The story of Chaos dates back to a time before Knuckles was born. Thousands of years ago on the mysterious Floating Island ( known to it's inhabitants as Angel Island. ), The Echidnas crafted a sound civilization built around the protection of the Chaos Emeralds, powerful gems with magical properties. The Echidna civilization's most valued possession, The Master Emerald, kept the Island afloat with magic, & was safely held within an altar, guarded by the Echidna chief, Pachacamac ( Or Pacha for short! ) & visited frequently by the chief's daughter Tikal.
Surrounding the altar was a lake where the childlike creatures known as Chao often played. One day, a Chao got a bit too close to the Master Emerald, causing the creature to magically transform into the peace-loving being you see above! Born from the Emerald's power & the enchanted lake, this creature acted as a guardian of sorts to the Chao, hidden away by Tikal for fear of it being seen as a monster to the other Echidna. Unfortunately,Tikal's fears manifested on one horrific night.
Pacha and his men attacked the creature, giving it the name Chaos, & enraging it until it rampaged all of Angel Island as The God of Destruction. The rage it felt, fused with the Master Emerald's power, turned Chaos into a monstrous abomination. Fortunately, Tikal quelled the beast, sealing it within the Master Emerald where no one could hurt it again.
Since then, Chaos has been released by Dr. Eggman once already, causing a massive flood that would've destroyed Earth had Sonic & Co. not stopped him. Chaos is a creature of peace whose power is constantly manipulated by those with villainous intent. & once again, it seems the mad doctor has plans to release the entity & unleash it's power with nothing but pure vengeance.