Even though Miguel is pretty much perfect. It seems more logical to wait for you to post your other two characters. Plus it would give me more time to work on mine.
Maybe a sorceress or sorcerer could sleep notice that a Changeling is actually fighting for humanity and trains her. Seeing that if she could a useful ally in fighting the monsters/demons
Maybe start off with Changelings. Then when she starts to change. Her spark turns into a flame. In the end she keeps her human form but also has the ability of a monster.
But then it seems I am borrowing an idea from Bleach with the Vizard's.
I was thinking is it possible for my character to start to become a changeling. But her having having some knowledge of what Is going on. In a desperate urge to keep her humanity feeds of the souls of the monsters/demons. If that is possible.
If not being an apprentice or sorceress will be fine