"Well, what is useful really depends on the person who's making it and what they need, but some potions definitely have more practical uses than others. There's the one that changes a person's appearance into that of someone else. That one requires a bit of the person you want to turn into." Such as had unfortunately happened to Alastor Moody the year before. "There's the Draught of Peace, which relieves anxiety. That was a popular one at exam time. The truth-telling potion, which is colorless and odorless and therefore easy to slip to someone without them knowing." He'd never had reason to use it, but he knows that others have.

"There's one that regenerates lost bones, which is useful more times than you would think." Not only has he heard Harry's story, he spent seven years at a magical school himself. "The most useful, perhaps, at least for a friend of mine, is the one that alleviates the symptoms of lycanthropy."

Oh yes, not only is he a wizard, but he knows a werewolf, too.

"I couldn't make any of them without instructions though. They take several ingredients, added in a specific order."