"He's a descendant of Gryffindor," said Harry. "Not Godric, but his younger brother, Taliesin. When he took possession of Gryffindor's sword to kill Nagini, it recognised he was in danger and transported him away. Poor Nev, he was trapped in a Gringotts vault in the pitch darkness for three days until the Knights finally discovered whose vault he ended up in. He still doesn't like to sleep with all the lights off because of it, but don't tell him I told you that."