The Dueling Club Incident

Gilderoy Lockhart and Severus Snape start a Dueling Club for students. During a demonstration, Lockhart is easily disarmed by Snape. When students pair up to practice, Snape pairs Harry with Draco Malfoy. Malfoy conjures a snake with the spell Serpensortia, which threatens a Hufflepuff student, Justin Finch-Fletchley. Harry, without thinking, speaks to the snake in Parseltongue, commanding it to leave Justin alone. The snake obeys, but the crowd is horrified, as Parseltongue is a rare and dark ability associated with Salazar Slytherin. The incident fuels rumors that Harry is the Heir of Slytherin, and Justin, along with many other students, becomes terrified of him. Harry is now widely suspected of being behind the attacks.