Filch retires, and a new caretaker takes on the role. (5th year, dimension travel Eragon, one-shot series i guess?)

When Eragon finds an mysterious "blue circle" he decided to check it out. He was not expecting to walk into the world of the Avengers, who were not expecting to see a man falling from a disturbingly similar portal of the Chitauri during the aftermath of the battle. So they "cautiously approached" him. What could go wrong? (M because paranoia and slight cussing)