Castle Grayskull is a fortress located on the fictional planet Eternia. It forms a central location in the Masters of the Universe toy/comic/animation universe and also appears in the 1987 live action adaptation. The concept is credited to Donald F. Glut. The toy set was invented by Roger Sweet. Castle Grayskull was a "major feature of Mattel's line", and was "one of the most famous playsets of all time".
