Jungle demon use to be a little boy who, for some reason, was left all alone in Fantomah`s jungle (maybe his parents died in an accident). He was taken by a giant female snake, who decide no to eat the boy, Instead, she raised him (the boy called her Powerhouse).
He grew up to be a man. One day, he ate berries that should not be eaten. He changed to an evil mastermind, who wanted to do evil things. And alot of inconvenience he did give to the jungle and its residents.
His reign of terror was stopped by Fantomah, who changed him back to his former self. Then, she doomed (or "doomed") both the former Jungle demon and Powerhouse to live in isolation for rest of their lifes, on a vast jungle area. For some reason.