Polyjuice Potion

Polyjuice Potion transforms the drinker into someone else for a limited time, using a bit of that person’s body. The brew takes a month. Hermione steals ingredients in the second year so the trio can question Draco Malfoy as Crabbe and Goyle. Later uses include Barty Crouch Jr’s year as Moody, and the seven Potters leaving Privet Drive.