Castle Grayskull is a large playset and is a fortress located on the planet Eternia. Being the target of numerous attacks by Skeletor, Hordak and the Snake Men, Castle Grayskull is the place where the secrets lye which, if discovered, will allow them to rule over Eternia.

Castle Grayskull as it appears in the Masters of the Universe Mini Comic

Castle Grayskull was Eternia’s ancient and legendary fortress of mystery and power. Its origins were obscured by time, and no one remembered who built it. All that was known was that it had been erected long ago, before the Great Wars. There was immense power hidden within Grayskull’s ominous, skull-shaped exterior and impenetrable walls. In this place of wonders, whoever controlled Castle Grayskull controlled the universe. While arcane magic permeated its very essence, it was also outfitted with advanced weaponry and computer technology. Among these was a large two-barreled laser cannon mounted atop one of its towers. Castle Grayskull was filled with weapons and strange, shadowy rooms. Enemies could be sent falling into the castle’s dank dungeon on its lower level through a trapdoor in the throne room. The castle was guarded by an ethereal spirit who communicated with the great heroes of Eternia. The spirit knew, but did not disclose, that He-Man himself would someday become the true king of Castle Grayskull by uniting both halves of the Power Sword to enter Castle Grayskull, claim its throne, and learn the secrets of the universe. In addition, the spirit informed Teela that she was fated to become the guardian of the castle. The evil wizard Skeletor desperately craved the power hidden within the ancient structure, but the spirit knew that He-Man was the prophesied warrior destined to become king of Castle Grayskull.

Castle Grayskull as it appears in the Masters of the Universe Cartoon

As in other canons, Castle Grayskull held ultimate power in the Filmation series. Additionally, however, it provided Prince Adam with the ability to transform into He-Man using the Sword of Power. The ancient structure was perched above the Abyss, which served as a moat, in the Evergreen Forest of Eternia. Furthermore, the Abyss appeared to be where the source of the castle’s power was housed. The lush foliage surrounding it helped obscure its location and kept the fortress hidden from would-be intruders. The powers of any who entered Grayskull were enhanced, whether good or evil. Grayskull’s drawbridge was referred to as the Jaw-Bridge, as it opened downward from the skull’s mouth and was lined with stony teeth. He-Man could cause the Jaw-Bridge to open by raising his sword and saying, “By the Power of Grayskull, I command the Jaw-Bridge open!” Others, lacking permission to enter, were forced to breach the castle’s defenses or, on one occasion, answer a riddle posed by the castle. Grayskull’s defenses could not be used against any who was a friend to He-Man.

Castle Grayskull’s protectors were a long line of Sorceresses, chosen by heritage or for their virtues. Each candidate would enter the Pool of Power, and only the wisest and gentlest would receive the Power of Grayskull. Among the many wonders within Castle Grayskull’s walls was a magical timer in its main chamber which used a circular pattern of lights to indicate the remaining time. The Window of Spirits allowed the Sorceress to communicate with other beings across dimensions. The Chamber of Light could cure many ailments. Castle Grayskull’s upper levels contained a laboratory; the Hall of He-Man, which was full of captured weapons from Eternia’s history; the Time Corridor; and a small hall of doors, behind which were kept many of the castle’s secrets. A large stone head inside the castle would test those who wished to obtain Grayskull’s power.