Chaos/Pre-SGW

Chaos is a Chao that mutated into a water elemental, which was responsible for all but wiping out the Knuckles Tribe of Echidnas. Imprisoned in the Black Emerald by Tikal, a girl from that tribe, Chaos remained trapped for centuries until he was released by the maniacal Dr. Eggman. After accumulating power from various Super Emeralds, he attacked Station Square only to be stopped by Super Sonic. Following this, Chaos, Tikal and the Seven Server Chao he where protecting returned to their zone within the Black Emerald.

The Knuckles Clan
Exactly how Chaos came into being was lost to history: it is unknown whether it is a spirit that has always existed, a mutated Chao, or perhaps one of the Ixis Masterworks. Prior to becoming a legendary force of destruction, Chaos was the peaceable guardian of a group of Chao-all of whom it considers to be its children-living in the Mystic Ruins. He worked at this task for an unknown period of time, until he eventually met Tikal when the Knuckles Clan settled near his home. The two soon became friends despite Chaos' inability to speak and usual state as a pool of water, and for a time all was well. But as the war between the Knuckles Clan, the rival Nocturnus Clan, and the Felidae of the Mysterious Cat Country escalated, clan leader Pachamac sought to seize the seven Chaos Emeralds that belonged to Chaos' charges. When he and his warriors attacked, Chaos was corrupted by outrage and destroyed them, going on a rampage that might have spread to the rest of Mobius had Tikal and the Chao not been able to seal him inside the Black Emerald, putting an end to his threat-for a time. (StH: #82, CSE)

Release & Evolution
Chaos' legend fell into obscurity, and it was only as Dr. Eggman looked over the file network of his deceased counterpart Dr. Ivo Robotnik that he discovered Chaos' existence and began scheming to claim the creature's power for himself. Using an army of Robians, he excavated the Black Emerald from the midst of the Mysterious Cat Country, cracking it with a hammer blow only to discover that Chaos' imprisonment had weakened him. However, Chaos remained strong enough to lead Eggman to an ancient inscription that revealed to him that Chaos could be restored using the seven Super Emeralds created when the Chao imprisoned him and drained his powers, or by using seven Emeralds equally powerful. When Eggman shattered the Master Emerald into pieces to see his goal fulfilled, a part of Chaos' substance landed in the Mysterious Cat Country and was swallowed by Froggy. Eggman was able to help Chaos on his first step towards recovery by using shards from the Master Emerald as well as Froggy's now-altered DNA to restore some of Chaos' strength. (StH: #79, #80, #81)



Thus fortified, Chaos infiltrated the Hidden City of the Ancients and soon became involved in a battle with the local police. He was then challenged by Sonic the Hedgehog, who defeated him as he was in a weakened state. Later, Chaos attacked Sonic, Miles "Tails" Prower, and Knuckles the Echidna, stealing from them Master Emerald shards and two Super Emeralds in order to evolve into his next form. However, Chaos still proved no match for the three, and was once against defeated and forced to retreat with Dr. Eggman. (StH: #82, SSS: #13)

Chaos was once again able to evolve while on board the Egg Carrier, after Eggman stole two Super Emeralds from Big the Cat. With this new form, Chaos nearly drowned Knuckles within himself, but Sonic managed to freeze Chaos by throwing two of Eggman's Ice-Bots into him. Sonic and Knuckles both shattered the frozen Chaos, which caused a chain reaction and resulted in the Egg Carrier's destruction. Sonic and Knuckles collected the Master Emerald shards and Super Emeralds and fled, while Chaos managed to escape by sticking to Eggman's flying pod. (SSS: #13)

At this point Chaos began working on his own without Eggman. Knocking both Eggman and Knuckles out, Chaos proceeded to absorb the Super Emerald in Tails' bi-plane, which Big the Cat had crashed while escaping from the Egg Carrier. Chaos then broke into Station Square's power plant and absorbed the other six Super Emeralds which had been collected, thus transforming into Perfect Chaos, upon which he launched a devastating assault on Station Square. (StH: #83)

