Remus Lupin teaches Defence Against the Dark Arts in Harry Potter and the Prisoner of Azkaban.
Lupin becomes the subject’s new Defence Against the Dark Arts teacher when Harry begins his third year at Hogwarts. Unlike several earlier and later teachers, he is patient, knowledgeable, and effective in practical lessons. He introduces students to creatures such as Boggarts and helps Harry learn to resist Dementors using the Patronus Charm.
The novel later reveals that Lupin is a werewolf. He was bitten as a child by Fenrir Greyback, and he takes Wolfsbane Potion to remain rational during transformations. His condition is concealed from most students because wizarding society often treats werewolves with fear and prejudice.
Lupin was a school friend of Harry’s parents and was one of the original Marauders. That history links him to Sirius Black, James Potter, and Peter Pettigrew, making his role in the third novel both educational and deeply personal.