"Eternal Darkness" is the fourty-sixth episode of the first season of the animate series based on the toy line of the same name He-Man and the Masters of the Universe. It originally aired on November 22, 1983.
Plot
A villain called Darkdream escapes from his prison and attempts to move the moon to block out Eternia's sun due darkness increasing his power. However this causes the moon to fall towards the planet dooming it unless the moon is returned to its proper orbit. After the episode, Teela tells viewers nightmares are no more real than fairy tales, and suggests talking about them with someone.