Chaos Emerald


 * For other uses of the term, see Chaos Emeralds (disambiguation).

"The servers are the seven Chaos... Chaos is power, enriched by the heart... The controller exists to unify the chaos!"

- Tikal the Echidna

The Chaos Emeralds (カオスエメラルド) are seven ancient relics of great power from the Sonic the Hedgehog series video games. The Chaos Emeralds have mystical properties and abilities, and the holder of them all can use them for a large variety of things, such as creating a powerful super transformation, powering machines, and warping time and space. Due to the immense powers they possess, they are usually the target of villains, who desire them to fuel their own evil ambitions, and of heroes, who want to keep them away from the villains and use them for good. After the conclusion of a story, the emeralds tend to scatter themselves, and as such characters often collect them throughout the games. While they were more like "bonus" items in the early games of the series, the Chaos Emeralds became necessary plot devices in Sonic Adventure, and that trend has continued throughout the later 3D games.

Background
The Chaos Emeralds' background is shrouded in mystery, and they are known to have existed for millennia along with the larger Master Emerald. The emeralds' power has been passed down into legend, and the power of all seven Chaos Emeralds brought together has been described from the emergence of a mysterious power to nothing short of a miracle. It is said on many occasions that those whom manage to obtain all seven Chaos Emeralds would gain ultimate power.

While it remains unknown when, how and possibly why the Chaos Emeralds were created, it is known they predate the Master Emerald, which has existed since before recorded history, and that they have played a large role in numerous different civilizations and events throughout known history. It has been revealed that ancient civilizations such as the Echidnas and the Babylonians that existed thousands of years prior to the games knew about the Chaos Emeralds, along with the Black Arms, who have visited Earth for at least 2,000 years. The Nocturnus Clan who existed over 4,000 years prior to the games have also been known to have been experimenting with the Chaos Emeralds. The emeralds also have a connection to the Gaia Temples, which are supposed to go back ten thousands of years.

It is said that in the far ancient past, the Chaos Emeralds were used for many evil puposes. When the gods witnessed this misuse, they created the Master Emerald to control the Chaos Emeralds and balance out their power. Over 4,000 year prior to Sonic Adventure, the Chaos Emeralds had come to rest at the Emerald Shrine with the Master Emerald on what would become Angel Island for an unknown amount of time. It is known that even in these ancient times, the emeralds and their power was well known and revered throughout the world. Due to this, the leader of the Knuckles Clan, chief Pachacamac and his followers tried to take the emeralds to gain undisputed power, but in the process they angered the guardian of the Emerald Shrine, Chaos, who used the Chaos Emeralds to destroy their civilization in vengeance, before being sealed in the Master Emerald by Tikal. This also marked the earliest known use of the Chaos Emeralds. After this event, the emeralds were named Chaos Emeralds by the remaining echidnas due to their connection with Chaos, and have since been primarily guarded by the echidnas.

According to Sonic Adventure, the ancient saying associated with the Chaos Emeralds and the larger Master Emerald is "The servers are the seven Chaos. Chaos is power, power is enriched by the heart. The heart is the controller. The controller serves to unify the Chaos." The meaning of this saying is further clarified in Sonic Adventure 2 by the Master Emerald's power to neutralize the Chaos Emeralds, and in Sonic the Hedgehog where their ability is described as being able to "transform thoughts into power." While the Chaos Emeralds can lie around basically anywhere, they can quite often be found in Special Stages (also known as "The Special Zone"), strange alternate dimensions. Even alone, their power is unmatched by pretty much anything else in the universe, except perhaps by the Master Emerald, which is just as powerful as all seven Chaos Emeralds, if not more, the Wisps' Hyper-go-on energy and the Power of the Stars.

The Chaos Emeralds in themselves are usually used for laser radii or nuclear-based weapons of mass destruction (in Doctor Eggman's case), Chaos Powers (normally the case with Shadow the Hedgehog), and letting people turn into their Super States.

Powers and Traits
Each Chaos Emerald is said to possess mystical properties and contains unlimited amounts of highly potent and powerful Chaos Energy that is said to give life to all things. The main power of each Chaos Emerald is described as being able to “transform thoughts into power”, implying they have some form of reality-warping capability. This allows them to perform certain feats, such as showing visions, perform rituals and even revive the recently deceased. Foremost, however, this power allows the Chaos Emeralds to generate the Chaos Energy they contain, making it the source of the emeralds vast energies. This makes the Chaos Emeralds an everlasting source of pure energy and enables them to float in the air by themselves. This energy can be harnessed from the Chaos Emeralds, either by their wielders, or machinery and can be used for various purposes. This energy can even be drawn and reacted from the emeralds without physical contact and be done so over great distances, but they still have to be in close vicinity to the user.

