All four Kings must be freed for the Dreamer's Door to open!
The four Kings – Carnivora, the Mocking Bird, El Stomacho and Creveton – are the rulers of the four lands that compose the Glade of Dreams in Rayman Origins. When Bubble Dreamer started having nightmares again, the Kings fell under their influence, and became gigantic, evil monsters. Rayman and his friends must track down these four monsters and defeat them. When they do, the monsters revert to the small, benevolent creatures they originally were, and begin projecting a ray of energy across the sea to the Dreamer's Door. These rays are focused by four nymphs, each of whom corresponds to one of the Kings. When the four Kings have been freed and enough Electoons have been collected, the Dreamer's Door opens, allowing the heroes to pass through to the Moody Clouds – the final land of the main game. In The Reveal, the final part of this land, the heroes must fight mechanical recreations of Carnivora and the Mocking Bird (neither of which are quite as powerful as the original).
In Mystical Pique, the level preceding and connected to Moody Clouds, the heroes encounter the Golem, an enormous stone monster whom they must defeat. He appears to be the ruler of his land, but does not seem to be counted as one of the Kings. When defeated, the Golem simply falls apart rather than reverting into a friendly character.
The Kings bear a certain resemblance to the bosses of the original Rayman, in that each boss is strongly associated with their own land, and reverts to a friendly state once they have been defeated. This may mean that the original game's bosses were corrupted by the influence of Polokus's nightmares, which were presumably the result of Mr Dark stealing the Great Protoon and imbalancing the Glade of Dreams. The Kings also resemble the Guardians of the four Masks of Polokus in Rayman 2, in that their number is four. The Kings are considerably smaller than most of the creatures that they rule, slightly resembling Gumsi, the king of the Knaaren from Rayman 3.