Snakes for hair? That kind of gives it away, doesn't it? I mean, the ONLY thing in the world with "snakes for hair" is the medusa.

I mean, without that, the answer could also be basilisk (Using only final fantasy, we could also be talking Eye, Phantom, Cocatrice etc...) - Which, if you could add in something else to be more specific yet also more difficult, might make a far more exciting riddle.

In any event, I'm going to guess "Fire" for spite because in the nes version, his hair could be snakes and, for the life of me, I can't imagine that somebody is going to be living very long if he's so immersed in fire that he's hallucinating fire creatures with snakes for hair and, by some freak occurance, poisonous blood.