When someone harnesses the power of one or more of the Chaos Emeralds, they can perform different Chaos Powers, such as Chaos Control, and occasionally get their own abilities enhanced. When absorbing all seven Chaos Emeralds, they can initiate a super transformation, which allows a person to enter a Super State, an enhanced form that grants the person flight, near invulnerability, different Chaos Powers, and drastically increases physical and innate abilities. These transformations, however, do not last long, as they quickly consume energy and require ring energy to be maintained over longer periods of time. The energies of these super transformations can also be given from one Super State to another character to allow that person to achieve a Super State of their own (for example, at the end of Sonic Heroes and Sonic the Hedgehog (2006)).

The energy of the emeralds can also be harnessed to power machines, making it possible to power various types of powerful and advanced machinery that normally would be impossible to use, due to the immense amounts of energy they require, such as the Eclipse Cannon.

The type of Chaos Energy the Chaos Emeralds can produce is based on thoughts/emotions. Positive thoughts, such as friendship and caring, generate positive energies, and negative thoughts, such as anger and hatred, generate negative energies. If the Chaos Emeralds is absent of the negative energies (or possibly positive energies) as seen in Sonic Adventure, or all of their energy as seen in Sonic Unleashed, the emeralds will become gray, pale, and apparently powerless. The only known ways to restore the emeralds from this state is through peoples' thoughts, or the Gaia Temples.

The Chaos Emeralds also appear to amplify their own power the more emeralds there are used in the process. This is mainly demonstrated with the Eclipse Cannon: with five emeralds it could destroy a large city, with six emeralds it could blow up half of the moon and with all seven emeralds it could destroy planets and pierce stars.

Each Chaos Emerald is linked to each other, and as stated by Tails, Eggman and Eggman Nega, they act like magnets that can attract or repel each other, giving them magnetic characteristics. This for example allowed Tails to pinpoint Dr. Eggman's location on Space Colony ARK because he had the rest of the Chaos Emeralds in his possession.

Because of the great amounts of power emanating from each emerald, creating radars to track them is relatively simple (Rouge, Tails, and Dr. Eggman all had one in Sonic Adventure 2, and Tails used one again in Sonic Riders).

Collecting
For unknown or unexplained reasons, after the Chaos Emeralds have played their part in the story in the games, the users of them apparently lose possession of the emeralds, and they have to be collected in the following game, be it either from different places in the world, or different dimensions called Special Stages.

Although Sonic is seen at the end of the first Sonic the Hedgehog game allowing the Emeralds to return to their original places, it is unknown why the Chaos Emeralds need to be collected at the beginning of every game (except, of course, for the purpose of game dynamics).

However, there is one exception to this explanation. During the opening sequence for Sonic the Hedgehog 3 (if the player chooses Sonic alone or both Sonic and Tails as his/her character choice), Sonic is in possession of all seven of the Chaos Emeralds at the beginning. This is evident when he leaps off the Tornado and falls off-screen only to come racing across the ocean as Super Sonic before making his way onto Angel Island. There, Knuckles steals the Chaos Emeralds and hides them from Sonic so that he has to search from scratch like all other games. In the first season of the anime series Sonic X, Sonic states that every time they come together they always scatter again. Thus, another explanation could possibly be that Sonic himself hides them so their power won't fall into the wrong hands, and so all of them won't be in one group for "easy picking." This is also backed up by the Sonic X series in its final season where Sonic scattered the Chaos Emeralds throughout the universe while he was in his Super form so the Meterex wouldn't get a hold of them.

Another reason why the Chaos Emeralds are spread is because they have magnetic qualities as stated earlier; after each use of the Chaos Emeralds, the resulted merge of the emeralds and their power forces them to repel themselves from their shared location, so they tend to scatter themselves after each use.

Early Appearances
Throughout most of the early games, Doctor Robotnik tries to get his hands on the Chaos Emeralds in order to fuel his doomsday weapons. The player can choose to collect the Emeralds in their Special Stages in order to unlock a "good ending", a Super State, or both. The Chaos Emeralds have gained a more important part of the plot in later games.

