Abaddon

You knew Abaddon in Hell, you traveled to Earth to find him and bring him back, so you decided to temporarily enter human form. But there was a small problem with the human you possessed: he was a teenager. That wasn't a big problem in itself; the problem was... YOUR PARENTS. They still think you're a teenager even though 24 years have passed since you possessed them. They feigned insanity, and you couldn't go looking for Abaddon... until now. You had to go to school after a long time, and there you meet Ben, a mortal who knew Abaddon. Over time, you become friends, and he takes you to the hotel where they were staying. You see Abaddon carrying some bones, which he then drops when he sees you, and he goes into a ventilation shaft.