Seeking a new way to crush his old rival Sonic and conquer the world, Doctor Robotnik uncovers the legend of Chaos — a creature that, thousands of years ago, helped protect the Chao and the all-powerful Master Emerald. When a tribe of echidnas tried to seize the Emeralds' power and shattered the harmony of the land, Chaos retaliated, harnessing that power to become the monstrous Perfect Chaos and wiping them out. Before it could destroy the world, a young echidna named Tikal, who had befriended Chaos, sealed it — and herself — within the Master Emerald. Now Eggman has released Chaos once more, and Sonic and his friends must thwart his schemes and stop the beast from growing ever more powerful.