Metamorphism

Metamorphism is the ability to alter one's physical appearance to that of any other human being.

Raven Darkholme (Mystique)
Mystique can mentally alter the formation of her cells at will. As a result, she can cause herself to look and sound like an exact duplicate of any human, humanoid, or semi-humanoid being of either sex, wearing virtually any kind of clothing. Her control is so exact that she can precisely duplicate another person's retina pattern in her own eyes, finger, palm and skin pore patterns on her own hands and skin, smell to overlap the original being, and vocal cords to match voices to the point of corresponding voice prints.

Mystique was once exposed to dangerous levels of radiation in order to save the life of Toad. The process morphed Mystique's appearance to match her more reptilian physique and boosted her powers so that she could now morph her body into taking certain desired physical traits depending on her situation at the time. Examples of this new ability include night vision, wings on her back, talons on her fingers, sharp fangs, natural body armor, a mermaid-like tail, and she could even compress into a nearly two-dimensional state to glide on air currents.

Since her resurrection, her powers have been enhanced to higher levels than they were before. She can now fool superhumanly acute senses such as Wolverine's sense of smell, something she couldn't do before her death.

Originally, it was clearly stated that Mystique's powers were limited to appearances only; she could not assume the powers of people she morphed into or alter her body to adapt to different situations. Although Mystique's powers were enhanced, she could never duplicate the powers of other superhumans and still cannot. For example, when she turned herself into a duplicate of Nightcrawler, she did not gain the ability to teleport. However, she can use her powers to mimic the powers of others, such as assuming the form of Sabretooth and then using her powers to enhance her senses, strength, speed, agility, and regenerative capability.

While she can make herself look exactly like a person who is physically bigger than herself, she will not weigh as much as the real person does. Although she can maintain the form of a person of her own height, weight, and build indefinitely, the longer she maintains the form of a person physically larger than herself, the greater the strain she feels.
 * Metamorphic Adaptation: After her enhancement, Mystique demonstrated the ability to adapt her body depending on her situation at the time. She was able to camouflage her body according to her surroundings, shift her organs into her lower extremities, and mimic the textures of metals. She also clearly stated that she is always naked and smiply makes her skin look and feel like other materials to fool others.
 * Enhanced Physical Attributes: She is able to enhance her strength, speed, agility, reflexes, and senses.
 * Accelerated Healing: Mystique's nature allows her to repair wounds and regenerate herself from minor to near-death injuries in a short span of time much faster than an ordinary human.
 * Toxin & Disease Resistance: She is also able to develop resistance and immunities to toxins and diseases.
 * Delayed Aging: Her metamorphic powers have delayed the degenerative effects of aging. She has always had this ability, even before her enhancement. Mystique is either close to or over one hundred years old.
 * Psychic Defense: Her nature also provides her with a natural defense against telepathic intrusion.