Full Summary:

What would you do if your mother was half demon, half witch and your father was half witch, half white lighter? What would you do if the Source had your parents killed because they were a thereat to the demonic world? You'd go after every demon that had a hand in killing them of course. You're about to meet a girl from the Charmed One's world who goes to Hogwarts. How do her peers react when the Charmed One's appear and ask for her help? Can anyone guess? Well you're about to find out. This girl has a lot on her plate. Student by day, demon killer by night! Hell yeah!

Prologue will be italics.
Prologue:

My father was assigned to watch my mother. The white lighters never knew that she was half a demon. And my mother never knew that my father was half of a witch. Both my parents had gone to Hogwarts. But neither had gone at the same time. My mother had gone 60 years after my father. My father had been killed in a car accident but his body was never buried with a name. Nobody knew his name because he hadn't registered in the country yet.

My mother was assigned by the source himself to live in the mortal world as a human. He knew she was half witch. In fact, he had recruited her right after she had gotten out of Hogwarts. The wizarding world lost track of both my parents after they left Hogwarts. They were never to see them again until I stepped into Hogwarts 16 years later.

Unfortunately for me, when I was four years old, the source had my parents killed off because they were a threat to the wizarding world. I wasn't in the room at the time, but I did hear my mother and father scream as they were being killed. When I reached the age of ten, I took it upon myself to go down to the underworld and learn which demons had killed my parents. I've been hunting them ever since.

I've been in Hogwarts for nearly three years and nobody knows what I've been doing on the weekends. Nobody needs to know. It's my business and nobody else's. I never expected the Charmed One's to show up with their white lighter or one of the demon's that had killed my parents, but they did.

Cole was his human form. But his demonic form was Belthazar. I remember his face distinctly as he was one of the only demons to come into my room after killing my parents. He had seen me, but told them that nobody was in the room. He let me live, but I still have to kill him.