She loved the theater. Ever since the first time she attended a play, she found herself almost lost in admiration for how the performers could seem to become another person, if just for one night. She wondered what it would be like to have that skill. Soon, however, she discovered that is was so much more difficult than the players in that first production she had seen had made it appear—they had been, after all, professionals, experts.
When she met Kyubey, she found herself with the opportunity to fulfill her desire for perfection. So she took it.
Flawless imitation of what the spectators wanted to see, whatever was necessary for the part, made it possible for her to get by without much rehearsal, except that which was needed in order for her fellow actors to practice with her. This was convenient for her, because, being a magical girl, she had to go out and do battle with witches from time to time. As a celebrity of the stage, as opposed to a movie star, she ran less risk of getting recognized for her fame when she was out on a witch hunt. However it still posed a problem. Over time, she began to consider whether she might be able to use her gift outside of the theater, making herself seem like another person, so as to go unnoticed. It took practice, but she succeeded.
As the years went by, she felt increasingly unfulfilled by her 'talent'. She took notice of those around her, working so hard, to gain even a fraction of the proficiency she displayed with ease—granted, it had come at a high price for her, but even so, the discrepancy between herself and the others of her profession brought her unhappiness. Guilt.
It seemed to her that she didn't deserve the treatment people gave her. Her admirers, they were fools; her directors, they were puppets; and her critics, they were nonexistent. This made everything worse. No one could tell her the flaws she exhibited, because there were none, not so far as they were concerned. But to her, she observed with vivid clarity her own faults. And they were driving her mad.
She could always count on everyone around her to give her endless praise, to shower her with compliments—although it wouldn't be long before this deluge of glorifications would eventually drown her. The more she heard herself commended by others, the more she could push away the thought of her shame, which she felt from having unfairly gained her skill and her fame. When those people told her how well she had done, she tricked herself into thinking there was nothing wrong with her actions. Some people had natural talent, and her ability was something like that. She had given up her soul for it and, regardless of whether or not she had known that at the time, that had to count for something.
Deception was so close to her, she deceived even herself.
Naturally, the more time and effort she devoted to satisfying her need for attention, soothing her guilt, the less time that was available to her for defeating witches. And when she did, she was chaotic. Out of practice, unmotivated—at this point, it didn't take long for her soul gem to lead her to become the thing every magical girl thinks they are working towards destroying for good. It transformed into a grief seed, and she was recreated as a witch.
And so, she was consumed by her curse.
This is the Witch of Masquerade.
But her story doesn't end there.
As a witch, she gained new power. Manifesting with a deceitful nature, and being the impeccable actress that she was, the Witch of Masquerade found a way to trick the magical girls who entered her labyrinth into thinking she was one of them. She would sit, with her back towards her victim, her old soul gem beside her, and Kyubey as a companion, seeming in most ways to be just another Mahou Shoujo out on the job. But of course she wasn't. Fooled into approaching her, many a magical girl was lured into her trap this way.
For all her despair, she could never stop acting. Not even when she no longer loved it. It would always be her passion. But passion was different. It became obsession.
She continued, in masquerade. And one might say it was because she lost who she truly was.