Sonic Adventure
In Sonic Adventure, the Chaos Emeralds were collected by Eggman in order to feed Chaos, the guardian of the Chao and Emeralds, and it changed form every time it received one of the gems. With all seven, it became Perfect Chaos, and used up all of the negative energy in the Emeralds before dropping the powerless and dull emeralds onto the ground. Sonic then picked all seven up and used the positive energy to become Super Sonic and destroy Perfect Chaos. Also in the game, Tikal the Echidna states that "The 7 Emeralds can change our thoughts into power", and that the Master Emerald controls that power.

Sonic Adventure 2
In Sonic Adventure 2, Sonic and Shadow had the ability to use the Chaos Emeralds to utilize "Chaos Control", an ability that alters time and space to teleport or freeze time. Interestingly, Sonic, at one point, uses the Chaos Control ability with a fake Emerald that had the same wavelengths and properties as a real one. Shadow told Eggman to collect a few Chaos Emeralds in order to get enough power for the Eclipse cannon. In the end side Eggman had six Chaos Emeralds and he was able to destroy half the moon.



Tails soon managed to produce a "fake Chaos Emerald" that Sonic used in order to teleport back to the Space Colony ARK when Eggman sent him to space in an explosive capsule. Eggman stole the real emerald from Tails and put into to the Eclipse Cannon; however, when all seven were collected, the ARK started to fall toward Earth in order to kill millions of innocents for vengeance of Gerald Robotnik. The Chaos Emeralds were disabled by Knuckles, who used the Master Emerald, but when it appeared to be useless, as Biolizard was controlling the ARK, Sonic and Shadow used the emeralds to transform into their Super States for the last battle.

Sonic Advance series
The Chaos Emeralds play the same role they did in the classic games being only used to get a better ending and extra stage for Sonic.

Sonic Heroes
In Sonic Heroes, the gameplay pays homage to classic elements, so it goes back to a way of collecting the Chaos Emeralds in special stages to unlock the Last Stage. In that stage, Sonic becomes Super Sonic, and he gave some of his energy to Tails and Knuckles, giving them Super Shields.

Shadow the Hedgehog
In Shadow the Hedgehog, the Emeralds were found throughout the stages (again, Special Stages weren't used), and Shadow collected all seven by the end of the game, only to let them be stolen by the evil alien Black Doom, who used a superpowered Chaos Control to bring the Black Comet to Earth's surface. Shadow then got the Chaos Emeralds back and transformed into Super Shadow in order to destroy Black Doom and teleport the Black Comet into space to be destroyed by the Space Colony ARK's Eclipse Cannon, the cannon itself using the Chaos Emeralds as its power source.

Sonic Rush
In Sonic Rush the Chaos Emeralds are necessary to access the final stage of the game. Special Zones make a return as a way to find the Emeralds. The Emeralds are shown to have an inter-dimensional counterpart, the Sol Emeralds, with similar powers. The Chaos and Sol Emeralds' powers are shown to come from the positive emotions of their wielders in this game and they are used by both Sonic and Blaze to transform into their Super States.

Sonic the Hedgehog (2006)
In the 2006 game Sonic the Hedgehog, the Emeralds fully take on the power to "transform thoughts into power", just as the Master Emerald was said to be capable of doing in Sonic Adventure. These emeralds appear slightly smaller in size, and give off gleaming sparks of light of their respective colors, and are given the additional title of "miracle gems".

In the tiant and seal the newly born Iblis into his daughter's soul, so long as she abstain from crying, with the only other stipulation being that the vessel must be of royalty. Mephiles succeeds in mass-producing duplicates of himself using two Emeralds, and showing Silver a fabricated vision of a smug-looking Sonic surrounded in flames, through the Emerald itself.

Only six of the Chaos Emeralds appeared in this game: the green emerald (which Shadow and Rouge found whilst exploring Crisis City in the future. They then used it along with the cyan emerald to go back to the present while Shadow stayed in the future to battle Mephiles. Rouge then gave the Chaos Emerald to E123-Omega to give to Shadow in the future so as to escape Mephiles. Mephiles later used its power along with the yellow emerald to battle Shadow), the blue emerald (which was owned by Elise who then gave it to Sonic when she was captured. Sonic then gave it to Eggman so as to ensure Elise's release. Eggman then put the emerald into his Egg Genesis which Silver and Blaze defeated and obtained the emerald themselves. Silver then gave it to younger Elise in the past as a good luck charm, which showed how Elise came to possess it in the present), the yellow emerald (which Mephiles went after at the end of Shadow's storyline and used to battle Shadow in conjunction with the green emerald), the white emerald (which the Duke of Soleanna sealed Iblis inside Elise's body with. The duke then gave the Emerald to Silver right before he died which Silver used to go back to the future so as to seal Iblis. Blaze then used it and the cyan Emerald to seal Iblis away into a different dimension), the cyan emerald (which Sonic and Shadow obtained from defeating Iblis so as to go back to the future. Sonic then gave the Emerald to Silver, which Blaze used in the future along with the white emerald to seal Iblis away) and the purple emerald (which Mephiles was shown to have the entire way through the series). The red emerald meanwhile was never seen in the main story lines until the Last Story, although it is possible that it is the one Dr. Eggman located when he searched for the Chaos Emeralds on his ship.

