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Professor Horace Eugene Flaccus Slughorn (b. 28 April, between 1882 and 1913) was a British pure-blood or half-blood wizard. He attended Hogwarts School of Witchcraft and Wizardry as a member of Slytherin before returning in 1931 as Potions Master. He also served as Head of Slytherin House, before retiring in 1981 due to a fear that Albus Dumbledore would discover that he had told Tom Riddle about Horcruxes. Following the return of Voldemort and the Death Eaters beginning to seek Slughorn out, the retired professor lived a life on the run, unsure if Voldemort intended to recruit him or kill him to keep his Horcruxes a secret. In 1996, Dumbledore convinced Slughorn to return to Hogwarts by tempting him out of retirement with the prospect of "collecting" Harry Potter as he had so many other students, with his true goal being to learn what Slughorn had told Riddle. Slughorn eventually divulged his true memory. He continued to teach during the 1997–1998 school year under Voldemort's regime, and was surprised to learn that Voldemort meant to recruit him only to teach the young wizards that Voldemort would deem suitable to attend Hogwarts. During the Battle of Hogwarts, Slughorn sided with the defenders of Hogwarts, gathering reinforcements from Hogsmeade, and engaged his former pupil in a duel alongside Minerva McGonagall and Kingsley Shacklebolt. He survived the battle and had retired a second time by 2016, having a portrait hung in the Slytherin Dungeon.
He attended Hogwarts School of Witchcraft and Wizardry from the age of eleven and was immediately Sorted into Slytherin House. Horace excelled at school and became friends with Muggle-borns even though his parents didn't agree with it.However, Horace did already have a need to play favourites with anyone he considered talented enough and loved to make out that he knew famous people, such as the Minister for Magic who he would refer to by his first name to try and convince others he was close to him.
Slughorn was not able to hide forever, though, as he discovered one evening in the summer of 1996 when Albus Dumbledore and Harry Potter came to call in the Muggle village Budleigh Babberton. In an attempt to escape Dumbledore, Slughorn faked a struggle, wrecking the house, splashing his last bottle of expensive dragon blood on the walls and disguising himself as an armchair. He hoped Albus would be fooled into thinking the Death Eaters had kidnapped or killed him; in his haste, however, he forgot to cast the Dark Mark over the building. Dumbledore saw through this guise and forced Horace to reveal himself.
After the battle, he sat at the Great Hall by Pomona Sprout and Filius Flitwick, telling of how he had lost his wand during the fighting, but eventually found it in the folds of his gowns and "dispatched" a few Death Eaters.