Chaos

Name: Chaos
Nickname:The God of Destruction
Age:Anchient (true age unknown)
Species:Water lifeform

First Game:Sonic Adventure (Dreamcast)

Chaos once guarded the Master Emerald and the Chaos Emeralds long ago. He also guarded the Chao and became a bit of a friend with Tikal.

When Tikal's father, Pachacamac, tried to take the Chaos Emeralds for power and hurt all the Chao Chaos was enraged. He used the power of the Chaos Emeralds to transform himself. To prevent him from destroying the world Tikal sealed him along with herself inside the Master Emerald.

Centuries, maybe even millineums later Chaos was released by Doctor Eggman, shattering the Master Emerald in the process. Eggman tried to use Chaos to conquer the world. Whenever Chaos got a Chaos Emerald he transformed and became more powerful. Sonic and Tails tried to prevent him from getting all the Emeralds, but to no avail.

Chaos got the seven emeralds and transformed into Perfect Chaos, a giant water monster. However Chaos only used the negative power of the emeralds. Sonic used the positive power to defeat Chaos and also defeat the anger in Chaos. After that Chaos and Tikal departed.

Metal Overlord copied Chaos's power in Sonic Heros.