Mephiles also somehow uses some sort of "shortcut" when he uses the purple Emerald in his possession to warp all six of the other Emeralds to his location, possibly using the magnetic properties of the Emeralds, and uses their full power to begin his and Iblis' transformation into Solaris. Sonic's friends then have to search through the world's end for each of the Chaos Emeralds: Tails: Yellow, Omega: Green, Knuckles: Cyan, Silver: White, Rouge: Purple, Amy: Blue, Shadow: Red. Lastly, Elise, sharing the hopes and desires of the remaining cast (possibly even including Eggman) to bring Sonic back to the land of the living, uses all seven Chaos Emeralds to bring Sonic back to life, in the form of Super Sonic, who thanks Elise and shares his power with fellow hedgehogs Shadow and Silver.

Sonic Riders
In Sonic Riders, the first one to be seen was stolen by the Babylon Rogues but it is unknown which one it was. After that, the only time they are featured was as the entry fee for the World Grand Prix and when Jet 'won' the race and used the emeralds to power the Key to Babylon Garden as Dr. Eggman instructed to raise the Babylon Garden from Sand Ruins.

Sonic Rush Adventure
In Sonic Rush Adventure it is suggested by Blaze that the Chaos Emeralds have a mind of their own. They appear in her dimension for no indicated reason and one must race Johnny for the Chaos Emeralds, although it is possible that Sonic had them with him before he arrived in the Sol Dimension and they scattered during the transition (note that the Chaos Emeralds in the Sol Dimension would likely have the same effect as the Sol Emeralds in the Chaos Dimension as shown in Sonic Rush).

Sonic Chronicles: The Dark Brotherhood
In Sonic Chronicles: The Dark Brotherhood, the emeralds are stolen one-by-one by the lost clan of echidnas known as the Nocturnus Clan (who are often referred to as the "Marauders") in order to use their magnetic relationship with the Master Emerald to attract the Master Emerald and Angel Island itself to their base of operations. The Chaos Emeralds later are taken by Ix into the Twilight Cage, and distributed amongst the Kron (to power their factory), the Zoah (as a power-source for a secret weapon to use against the N'rrgal), the N'rrgal (as a weapon against the Zoah), the Voxai Overmind, and Ix's two Gizoid prefects, Scylla and Charyb. At the end of the game, the emeralds are all brought back together and Sonic uses them to become Super Sonic and battle a Master Emerald-empowered Ix. This also includes the Great Emeralds, which are emeralds that have been charged up with Voxai power.

Sonic Unleashed
In Sonic Unleashed, after being caught by an early design of Eggman's "Egg Dragoon", Sonic summons the power of the Chaos Emeralds and becomes Super Sonic to destroy Eggman's fortress. However, Eggman traps Super Sonic in his Chaos Energy Cannon which removes the emeralds from him, reversing his super transformation and drains the emeralds of all of their power in order to power his laser, designed to awaken and release Dark Gaia from the planet. From there, the emeralds are left completely black and powerless, and are taken by Sonic and Light Gaia to the seven sacred shrines on different parts of the planet.

The Emeralds' powers are restored one-by-one, and the seven continents are put back into place as each emerald is restored. At the end of the game, while inside each of the shrines, Light Gaia asks the Chaos Emeralds to bring the shrines to him, and the emeralds, as well as the shrines, appear inside the core of the planet, with the shrines combining together to build the Gaia Colossus, which Light Gaia controls via his own power. The Chaos Emeralds are lastly used by Sonic to become Super Sonic.

