Fragile Souls

Lalin is a teacher by day, assasin by night. Every night she kills to eat, peoples souls, but only the bad ones. But every full moon, the mark on the back of her neck awakens and she loses all control of her body and blacks out. She is controlled and ordered to take souls, but every cresent moon, these souls called Potens give power, so she is ordered to take them and leave them to the underworld. If she does not eat souls for 3 days to stay within immortal stage, her body will be taken to the devil and all chaos will rise.