He stared at the raven Patronus in complete surprise. He was probably also under the assumption that a Dark Arts user could not summon a Patronus. "If you want to talk about  evil . That book right here," I said as I pointed at a singular book that felt wrong to me. "That one is bad. I imagine that book has something about death magic. Like the Killing curse." Sure, I was using my own feelings about the book, but if my assumption was right. That book showed how to use the Killing curse and should be marked as.. very dark.