Severus Snape
Wizard, Professor
Snape. Snake. Get it? He's in Slytherin House. Because he's a snake. Hssssss-sssssssssssss.
Professor Severus Snape was an English wizard serving as Potions Master, Defence Against the Dark Arts professor, and Headmaster of the Hogwarts School of Witchcraft and Wizardry as well as a member of the Order of the Phoenix and a Death Eater. Anything more said about Severus would venture into spoiler territory, so our lips are sealed.