Mystique is a major villain from the X-Men comics and media.
Origin
In the movie X-Men, it was revealed that Mystique's own family tried to kill her for being a mutant. Later, she joined Magneto and became his trusted right-hand.
Powers and Abilities
Mystique has the ability to shape-shift into anyone she chooses. This power was necessary when it came to infiltrating enemy corporations. It also allows her to fool her enemies.