Sonic Colors
In the Wii version of Sonic Colors, the Chaos Emeralds only appear in the Sonic Simulator. To collect the Chaos Emeralds the player must unlock and finish all the Sonic Simulator levels which requires gathering all 180 red rings from the levels. Once done, the option to use Super Sonic must be activated from the options menu. Sonic cannot use Wisps in this mode (an alternate route appears in areas that absolutely need Wisps), and requires fifty rings to transform, but he gains bonus points every few seconds it's active and has infinite boost power, Super Sonic retains most of his old mannerisms in games like Sonic the Hedgehog 2 such as gliding when picking up speed (and the fact Sonic needs fifty rings to transform once more as usual). In the DS version of Sonic Colors, Chaos Emeralds are once again collected through Special Stages. After all of them are obtained, Super Sonic is playable only to beat a secret, optional boss called Nega-Mother Wisp.

Sonic Generations
In the Xbox 360/PS3/PC versions of Sonic Generations, both Sonics must collect the Chaos Emeralds before the battle against the Time Eater. Classic Sonic gets the Purple and Green Emeralds and Modern Sonic gets the Yellow, Blue, White, Red and Cyan Emeralds.

For some unexplained reason (possibly due to the Time Eater's actions) the Emeralds end up in the White Space. There, the Purple Emerald is found by Classic Metal Sonic, the Yellow Emerald is found by Shadow, and the White Emerald is found by Silver. The remaining Emeralds - Green, Blue, Red, and Cyan - end up getting drained of their color and drift through though the White Space, and the Sonics have to restore them by fixing the worlds. After Modern Sonic defeats the second boss, Perfect Chaos, the Time Eater appears but is repelled by the now-colorless red Chaos Emerald. After the Sonics restore Planet Wisp, the red Chaos Emerald regains its color and Modern Sonic catches it by perform a Sonic Boost in mid-air, much to the amazement of Classic Sonic.

In order to gain access to the Center of Time, Modern and Classic Sonic have to place all the Chaos Emeralds into the broken gears near the entrance in order to open it. During the final confrontation when both Sonics get badly injured by the Time Eater, Sonic's friends appear and cheer on both Sonics. The Chaos Emeralds then emerge from the Sonics, reacting to their friends' encouragements and they transform both of them into Super Sonic.

In the 3DS version, Modern Sonic gets the Chaos Emeralds through Special Stages.

Sonic the Hedgehog 4
Beginning with Episode I, collecting the emeralds works the same way as it did in the original Sonic the Hedgehog game, by collecting 50 rings and entering the Special Stage at the end of an act. Sonic would then need to navigate through a series of mazes that constantly tilt clockwise and counterclockwise, with many obstacles to reach the emerald. In Episode II, the emeralds are obtained by reaching the end of an act (with the exception of boss acts and the first acts of Sky Fortress Zone and the Death Egg mk.II Zone) with 50 rings and jumping into the giant ring past the sign post, and completing Special Stages designed in a half-pipe, which pays homage to Sonic the Hedgehog 2.

Other Game Appearances
All seven Chaos Emeralds can also be seen in Super Smash Bros. Brawl when Sonic transforms into Super Sonic and when he turns back to normal. The Chaos Emeralds can also be seen on Super Sonic's trophy. In one of Sonic victory poses Sonic is seen holding a blue Chaos Emerald.

In Mario &amp; Sonic at the Olympic Winter Games, the Chaos Emeralds appear in the Dream Figure Skating (Sonic) event. The players team must recover the Emeralds from Flappers and then use them to defeat a frozen version of the monster, Perfect Chaos.

In Sonic & Sega All-Stars Racing, The Chaos Emeralds are seen when Sonic transforms into Super Sonic and Shadow transforms into Super Shadow. Also the Item logo for these All-Stars moves has a picture of all seven Chaos Emeralds.

Artifical Emeralds
It is possible to create synthetic Chaos Emeralds with the same wavelength and properties as the originals, but with less power. This has been proven by Tails in Sonic Adventure 2 and by both Tails and the Metarex in Sonic X. However, the Metarex-made Emeralds seem to phase out after use, becoming fragile and useless; even without using them these Emeralds are fragile themselves as they can be hand-crushed easily as shown by Shadow and Rouge.

The Metarex-made Emeralds seem to only have negative energy inside them as Sonic became Dark Sonic when he used a hoard of their fake Chaos Emeralds. It is mentioned that the Metarex made artificial Chaos Emeralds to trick Sonic and the others from getting their hands on a real Emerald in episode 57.

