Chaos

Chaos (カオス) is the main antagonist of Sonic Adventure. Chaos is an immortal, god-like creature composed entirely of concentrated, water-like chaos 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.

Past
Chaos was originally a normal Chao, but prolonged exposure to the energy of the Master Emerald caused it to mutate into a strange water-like creature. It used its new powers to guarantee clean water around the altar of the Master Emerald, and to protect its fellow Chao. However, about four thousand years ago, the leader of the Echidna tribe, Pachacamac, attempted to steal the Emeralds for use against his enemies. Tikal, his daughter, resented this idea, worrying that it would upset Chaos and it would bring wrath to them, but Pachacamac did not want to hear it. His warriors stormed the shrine, where the Emeralds reside. Many Chao were injured in the process, as was Tikal herself. Chaos, in a fit of rage, absorbed the negative power of the seven Chaos Emeralds, and transformed into Perfect Chaos. As a result, it became a massive water creature. Floods destroyed the civilization, and Chaos avenged its Chao brethren. In order to prevent Chaos from destroying the world, Tikal linked her consciousness with Chaos' via a prayer, and sealed them both into the Master Emerald. It is probably at this point in history that the Emeralds were first called the "Chaos Emeralds".

Sonic Adventure
Chaos lay dormant in the Master Emerald for thousands of years until Dr. Eggman, having read ancient tablets describing the fall of the Echidnas and Chaos, released it by shattering the Master Emerald. Chaos swore to follow Doctor Eggman as it knew that he could get the Chaos Emeralds back for it. Sonic the Hedgehog eventually encountered Chaos as it was attacking a building and several Police officers, and easily defeated them. Because of its appearance, Sonic initially referred to it as "big drip."

Eventually, Eggman's plans, as always, fell through at the hands of Sonic and his friends. Chaos eventually abandoned Dr. Eggman, destroying his Egg Carrier in the process, and collected the Chaos Emeralds for itself. Once they were in its possession, it absorbed the negative powers of the Emeralds once again and transformed into Perfect Chaos to destroy Station Square in a rage. Having only taken the negative energy, Chaos discarded the remnants of the Chaos Emeralds. This proved to be the means to Perfect Chaos's downfall as Sonic absorbed the positive energy of the Chaos Emeralds and transformed into Super Sonic, eventually defeating it and in the process, its evil mindset was returned to its regular state and changed back to its original form. Tikal then approached Chaos, and together they disappeared in a flash of light. Though its whereabouts are unknown, it is presumed that Chaos returned to watching over the Chao with Tikal.

Sonic Battle
Chaos 0 also appears in Emerl's story in Sonic Battle, where it can be challenged. After the player defeats Chaos, it is unlocked as a playable character in Battle and Challenge modes. In-game, Chaos can barely jump and is incredibly slow but its extendable limbs give it a much wider attack range than it appears to have, and has the highest attack power in the game. It can turn into a puddle of water as usual, and can create fountains, tentacles, and orbs of water.

In the story of Sonic Battle, Knuckles the Echidna claims that Chaos appears when there is an upcoming disaster. When Dr. Eggman threatens the Earth with his Death Egg in the final story, a nearby volcanic crater is flooded, and Chaos emerges. It can then be challenged by the player.

Sonic Generations
Perfect Chaos reappears as the iconic boss of the Dreamcast era in Sonic Generations. Sonic fights Perfect Chaos without his Super State, relying on boosts and Homing Attacks to defeat the creature.

Its appearance differs greatly from Sonic Adventure: Chaos appears to have darker reptilian scaled skin, green horns and teeth, and its body doesn't seem to be made completely out of water as with its previous appearances. Chaos' upper body is solid and the lower body is liquid. It has been explained that this was what Perfect Chaos was originally meant to look like (however, due to technological restraints it was not possible at the time). This design of Chaos is actually seen in Sonic Adventure, on the mural in the Lost World stage.

