Sakuya Izayoi

The first Defense Against the Dark Arts teacher of Harry Potter, Professor Quirrell maintained a severe sense of mystery throughout the first installment in the HP series. Harry sympathized with his professor, as Quirrell often seemed nice, though was terribly afraid of everything remotely fearsome and stuttered horribly. However, Harry's impression of Quirrell turned out to be dead wrong when the professor revealed himself to be the villain of the story, and a pawn in Lord Voldemort's master plan. He traps Harry in a chamber with the Mirror of Erised by clicking his fingers to make fire appear there. Then makes Harry use the Mirror of Erised to make the Philosopher's Stone appear in his pocket. He then removes his turban to reveal Voldermort's face on the back of his head. Voldermort demands for the stone, and offers to bring Harry's parents back to life in return. When Harry shouts "You liar!", Voldermort orders Quirrell to kill Harry, and Quirrell starts strangling Harry. But the power of Harry's mother's love for him inside his body burns Quirell to a pile of dust, and Voldermort flees his body.

Archive footage of Quirrell (from "Philosopher's Stone") was later shown in "Deathly Hallows Part 2" (which was released ten years after the first installment), when Harry was watching flashbacks of his life through Dumbledore's Pensieve using Snape's tear.