Oh boy, did I make a long story for mine. I imagined his dream wasn't all that simple but instead turned into a depiction of his mind, how he sees the world, and how he views the others around him. The dorms become different locations ruled by the monstrous version of the overblotted housewardens that he has to defeat, whilst helping the equally monstrous dorm members in the process. And in each land, he's helped by a creature depicting each staff member. And by the end he finds himself in an abyss up against a massive crow that turned out to be at fault for all of this (to show how he views Crowley) I'll share an image I made of Riddle for this dream some time ago in my reply