Boggart

Boggart of Ron's fear

Background

A Boggart is a shapeshifter which takes the shape of whatever a person fears the most.

During the events of Harry Potter and the Prisoner of Azkaban (2004)

Professor Lupin shows the class a wardrobe with a Boggart inside of it. He teaches them, a way to repel a Boggart is to cast the spell Riddikulus along with laughter. The students, including Girl 2 then practice chanting the spell. Neville Longbottom is chosen to go first, and then the class continues with Ron Weasley going next, followed by Parvati Patil and then Harry Potter. When it is Harry's turn, the Boggart turns into a Dementor and Lupin is forced to return the Boggart to the wardrobe.