The Power of Grayskull is the 35th episode of the 2002 He-Man and the Masters of the Universe series.
Prince Adam awakens from a dream involving Hordak, the Snake Men, and a warrior very similar in appearance to He-Man. He goes to Castle Grayskull to learn more about his strange dream from the Sorceress.
At Snake Mountain, Hordak commands Skeletor to go to his former sanctuary to free him from Despondos, the dimension were he is imprisoned. This is the price he must pay for having his life saved by Hordak so many years ago.
The Sorceress tells Adam that the warrior in his dream was King Grayskull, the former ruler of Eternia and lord of Castle Grayskull. He was a great and noble warrior, married to Veena, the original Sorceress. Grayskull had recently lost his sword in battle against the Snake Men and sought the power to defeat Hordak. Hordak had banished the Snake Men and planned to conquer Eternia at any cost. Veena directed King Grayskull to go to the Oracle for advice. Once he found the strange creature, the Oracle sent him on a quest that that tested and proved his courage, wisdom, kindness and strength.
Once Grayskull finally reached the top of Mount Imperium, he finds the Oracle had already arrived. Once he overcomes his shock he presented him with his lost sword and told that Grayskull's true power was within him and always had been. The Oracle went on to add that Grayskull would not survive the coming battle fight with Hordak. Grayskull faced his fate without fear and returned to defend Eternia.
Hordak and his forces advanced upon Castle Grayskull. King Grayskull's giant cat trounced the soldiers and Grayskull easily defeated Hordak's generals. The two enemies faced each other, but Hordak knocked him back unleashing his full power. He commanded his wizards to open a portal to Despondos so that he could send King Grayskull there. Grayskull drew upon the power within, commanding that he had the power, protecting Castle Grayskull from entering Despondos. Using the Sword of Power Grayskull reversed the spell, and the portal sucked in all of Hordak's forces. Hordak physical being destroyed, he became a spectral form and flew straight through King Grayskull on the way to Despondos, threatening to return.
King Grayskull had beaten Hordak, but at a price. Hordak had struck a fatal blow, so King Grayskull left his power to fill his followers, who became the Council of the Elders. He then left his sword to Veena so that one day, when it was needed, a great warrior could wield it in battle against evil. The Sorceress swore to guard it until the day that she must give up her position to another. King Grayskull then died in the company of those who loved him, his spirit passing into the Sword of Power.
Adam, upon learning all of this, changes into He-Man and goes to stop Skeletor from freeing Hordak. Instead of freeing Hordak, Skeletor destroys his former sanctuary, stopping him from returning and breaking his bond with him. He-Man, as well as Evil-Lyn, looking on from a distance, wonders why.