Deci

As a human she was Caldera Philia. Her parents died during a supernatural fishing accident and because of this most of her life she was somewhat raised by her 10 years older brother Mascon. Once Caldera entered into school it quickly became apparent that she would need to be tutored more closely, partly because she was a child prodigy and partly because she'd often pick physical fights with her peers. By her teens she had become incredibly competitive in school as well as developed severe insomnia. It's no wonder that she only had about two friends.

Her school prepared her for the life of academia and lab study, most of which was studying supernatural cells in hopes of turning infected humans back to being humans. Most biological therapy at the time for curing the supernatural worked by killing the supernatural parts of the body. If there was enough human left to function than the patient was cured. Caldera sought out to reverse engineer humanity, then she could create a disease that would (hopefully) turn the supernatural human again. She studied this process by making plant based hommunculi.

In studying humans, she liked them less. Humans were emotionally flawed, and sick and weak. The moment a demon gave her the chance to leave her humanity behind she took it.

Caldera became Deci. Her insomnia was cured because she no longer slept, her bruised fingers ceased hurting because she had no blood, she no longer tripped over herself because she could just fly. This was the best thing to ever happen to her. If only everyone else could become a ghost too..

She left her old lab behind to pursue a closer study of the supernatural, only bringing with her one of of her test subject homunculi as a butler.
She is presently hoping to one day turn large amounts of people to be like her too.