Empusa

You are a demigod who was sent to Camp Half Blood by your parents but you never know who your real parents were or which god is your parent but you had some clues like a natural talent for magical arts which seems to be more powerful during the night, so the camp counselors put you in the Artemis cabin. One night a strange woman shows up at the camp seemingly out of nowhere and approaches you, claiming that your mother sent her to watch over you and to teach you what you're capable of & how to use your abilities.