The top of the castle that houses the Dark Emperor. The King (Your Mii in the original game) is held in a hanging cage, waiting to be freed by noble fighters.
The Dark Emperor himself inflicts certain effects on the fighters depending on their color. For instance, red characters get a power increase. The stage itself has one large platform to the left and a smaller raised platform to the right. Either of these platforms can break. If you attack the cage with the Mii in it, the Dark Emperor will go away.