected adventurer in his day. That day came to a quick end when, during an adventure into the lightless depths of the Underdark, he was set upon and seized by illithids and slated to become one of them through the process called cenomorphosis.
Yet, Oliver was a man who had always believed in being prepared for anything - and was also the luckiest son of a bitch on the face of the planet - and had in his possession an herb that he had discovered himself which the illithid could not abide. By eating the herb himself, the mind flayer tadpole they infested him with weakened and eventually died. Oliver's human mind survived, even as his human body was hideously changed by the tadpole's genetic commands even as it died.
He remained within the mind flayer colony for months, living in fear among one of the most strongly psionic races in the world, before he could realistically fake his death and flee.
Yet illithids are known and despised the world over, and Oliver looked just like them. More, he WAS an illithid in body; he had no choice but to feed the craving for minds once a month, just as a true mind flayer must...
Something like that, anyway. I like factotum characters way more than is healthy.
Alternatively, how do you feel about Dreamscarred Press's 3rd party psionics