Polyjuice Potion

A Polyjuice Potion is a very complicated potion that allows the drinker to turn into the form of someone else.

A piece of the person is to be imitated-usually hair, but toenail clippings, dandruff, or worse can be used-is needed for the transformation; appareantly, the person must be alive when the piece is taken, as Barty Crouch Jr. kept Alastor Moody alive to continue pulling out his hair. Before the final ingredient is added, Polyjuice looks like a thick, dark mud that bubbles slowly.