Listen to the sound clip No one. from Severus Snape Clips - Harry Potter: No one. No one. This sound is from Severus Snape Clips - Harry Potter Severus Snape portrayed by Alan Rickman was Potions Master, Defense Against the Dark Arts professor, and Headmaster of Hogwarts School of Witchcraft and Wizardry. He played an important role in the war against Voldemort. Go to the full soundboardwith more sound clips Search