"When he was left alone he wandered over to the lectern and looked at the book. The title, in impressively flickering red letters, was Mallificarum Sumpta Diabolicite Occularis Singularum, the Book of Ultimate Control. He knew about it. There was a copy in the Library somewhere, although wizards never bothered with it. This might seem odd, because if there is one thing a wizard would trade his grandfather for, it is power. But it wasn't all that strange, because any wizard bright enough to survive for five minutes was also bright enough to realise that if there was any power in demonology, then it lay with the demons. Using it for your own purposes would be like trying to beat mice to death with a rattlesnake."