Sonic Forces
In Sonic Forces, when Dr. Eggman discovered the Phantom Ruby, he tested its power on Angel Island, creating an physical illusion of the village of the Knuckles Clan. A part of this restoration, Chaos emerged from the Master Emerald to fight Knuckles the Echidna and Silver the Hedgehog. However, it disappeared as soon as Knuckles and Silver defeated it.

Chaos, alongside Metal Sonic, Shadow and Zavok, was soon after replicated by Infinite, Eggman's newest servant, using the virtual reality powers of his Phantom Ruby. This replica was instated in the Eggman Army as one of the group's foremost soldiers. The Chaos replica soon after made its debut alongside the other three replicas to assist Infinite in defeating Sonic. Afterward, the Chaos replica helped Eggman conquer over 99% of the world.

Six months later, the Chaos replica attempted to ambush Tails in the City while he was repairing E-123 Omega. Before it could attack Tails though, it was defeated by Classic Sonic when he emerged from a wormhole. Hundreds of replicas of Chaos were later present in the outskirts of the Eggman Empire Fortress where they took part in the final battle between the Eggman Army and the Resistance until the Phantom Ruby was destroyed for good, ending the replicas' existence.

Sonic Adventure 2
In Sonic Adventure 2, Chaos is a playable character in the multiplayer treasure hunt mode, unlocked in the Dreamcast version by getting A Ranks in all of Rouge the Bat's missions, and available at the start of the GameCube version. In this game, Chaos has the ability to glide and dig in the same way as Knuckles and Rouge. He moves slower than the other characters, but his special attacks hit harder with longer-lasting effects. On the Dreamcast version however, he borrows his special attacks from Rouge. Its brain is not visible in this game.

Sonic Heroes
Chaos did not appear in Sonic Heroes, but was mentioned in two lines, at the ending of Team Rose's story, when Froggy and Chocola are rescued, Metal Sonic says: "Chaos data...has been copied." At the final story, where Dr. Eggman says, "It's hopeless! Metal Sonic has combined your data with the power of Chaos and is super strong!" He copied Chaos' data from Big's frog, Froggy, since he was "possessed" by Chaos's tail, along with Chocola the Chao, since all Chao have some kind of relation with Chaos.

Super Smash Bros. Brawl
In Super Smash Bros. Brawl, Chaos appears as a Sticker:

Sonic Chronicles: The Dark Brotherhood
Chaos did not appear in Sonic Chronicles: The Dark Brotherhood, but played a significant part in the game's backstory. It was mentioned that because Chaos caused the destruction of the Knuckles Clan, it allowed the Nocturnus Clan to reign supreme in the ancient world, before they were drawn into the Twilight Cage, as it had wiped out the Nocturnus Clan's most prominent opponent. It was also mentioned in one line, when Knuckles realized that Shade was an echidna. Here, he revealed that Perfect Chaos flooded an ancient city and killed several hundred echidnas that resided there.

Sonic and the Black Knight
In Sonic and the Black Knight, the name "Chaos" appears as one of the default names when starting a profile.

Mario & Sonic at the Olympic Winter Games
Chaos appears, as an ice version Perfect Chaos, in Mario & Sonic at the Olympic Winter Games as an obstacle in Dream Figure Skating (Sonic World). He also appears in his normal form as a VIP character that will sometimes send you letters and as a sticker.

Sonic Forces: Speed Battle
In Sonic Forces: Speed Battle, Chaos is a playable character who was added to the game's roster in the version 1.0.1 update. He has the following stats that are applied in gameplay:

Personality
Before Tikal's father and his soldiers came to the place where Chaos and the Chao lived, Chaos was a very loving and gentle creature, being very protective of the Chao and possibly Tikal. But after the Chao that Chaos guarded were injured, Chaos became evil minded and furious at other beings and became completely consumed by anger and rage. When unleashed in the present time, it wanted nothing more than to destroy the world once more, even assisting Doctor Eggman in collecting the Chaos Emeralds to ensure such. However, when Super Sonic neutralized it, Chaos returned to its previous peaceful and gentle demeanour.

Powers and abilities
Chaos is an incredibly strong creature whose power is so great that it is revered as a god of destruction. Even at its weakest, Chaos is said to possess immeasurable powers.

