Eternia is a fictional planet in the Masters of the Universe franchise, created by Mattel. It serves as the primary setting for the adventures of characters like He-Man and Skeletor. Eternia is characterized by its diverse landscapes, including lush forests, deserts, and mountains, as well as its magical elements and ancient technology. The planet is home to various civilizations and creatures, often reflecting themes of good versus evil. Key locations include Castle Grayskull, a fortress that holds great power, and the Crystal Castle, which is associated with the Sorceress. Eternia's rich lore and vibrant characters contribute to its enduring popularity in pop culture.