Once a close friend of Charles Xavier, Raven Darkholme turned against the X-Men and joined Magneto's Brotherhood of Mutants, taking on the identity of Mystique. With the ability to assume the appearance of any person via shapeshifting, she’s determined to protect the mutant race no matter what the cost. However, her actions may end up causing their extinction instead.
Powers
Mystique could manipulate her biological make up and skin cells to take on the appearance of other humans, animals, or even objects (she once disguised herself as a replica of the Statue of Liberty). Damage to her biological tissue is known to heal at a relatively fast rate and she can form a resistance to poisons upon contracting them. Notably, Dr. Hank McCoy mentions to Mystique that given her shapeshifting abilities, she is able to alter and rejuvenate her body's cells and thereby retain a youthful appearance. She can also alter her voice to duplicate exactly that of the person she is impersonating.
Originally, Mystique could not change her overall body mass when taking on the appearance of a person larger or smaller, but thanks to subsequent enhancements she has stated that her body mass is not fixed and can change into someone who is physically bigger than her.
Abilities
Mystique was an expert in espionage and fighting. She is seen as exceedingly knowledgeable, being able to program and work whole computer systems. She is a talented actress and a polyglot, being fluent in about fourteen languages. She has a talent for finding, stealing, and understanding cutting edge weaponry. She was also extremely flexible, able to move her handcuffed arms from behind her to her front, and unlock clamps on her hands with her feet.
Weaknesses
Mystique's powers were limited to physical appearances and voices, meaning that she could not copy any abilities or skills from the person. For example, when she fought Wolverine, she assumed his form and fought him claw to claw, only to have her claws hacked off (they were made of flesh). She also cannot replicate certain traits, such as scent, all the way to the genetic level. This means that there are still flaws to her impersonations, since Wolverine was able to identify her in this manner.
