On the planet Eternia, Skeletor and his dark army overthrow the Sorceress of Castle Grayskull expecting to acquire her power. He-Man, his old friend Duncan "Man-at-Arms" and his daughter Teela are attacked by Skeletor's soldiers and they defeat them. They also rescue their prisoner, the inventor and locksmith Gwildor. He explains that he was lured by Evil-Lyn that used his invention the Cosmic Key to open the gates and seize the Castle Grayskull. He-Man and his friends retrieve the prototype of...