Dumbledore's youngest sister. Her existence is shrouded in mystery and rumor: many believe that she wasn't actually a witch and, to cover this up, her mother Kendra kept Ariana locked up like a prisoner until her own death, while Ariana died not long after at Dumbledore's hands. The truth, however, is even more tragic. Ariana was a witch but, when two Muggle boys found her and she wasn't able to perform magic for them, they abused her, possibly sexually, which permanently damaged her mind and caused her to repress her magical abilities. Kendra did keep her locked up, but only to keep Ariana from being forcefully placed in St. Mungo's, as Ariana's moods were unpredictable and when she became angry, her repressed magic made her dangerous. Ariana accidentally killed Kendra in one of her rages. Aberforth explains to Harry that he and Ariana were extremely close, while Dumbledore saw her as a burden. She died during a three-way duel between Dumbledore, Aberforth, and Grindelwald, and it's unknown whose spell actually killed her. Her portrait hangs in Aberforth's sitting room and she's able to bring people through a tunnel that leads to the Room of Requirement.