Imitation: The changeling was a human metamorph. Through psionic means he could alter his entire physical appearance with Amazing ability. He could also change his voice and would appear as if an exact duplicate of any individual. He could not duplicate powers.
Psionic Powers: During his stint as Professor X, he was granted the powers of telepathy and mind blast at Excellent rank.
Virtually nothing is known about the mutant known as Changeling, although he had used his mutant powers to successfully engage in many criminal activities. Because of these crimes, he was contacted by the so-called Mutant Master to join the subversive mutant organization Factor Three. The Changeling in turn recruited other villainous mutants for the team, namely, the Blob, Mastermind, and Banshee, who had to be brainwashed to serve them and was freed by the mutant heroes, the X-men.
Later, Factor Three kidnapped the X-men leader, Professor X in order to capture the mutant heroes. Factor Three put the X-men on trial for treachery to the cause of mutant domination of Earth. The X-men broke free, however, and stopped Factor Three’s current attempt at world domination. At the same time, the Changeling, who had grown suspicious of the Mutant Master, appeared in the guise of Professor X to confront him. Ultimately, the Mutant Master was revealed to be an alien exploiting the mutants of Factor Three for his own agenda. The real Professor X then led the X-men and Factor Three to defeat the Mutant Master, and the two teams parted ways.
A short time thereafter, the Changeling learned he had a terminal illness and would not live more than six months. He contacted Professor X, wanting to do something to make up for his past crimes. Professor X had Changeling impersonate him so that he could focus all his attention and power on another pending alien invasion. Only the X-men known as Marvel Girl (now, Phoenix) knew of Changeling’s new role. As Professor X, the Changeling led the X-men for a considerable time.
Then, in conflict with the subterranean villain Grotesk, the Changeling was instrumental in stopping Grotesk’s plans to destroy the surface world. However, Changeling was fatally wounded by being too close to Grotesk’s doomsday device as it exploded. He died a few months later, knowing he had redeemed himself through his sacrifice. (It would not be until months later, when Professor X reappeared as the alien invasion was moving closer, that the X-men learned that the man who died was Changeling.)
Changeling’s body was reanimated by the villainous voodoo priest Black Talon, who wanted to use mutant zombies in crime sprees. Changeling subversively allowed the hero She-Hulk to defeat the villain. He was laid to rest again, not wanting to repeat his past mistakes as a villain after he had been allowed to be a hero.