"There was a bad man, a Dark wizard, who was very powerful around the time we finished school," Sirius says, "and he... he had some dangerous views, that certain people shouldn’t have magic, or that people who don’t have magic are somehow lesser than people who have magic. When we left school—that is, your parents and the two of us, as well as some other classmates of ours—we signed up to fight this man and his followers."