Having been two years since he last fought in a full-on MMA event, former Ultimate Fighter 13 cast member Keon “Black Assassin” Caldwell is eager to eager to return to action at the World Series of Fighting 4 and showoff the complete overhaul he’s given his game. “My trainer and I looked at everything and decided to start over from scratch,” said Caldwell. “We redid everything, so I’ll be a whole different fighter coming out on Aug. 10. “All aspects of my game have changed since the last time people saw me leaving TUF 13.