Chaos is the main antagonist of the video game Sonic Adventure for the Sega Dreamcast. Chaos is an immortal, ageless, god-like creature that seems to be composed entirely of water, but is also said to be concentrated Chaos Emerald energy. It was trapped inside the Master Emerald for thousands of years before being released by Dr. Eggman in a plot to conquer the world. Chaos was also the original guardian of the Chaos Emeralds, Chao and the Master Emerald. In Sonic Adventure, Chaos absorbed the negative energy of the Chaos Emeralds to attain its final and strongest form, Perfect Chaos.