Powerful psychic CHARLES XAVIER brought together young mutants, like the telekentic MARVEL GIRL, to teach them to control their powers, protect others, and show the world that they were not a threat. But some mutants had a different goal. The power-hungry Brotherhood, including the high-hopping TOAD, fleet-footed QUICKSILVER and illusion-casting MASTERMIND, would make it very hard for humanity to accept Xavier's "X-Men" as a force for good.