Severus Snape was the Potions teacher of Hogwarts during the Harry Potter series.
He became the Defense Against Dark Arts teacher 1996, and had the job until 1997.
He also was the headmaster of Hogwarts in 1998. He was killed by the snake of Lord Voldemort, Nagini.

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Unfortunately, his actor died in early 2016.

Rest in Peace, Alan Rickman.