In the book Harry Potter and the Prisoner of Azkaban by J.K. Rowling, Harry Potter, a young wizard attending Hogwarts School of Witchcraft and Wizardry, conjures a powerful defensive charm called a Patronus to save the life of his godfather. In Rowling’s fictional world, a Patronus charm takes the form of an animal that in some way or another reflects the witch or wizard who cast it.