The planet Eternia is in the aftermath of Skeletor's war on Castle Greyskull, which he has won after seizing Greyskull and the surrounding city using the Cosmic Key developed by the Thenorian locksmith Gwildor. The Sorceress is now Skeletor's prisoner and he begins to drain her lifeforce as he waits for the Eternia's moon to align with the Great Eye of the Universe that will bestow god-like powers upon him. Once on Earth, He-Man and company team up with two teenagers as they attempt to find the key and return home. However, the evil Skeletor and his vile minions are soon hot on their trail.