When the Ancient Spirits of Evil-behemoths enslaved by Mumm-Ra and Skeletor-attack Castle Grayskull, the crown jewel of Eternia, it's up to Man-At-Arms, Panthro, Tygra, Teela, Cheetara, Wilykit, Wilykat, Snarf, Orko and a whole host of Masters to protect the Power of Grayskull!