He-Man and the Masters of the Universe (1983)

S1E30 The Return of Orko's Uncle

A nefarious character named Azrog is captured on Trolla by Uncle Montork, only to escape to Eternia and ally himself with the witch Spydra. Montork pursues him, but finds himself locked away in Spydra's fortress. Meanwhile, He-Man, Battle Cat, Teela, and Orko embark on a mission to save Montork. However, during the rescue, Azrog casts a spell on Orko, corrupting him and turning him against his allies.