Dumbledore's Army
At Hogwarts, Dolores Umbridge, a senior Ministry employee, becomes the new Defence Against the Dark Arts teacher. She refuses to believe in Voldemort's return, and clashes with Harry, punishing him by having him magically carve "I must not tell lies" into the back of his hand. She also refuses to teach her students how to perform defensive magic, prompting Harry, Ron, and Hermione to form their own Defence group with other students. Umbridge, empowered by the Ministry to interfere in Hogwarts as the new High Inquisitor, bans unapproved clubs, forcing the group, now called Dumbledore's Army, to meet in secret in the Room of Requirement to practice under Harry's instruction.