The Diadem of Rowena Ravenclaw

"Luna did not think it strange at all for a disembodied voice to be talking from nowhere. "You're welcome," she murmured as she hopped off the desk and beamed up at the bust before turning and skipping out of the room, the door sliding smoothly shut behind her." Luna Lovegood has had past experience with the diadem of Rowena Ravenclaw, but she felt that it wasn't necessary to tell.