Many years ago, a team of super-heroes who preceded the Champions designed a built a robotic servant to serve as guard and a butler for their headquarters. But something went wrong with the robot's programming and it turned on it's creators.
Mechanon considers the Champions the rightful successors to that original group of super-heroes and has fought them on four different occasions. Time and again, the creature known as Mechanon has been rebuilt. Each time more powerful than before.
Thus far, Mechanon has been defeated each time. But as he himself has observed, to accomplish his aims, he will only have to win once.