"In Rayman's world, nature and people live together in peace. The Great Protoon provides and maintains the harmony and balance in the world" - The Magician
The Great Protoon is an important part of the world in the original Rayman game, maintaining the peace and harmony of the world. When it is stolen by Mr Dark, the world becomes unstable and evil beings start to appear and capture the electoons.
The Great Protoon serves the same purpose as The Heart of The World mentioned in later games and may be the same entity.