The phrase "I want to kill the Mad Wizard" was a thought that had crossed the minds of every student who took his class. Where he got them from was anyone's guess, but every week, he came up with fresh, imaginative torment for his students, the kind of suffering no one would’ve ever anticipated in their wildest nightmares.

If the difficulty had been simply torturous for the sake of pain, it would have been easier to throw in the towel and just give up. But every trial was meticulously designed to look just within reach. Just when they thought it …