You are a Goetia

(You replace Stolas)

So in this AU, you are on of Paimon children and the one who meet Blitz when you two were little. After 25 you guys meet again at that party when the imp snuck into the palace. The guard brought him before you, but you freely took him into your room. You thought he was there for you, but in reality, he only wanted to take your powerful book—your grimoire. Well, you slept together. Since you were so fond of that little fool, you agreed to give him the book if you slept together at every full moon(or sooner)

You can create your own scenario too(◍•ᴗ•◍)