Perfect Chaos vs. Super Sonic
Perfect Chaos flooded the streets of Station Square, forcing the Knothole Freedom Fighters and their ally Nate Morgan to work quickly in order to save many citizens. For all their valiant efforts, they could not deal with the creature themselves, and even Sonic and Knuckles were at a loss. Dr. Eggman returned with a second Egg Carrier, intent on reclaiming Chaos for himself, only for Perfect Chaos to betray him once again and blast his ship out of existence. Tikal then arrived and shared with Sonic a vision of Chaos's past, helping him to understand the threat posed by the creature. Using her powers, Tikal removed the Super Emeralds from Perfect Chaos, delivering them to Sonic so that he could use them to seal Chaos within a restored Master Emerald. Drawing on the untouched positive energy of the Emeralds to combat Chaos' negative power, Sonic transformed into Super Sonic and engaged the massive creature. (StH: #83)

For all of Super Sonic's power, though, he found himself in a deadlock with Perfect Chaos, unable to weaken him enough to bring him down. While the two titans clashed, Knuckles set about finding a way to short-circuit Perfect Chaos so as to defeat him once and for all. Using his immense strength to lift an entire power plant, Knuckles restored its connections and set electricity flowing just as Super Sonic led Perfect Chaos into the midst of the electric wires. Chaos reverted back to his original state, seemingly also made peaceable again as the Super Emeralds transformed back into the Seven Server Chao. Tikal then used her magic to teleport herself, Chaos and the Seven Servers back to their zone within the Black Emerald, where they resumed a life of peace. (StH: #84)

Merged with a Devil

 * See also: Chaos Devil

Over a year later, Mobius was rewritten by the second Genesis Wave. This created an altered timeline in which Chaos had been previously pitted against Sonic, who, a lot like before, successfully defeated the former with the help of Tikal. Much later, Chaos was reawakened again by Dr. Eggman and was merged with Dr. Wily's Devil Core to create the Chaos Devil. The monster was accidentally unleashed by Rouge the Bat aboard the Wily Egg during her attempts to bring down the ship from within. It managed to capture Rouge and Metal Sonic v3.0 and was menaced by Bass, but the two doctors arrived and ordered it to release its captives. It did so, and Rouge was taken away to be roboticized, while the doctors prided themselves on the success of the Chaos Devil's operation. It later appeared again to engage Sonic and Mega Man as they made their way deeper into the Wily Egg, but was engaged by the heroic robot Duo. After a heated battle, Duo freed Chaos from the Devil Core and destroyed it, and the pair were then caught up in the effects of the Super Genesis Wave. (MM: #27, SU: 53, StH: #251)

Powers
As a being composed of pure water, Chaos had the ability to elongate his body to attack enemies from a distance, as well as to change shape in order to dodge attacks or fit in narrow spaces. By absorbing Super Emeralds or similar objects of power, he has the ability to evolve into progressively stronger incarnations of himself, each differentiated from his original form of Chaos 0 by a number from one to seven, the seventh also being known as Perfect Chaos. Chaos can also manipulate water to a great degree and use it to attack enemies.

Background Information

 * Chaos's appearance in the comic in the original continuity mirrors that of its appearance in the game Sonic Adventure. However, certain important events from the game were changed to match up with the comic universe during its initial adaption:
 * Instead of being sealed in the Ancient Onyx (The Black Emerald), Chaos was instead sealed in the Master Emerald itself; this change was necessitated by the fact that the Master Emerald had only recently been created in the comics as opposed to its ancient game origin.
 * Chaos was released when Eggman shattered the Master Emerald in Sonic Adventure, which he would also do in the comic, but only to help Chaos regain power with its broken shards.
 * In the comic, Chaos would transform when it absorbs each of the seven Super Emeralds, while in the game, it transforms from absorbing the normal Chaos Emeralds (there are only 7 emeralds in the games, while the amount of emeralds in the comic at the time was unlimited, though later the amount would become 7).
 * In the comic, Chaos would transform into Perfect Chaos when it broke into the Station Square power plant and absorb the 6 already collected Super Emeralds, while taking the 7th from Tails's crashed bi-plane. In the game, it takes the 7th emerald from Tails' plane just as in the comic, but instead gets the other 6 Chaos Emeralds from the alter of the Master Emerald.
 * These changes no longer apply in the post-Super Genesis Wave timeline, where it's assumed events played out more or less exactly as they did in the game.