The Battle of the Astronomy Tower, also known as the Battle of the Lightning-Struck Tower, was a battle of the Second Wizarding War that took place in the topmost tower of Hogwarts School of Witchcraft and Wizardry in June of 1997. It occurred per the design of Lord Voldemort, who had ordered sixteen-year-old Death Eater Draco Malfoy to find a way to sneak other Death Eaters into the school and to assassinate Albus Dumbledore, the leader of the Order of the Phoenix. Malfoy succeeded in the former, but was unable to do the latter. As the Order and the Death Eaters battled, Severus Snape killed Dumbledore, which was actually what the headmaster asked him to do.
Bill Weasley, a member of the Order of the Phoenix, was badly bitten about the face by werewolf Fenrir Greyback when he was not transformed which left him with severe scarring. None of Dumbledore's Army was badly hurt despite many killing curses because Harry had given them some of his Felix Felicis (Liquid Luck).