The Battle of the Department of Mysteries was the beginning of the Second Wizarding War, which eventually resulted in Hogwarts' destruction. This battle took place in the Department of Mysteries, which is where its name came from. It resulted in the death of Sirius Black, which altered Harry Potter's life.
Harry, Ronald Weasley, Hermione Granger, Ginny Weasley, Neville Longbottom, and Luna Lovegood flew to the Ministry on Thestrals, where they went to Level 9 and down the hallway to the Department of Mysteries. They found 12 identical black, handle-less doors. When each door behind them closed, the walls spun, and the doors returned to different places. They went through one, which turned out to be the Brain Room and went back to the Entrance Room and try another, which turned out to be the Death Chamber. The next door they tried wouldn't open by any means of enchantment, but the next room, the Time Chamber, contained the glittering lights from Harry's dreams. Once in this room, they took another door to the Hall of Prophecy but didn't find Sirius there. In the row where Sirius was supposed to be, Harry spotted an orb with his and the Dark Lord’s names on it. This alarmed twelve Death Eaters — Rodolphus Lestrange, Rabastan Lestrange, Antonin Dolohov, Avery, Walden Macnair, Crabbe, Nott, Augustus Rookwood, Jugson, Mulciber, Bellatrix Lestrange, and Lucius Malfoy.
The group began to duel the Death Eaters, and proved themselves good at wandwork. They were struggling, though, and several members of the Order Apparated: Sirius Black, Remus Lupin, Nymphadora Tonks, Kingsley Shacklebolt, and Alastor Moody. Everybody began dueling. Harry and Sirius got in a duel with Lucius Malfoy and Antonin Dolohov. Harry disarmed Antonin, and Sirius disarmed Lucius. However, Sirius was hit by a Killing Curse from Bellatrix Lestrange and was knocked into the Veil.
- Harry Potter and the Order of the Phoenix (book) (First appearance)
- Harry Potter and the Order of the Phoenix (film)
- Harry Potter and the Order of the Phoenix (video game)