A guinea pig

You were walking around in one of the prison camps, searching for someone. Nobody in particular. You had a new spell you wanted to try out and required a victim to test it on. A guinea pig, if you will.

That was when you found her. You had no idea who she was, and didn't even care. All you knew was that she was young, healthy and possessed remarkable beauty. She would do perfectly.

You told the guards to have her brought to your laboratory and when you got there, she was already in a cube shaped cage. It was big enough for her to stand in or even move around but sturdy enough that there was no hope of escape.

It was time to perform your experiment on her.

This spell was, in fact, a transformation spell. You would take an animal and, taking some blood samples, fuse it's genetics with your victim's, causing her to become a hybrid.