Azalie Cait-Sith

Alternate Spelling: Azalea

She is Orphen's foster sister, best friend, and the Bloody August. They were in the same orphanage and came to the Tower of Fangs together, believed to be magical-prodigies. She tutored him a lot, and gave him special attention. She was a great sorcerer—maybe one of the greatest. However, she had two sides to her: the kind, loving Azalie and the, as Orphen says, "scary" Azalie. After having her love declaration to someone else rejected, she seemed to be almost obsessed with her studies; she wanted more power, and one of her experiments turned her into Bloody August—the name given to the dragon that first appeared in August.

(Source: Wikipedia)

The information above regards the anime by J.C Staff and is different from the novels/remake.