After experiencing traumatic nightmares of a time now past, the Sorceress summons Prince Adam and Cringer to Castle Grayskull to give Adam a precious, jeweled sword and send the pair to the planet Etheria to investigate its secrets. Unsure of what they are expected to find, the Prince and his companion befriend the Great Rebellion, a small group of citizens fighting a huge intergalactic army, known as the Evil Horde, ruled by the vicious tyrant Hordak. During a titanic battle, Adam transforms into He-Man to help the rebels, but is soon captured by the Horde's Force Captain, Adora, and placed under Horde surveillance. Adora is disturbed from her sleep by a strange voice, which leads her to the site of the imprisoned He-Man, where she is greeted by the Sorceress of Grayskull, speaking to her through the jewel in the mysterious sword The Sorceress reveals the terrible truth behind Adora's past - she is a Princess. not only that, she is He-Man's twin sister - kidnapped by the Horde when she was just an infant! Adora seizes the magic sword, holds it high above her head and summons the power of Grayskull! With this, she is transformed into the magnificent She-Ra, Princess of Power, and frees her brother. Reunited at last, the Prince and Princess vow to return home to bring the Eternian Royal Family together again and attempt to free the Kingdom of Bright Moon from Hordak's reign of terror!