Chaos possesses the ability to absorb Chaos Emeralds and its form, power and skills change and increases with every Chaos Emerald that it absorbs, until it reaches a fully realized Super transformation. Over time it develops from a humanoid water creature to a horrible, world-destroying monster. Because of its liquid-like appearance, it is also immune to bullets and gunfire.

Chaos 0
In its basic form, Chaos 0 can use his extendable arms that are fueled by energy, to attack his opponent. He is also very agile, being able to jump several tens meters. His body is also bulletproof, due to being a liquid being consisting of chaos energy. He is capable of limited shapeshifting, so he can be in a drip form, that he uses to escape. Chaos 0 is very potent fighter as he could take on Knuckles the Echidna, who is master of martial arts.

Chaos possesses a variety of special attacks, used only by itself. It can deliver a powerful ground punch that creates a small earthquake, releasing a blue energy pulse that harms and confuses enemies, and finally freezes the air around the enemy for thirty to forty seconds. Chaos has some skills of a treasure hunter, that he can search for Emerald shards, or anything else. Being a liquid being, enables it to swim indefinitely.

Chaos 1
After Chaos absorbs one Chaos Emerald, Chaos has slightly changed. Chaos 1 increases in size and gains a line of "bones" that travel down its right arm into its hand, where the Emerald is located. As such the arm becomes bulkier. He briefly appears in Sonic Adventure after Sonic or Tails fights Eggman for the first time, and is never fought. Due to never being fought, his abilities are unknown. Knuckles also meets Chaos 1 in the Hotel room just before it transforms into Chaos 2.

Chaos 2
Chaos is much stronger after absorbing the two Emeralds. It is taller and more muscular. It has also developed new powers like a blue energy shield to prevent frontal attacks and the ability to transform into a huge ball, several small orbs, or waves of water.

Chaos 4
Chaos' shape is transformed to a shark-like water creature that can swim and dive into water. It can split itself into projectiles just like Chaos 2, however it is upgraded with new abilities to match the new form, including more control on water and nimble leaps that create waves of water toward the opponent.

Chaos 6
After absorbing six Emeralds, Chaos has changed dramatically once again. It is no longer even vaguely humanoid, but a scorpion/spider/frog-like creature. Chaos now commands more energy to empower his body, and also use his retained tail to smash opponents.

Perfect Chaos
After absorbing the negative energy of all seven Chaos Emeralds, Chaos will become a giant serpentine dragon-like beast with a mouth extending far beyond its eyes, which for the first time have pupils that resemble a reptile's. At the base of its snake-like body seems to be a huge whirlpool and cyclone. It has large tentacles extending from its base.

Perfect Chaos' new powers include creating small tornadoes, firing clusters of yellow and pink energy balls, and shooting a powerful energy beam from its mouth. It has complete control over water as Perfect Chaos is able to flood Station Square with ease.

Archie Comics
The Sonic the Hedgehog comic series echoed the Sonic Adventure storyline, with a number of variations. Chaos and Tikal were both imprisoned in a Black Emerald, which was broken open by a hammer wielded by Dr. Robotnik. This continuity also featured the Freedom Fighters, who assisted Sonic and Knuckles in the victory over Perfect Chaos. Chaos was later featured in the Worlds Collide crossover, the events of which led to an altered continuity in which the events of Sonic Adventure apparently occurred in the comic universe in exactly the same way as in the game.

Sonic X
The Sonic X anime follows the plot line of Sonic Adventure in episodes 27-32, resulting in Chaos's presence in those episodes in several of his forms. Here, he is described as "energy in a liquid state" rather than the "God of Destruction" in the English dub of the anime. He also made a few appearances in the Sonic X comic series published by Archie Comics.

Reception
Despite the fact that its main appearances were in three main series games, Chaos has become one of the most popular Sonic characters and has ranked as ninth in an official poll, sitting between Metal Sonic in eighth place and Rouge in tenth.

