The Changeling is said to have been the first X-man to die in action, although some also say that that title belongs to Thunderbird. His true identity is unknown, and it is not even to certain of what his true face looks like. His mutant ability is like that of Mimic: he can change his appearance, costume, and voice to imitate any other being. Factor Threewas bent of world conquest when he was in it (A real shocker, that). But he rejoined the X-Mento defeat the Mutant Master. he turned out to be an alien and not a mutant at all. Changeling discovered he was dying. He came to Xavier and begged him for a way to atone for what he had done. Xavier asked him to masquerade as the Professor so he could secretly plan against an attack against the Z'nox. Changeling, as the Professor, died in action against the for Grotesk and was buried as Xavier. For a long time it was believed that Professor X was dead, but Changeling was finally given the recognition he deserved.