Chaos (カォス, Kaosu) is a video game character and the main antagonist in the video game Sonic Adventure for the Sega Dreamcast. Chaos is the first main antagonist of a Sonic game that is not Doctor Eggman. This eventually became common in the 3D games, with Eggman's role as the main villain being replaced by other villains (though often Eggman still makes an appearance). Chaos is an immortal, ageless god-like creature (referred to as the "God of Destruction" by Eggman) that seems composed almost entirely of water (save for his brain, green glowing eyes, and, in some later forms, bones) but is also said to be concentrated Chaos Emerald energy (in Sonic X, Doctor Eggman implies that it is composed of "Chaos energy in a liquid state"), however it has been revealed that Chaos is a Chao that came into contact with the Chaos Emeralds. It was trapped inside the Master Emerald for thousands of years before being released by Dr. Eggman in a bid to conquer the world. It was also the original guardian of the Chaos Emeralds, Chao, and the Master Emerald. In Sonic Adventure it absorbed the negative energy of the Chaos Emeralds to attain its final and strongest form.