The Ultimate Book of Spells (2001)

S1E19 Dark Image

Cassy and Gus tease Verne about being a mortie, which frustrates him, prompting him to storm off. He heads to the mortie arcade, where he discovers a magical artifact hidden in his backpack. This artifact transforms Verne into a formidable dark wizard. Soon after, Cassy also undergoes a transformation, becoming a powerful dark sorceress. Now, it falls on Gus to intervene and prevent them from wreaking havoc on the world and turning against each other!