And the second addition to my collection of villainesses-turned-slaves, we have Princess Azula, of Avatar the Last Airbender. Here, I'll admit I used a bit of trickery.

Following the events of The Search, Azula was looking for a way of becoming stronger and more powerful so she could overthrow her brother. So, I approached her in disguise and offered her the Power of the Phoenix, if she would agree to do a single favor for me afterwards.

I knew, of course, she was planning to betray me. But she should've been more careful about my offer. So I granted her the power she desired by joining a phoenix spirit to her. Mind you, I neglected that some side-effects of spirit joining include losing part of one's mind due to fusing with another mind. So she was left quite vulnerable to a Charm Person spell, and soon became my thrall.