They are also members of Dumbledore's Army, a group started by Harry, Ron, and Hermione to teach practical instruction in Defence Against the Dark Arts, which Dolores Umbridge has removed from that course's curriculum. Later that year, they are banned from Quidditch and decide to abandon formal education; they do not, however, leave before conjuring a swamp in a corridor. After Umbridge is driven from the school, Flitwick removes it, but leaves a small bit as a tribute to the Weasley twins. In Harry Potter and the Half-Blood Prince, Fred and George continue to run their very successful joke shop, Weasleys' Wizard Wheezes. Though Mrs Weasley initially disapproves of their enterprises, she realises they have a natural gift and passion for their business and has since raised no objections.. George loses one of his ears to Severus Snape's Sectumsempra curse (which is aimed at a Death Eater's wand hand, but misses). As the injury is caused by dark magic, it cannot be repaired. During this novel, the Ministry of Magic (now led by Death Eaters) is watching every member of the Weasley family. It is impossible for Fred and George to return to their shop in Diagon Alley to sell their products, so they begin to run another owl-order business out of their Auntie Muriel's house. During the Battle of Hogwarts, an explosion kills Fred. Towards the end of the novel, George and Lee Jordan defeat the Death Eater Yaxley.