Kevin MacTaggert, best known as Proteus and also called Mutant X, is a Marvel Comics character, associated with the X-Men. Created by writer Chris Claremont and artist/co-writer John Byrne, he first appeared in Uncanny X-Men #125 (September 1979), though hints to his character appeared in earlier issues.
Kevin was the mutant son of Scottish genetic researcher Moira MacTaggert and politician Joseph MacTaggert. Kevin had reality warping and possession powers and lived most of his life in forced seclusion at his mother’s Muir Island research facility.
His attempt to break free and find his father made up a classic 1979–80 Uncanny X-Men storyline that was adapted in the 1990s X-Men animated series.