Yen Sid

Yen Sid is a teacher of Weird Science at Dragon Hall on the Isle of the Lost. He went there on King Beast's request to teach the villain kids. He is the founder of the Anti-Heroes Club. Despite being on the Isle, he had direct communication with Auradon and frequently communicates with then King Beast (and later King Ben) about how things were going in terms of education. He got to return to Auradon after the VK Program is set up. He now teaches Magic 101 in Auradon Prep to help students with magical properties

Before Auradon
Yen Sid was a powerful sorcerer who had an apprentice, Mickey Mouse. When Yen Sid left, his apprentice later took his hat to learn magic from himself, after Mickey brings a broom to life and to do his job. It ended up filling the whole room with water. Yen Sid returns an stops the chaos and realizes that it was his apprentice's fault and sends him back to work.