Theme songs
Chaos has a number of theme songs in the games that are attributed to itself. The genres of the songs vary.
 * "Boss: Chaos ver.0, ver.2; ver.4" - plays during the battles against Chaos 0, 2 and 4. It is also used in Super Sonic's story summaries as there is an image of Perfect Chaos in the backdrop.
 * "Boss: Chaos ver.6" - plays during the battles against Chaos 6.
 * "Perfect Chaos Revival" - plays during the second half of the battle against Perfect Chaos. It also plays in Mario & Sonic at the Olympic Winter Games when Perfect Chaos appears.
 * "Open Your Heart" by Crush 40 - plays during the first half of the battle against Perfect Chaos; shared as the main theme of Sonic Adventure. A cut-down, instrumental version is also used in Mario & Sonic at the Olympic Winter Games.
 * A special song plays in the fight against Chaos 0 during the Story Mode of Sonic Battle. It has no name, but is number 18 in the Sound Test.

Trivia

 * In Greek mythology, Chaos was the name of the first deity to come into existence. It is described as vast and formless, much like the being from the Sonic series. According to Hesiod, Chaos was also the dark void from which the Earth goddess Gaia was born.
 * Although Chaos first appeared in Sonic Adventure, he was briefly alluded to as early as the prologue in the manual for the Japanese version of Sonic the Hedgehog 3, where Knuckles speculated that the crashed Death Egg in the lake on Angel Island was the egg containing a legendary dragon that was fated to destroy the world.
 * Because of positioning on the map, Big the Cat is able to come in contact with Chaos 4 prior to his battle with Chaos 6 by approaching the arena from the proper direction and jumping into it. This is the only time that directly touching Chaos does not harm a character.
 * In Sonic Adventure and Sonic Generations, Chaos is translucent, but in all his other appearances he is opaque.
 * Chaos 1 is the only seen form of Chaos not to have a boss.
 * Chaos 1, 2, 4, and 6 have what appear to be bones, but Perfect Chaos does not have any. The bones are probably meant to hold the Chaos Emeralds in place until he has all seven of them.
 * Chaos 3 and 5 are never seen, as Eggman gives Chaos the third and fourth emerald at the same time and he gives the fifth and sixth emerald to him off-screen.
 * When the Chaos Emeralds are in Chaos, they look like a gradient color tint rather than their usual diamond design. Additionally, the emeralds that appear inside Chaos are rarely the same color as the actual Emeralds he has received; his second Chaos Emerald, the Gray Emerald, appeared Red once he had absorbed it.
 * Chaos was purposefully created for Sonic Adventure to be a boss that would have been difficult to render on systems before the Dreamcast.
 * In Sonic Adventure 2, Chaos is featured on several billboards. First, billboards advertising two fictional soft drinks (Chaos Cola and Chaos Soda) appear in several stages, such as Shadow's Radical Highway stage. Second, in City Escape and the Big Foot boss battle, Chaos 0 can be seen on billboards advertising a fictional movie named Planet of the Chaos, apparently based on Planet of the Apes. The movie is shown to be rated PG-13 by the MPAA.
 * There is a special kind of Chao, called the Chaos Chao, whose head and limbs resemble those of Chaos 0.
 * Chaos and Chaos Gamma are the only playable characters in Sonic Battle that do not have a story mode.
 * They are also the only unlockable playable characters in Sonic Battle.
 * Chaos was intended to be in Sonic Heroes in a team with E-102 Gamma and Big. This is likely why Chaos and Gamma appeared in Sonic Battle instead of Omega or the Chaotix.
 * According to an interview on Sonic Central, Sonic does not know the whereabouts of Chaos, Fang the Sniper, Bark the Polar Bear, Ray the Flying Squirrel, Bean the Dynamite, or Tikal.
 * Chaos appears as the final boss in the Sonic the Hedgehog Level Pack of LEGO Dimensions. In this game, a giant Chaos 0 from another dimension attacked the Death Egg seeking the Chaos Emeralds, where it fought Sonic the Hedgehog until Sonic could go Super Sonic and defeat the beast.