Masters of the Universe (movie)
Gwildor reveals that Skeletor has stolen his invention: a "Cosmic Key" that can open a portal to anywhere by using musical notes. This is how Skeletor entered Castle Grayskull. He-Man, Gwildor and the others travel to Castle Grayskull and try to defeat Skeletor. However, Skeletor's army overwhelms them and they use the Cosmic Key to teleport away.