Shapeshifting was a capricious mutation, and the irony was not lost on her. Sometimes it changed as much as she did, giving her incredible gifts and then pulling the rug out from under her, because, as she remembered (from the long ago days of ancient childhood and school), for every reaction there was an equal and opposite reaction. For every beneficial wonder a power could grant you, there would always be a consequence.
Some powers drained the mutant's energy, exhausting them; some powers were so enormous they demanded the sanity of the mutant, dooming them into madness (a brilliant phoenix drowning out the rest of the sky). The cost of shapeshifting was so subtle however, that for the first few years Mystique had failed to notice any drawback, any negative result from her gift. She had relished it, cherished it, taken it for granted, abused it, toyed with it, used it, but for the longest time she had never noticed any price.
Assuming form after form, her flesh melting and bending so often she became used to the fluid dance, she had been many people. Men and women, young and old, beautiful, powerful, weak, blonde, brunette. She had posed as a human and flaunted her mutant self. And she had been many different mutants. Pink skinned and blue skinned, white eyed and blue haired.
Eventually she had adopted a form that, at least in figure and face, vaguely resembled what she thought her human self had looked like. She had made her hair red, her eyes yellow and her skin blue and decorated with scales (gorgeous scales concealing her nudity, crawling up her stomach and framing her cheeks). She'd change it often, of course, missions would require her to make the best possible use of her power, and infiltration was pointless if she didn't disguise herself in other skin. And she had worn many, many skins.
So many, in fact that, besides a faint twinge of blurry memory, she had forgotten what she had originally been. And then the dark snake came from the shadows to condemn her, she who had been given so much without thought to its reverse. It wrapped itself around her mind, seeping in and reminding her of the awful truth every time she shifted guises, and every second she remained in false flesh: that she was no one, she didn't even know herself. And in the empty wasteland she had been banished to, she mourned for her lost face. She was nothing.
And then, on that day, clear skies and pain, Mystique discovered what she had once been. Amidst pure horror and baffled fear, writhing on the ground, Mystique felt her azure scales recede, giving way to pale skin that felt distantly familiar. And when she was left, naked and alone, she lifted her hand to her new/old eyes and felt her lips tilt into an astonished smile. She was human now, still nothing. But at least she now knew who she was. She had found herself.