Originally born as an English nobleman, Lord Monty Fiske spent his life as a world famous explorer and archaeologist. After many years of work, he became obsessed with monkeys. He trained in the art of Tai Sheng Pek Kwar (Monkey Kung Fu) and spent his fortune on genetically modifying himself to be monkey-like, replacing his hands and feet with those of a monkey.
He tricks Kim into helping him steal a quartet of mystical idols, he used them to expose himself to "Mystical Monkey Power" and styled himself, Monkey Fist.
Ron is a main opponent for Monkey Fist, as Ron and Rufus are the only other beings believed to have the Mystical Monkey Power that Monkey Fist holds. Ron considers Monkey Fist his archenemy.
Monkey Fist also has an army of monkey ninjas under his control.
Monkey Fist is the only villain on the show who was "killed" off. He is encased in stone after he tries to kidnap Ron's little sister and it is shown in the series finale that he is still in stone.