He-Man and the Masters of the Universe: The Complete Original Series DVD Box Set

Eternia is a planet of magic, myth and fantasy. Prince Adam is the young son of Eternia's rulers, King Randor and Queen Marlena. Whenever Prince Adam holds the Sword of Power aloft and proclaims "By the Power of Grayskull!" he is endowed with "fabulous secret powers" and transformed into He-Man, the most powerful man in the universe.

Together with his close allies, Battle Cat (who undergoes a similar transformation from being Adam's cowardly pet tiger Cringer), The Sorceress, Teela, Man-At-Arms and Orko, He-Man uses his powers to defend Eternia from the evil forces of Skeletor. Skeletor's main goal is to conquer the mysterious fortress of Castle Grayskull, from which He-Man draws his powers. If successful, Skeletor would have enough power to rule all of Eternia and possibly the entire universe.