In addition, the artificial emeralds can also be used to sabotage devices that require Chaos Emeralds to power them. It was because of this that Tails attempted to place a fake Chaos Emerald into the Eclipse Cannon console and render it inoperable. In addition, because it had the same wavelength and properties as the originals, artificial emeralds also allowed the user to access Chaos powers just as a genuine Chaos Emerald would, which is especially apparent with how Sonic escaped from near-certain death at the hands of Eggman and how Shadow teleported back to the Blue Typhoon after being launched far away by the Sonic Driver/Power Cannon in episode 73 of Sonic X.

Sol Emeralds
The Sol Emeralds are the equivalent jewels from Blaze the Cat's dimension, appearing in Sonic Rush and Sonic Rush Adventure.

Guardians
The Chaos Emeralds were originally guarded by Chaos, a Chao that had mutated due to contact with the Chaos Emeralds, and that protected both the Emerald Shrine and the other Chao that lived there. Knuckles guards them as well as the Master Emerald.

Tikal found Chaos and the Chao in her ancient Echidna family. She loved them and cared for them, but her father found out about them and wanted the power of the Emeralds for himself. He attacked the Emerald Shrine and tried to steal the gems, but Chaos absorbed the power of the Emeralds, became Perfect Chaos and destroyed the Echidnas. Tikal appealed to the Master Emerald to seal Chaos away inside it, sealing her own spirit in the process. The Chao lived on and bred, however.

This is the point at which the Echidnas took over in protecting the Emeralds. Knuckles is the Echidna that protects them in the time of the current Sonic the Hedgehog timeline, and also the only Echidna left according to the Sonic the Hedgehog 3 manual (in the Sonic Team storyline, other continuities like the American Sonic comics have more echidnas in existence).

Angel Island was not afloat in the time of Tikal, but was instead located in the ocean near the Echidna city (now Mystic Ruins). It's possible the Floating Island was created when Perfect Chaos arose before Tikal sealed him which there is evidence of in the Sonic the Hedgehog 3 manual. If this is true, the reason it does float high in the sky is most likely in order to protect the Emerald from invaders who might try to steal it (like Dr. Eggman eventually did).

Another reason for the fact that the Angel island floats, could be that the Master Emerald's energy causes the island to rises high above the surface. During the time of Tikal's life the Chaos Emeralds canceled out the Master Emeralds effects and after Chaos used the Emeralds to become Perfect Chaos, the lifting effect of the Master Emerald started (although it is not shown in Sonic Adventure). This is extremely likely, given that Sonic needed to retrieve the Master Emerald so the island could rise and that the island began to sink and wobble in the sky after the Master Emerald was stolen again by an Eggrobo in Sonic & Knuckles.

Strangely, when the Chaos Emeralds become Super Emeralds in Sonic 3 & Knuckles, which happens during the story of Sonic the Hedgehog 3 and Sonic & Knuckles, the island still floats in the air. The question is, why does it float if the Super Emeralds are in the same chamber as the Master Emerald? This may be true because the Master Emerald can cancel the Chaos Emeralds, or enhance them to make Super Emeralds. This may mean that the Master Emerald provides power for the Chaos Emeralds, and can be made to stop their power or maximize their power in close range.

In the Archie Comics storyline, Knuckles is merely the latest in a long line of Master Emerald protectors, known as the Brotherhood of Guardians.

Blaze the Cat is the Guardian of the previously mentioned Sol Emeralds.

Number
In the first game of the series, Sonic the Hedgehog, there were six Chaos Emeralds. This was also true for the Game Gear/Master System games Sonic the Hedgehog and Sonic the Hedgehog 2. The number was extended to seven Emeralds in Sonic the Hedgehog 2 for the Mega Drive, and that number has been consistent ever since, with a few exceptions such as most other 8-bit titles.

In the arcade game Sonic the Fighters, in order to travel to the Death Egg II, the player must collect all the Chaos Emeralds. Each character held an Emerald in the "story mode", and to get another one from a different character, they must be defeated in a fight. However, instead of the traditional seven Emeralds, there are eight. The widely accepted reason for this is because there are eight fighters, and so Sega added another Chaos Emerald. Some fans believe that this eighth Emerald is fake, but it is usually treated as a gameplay device rather than a significant plot element. There is also the possibility that the eighth Emerald is in fact the Master Emerald because it was obtained by Knuckles. Though the Master Emerald is green, and Knuckles' Emerald was red, there is the possibility that the Master Emerald can influence the color of the Emeralds (including itself) in addition to the amount of power they will release. This would explain why the Emeralds occasionally appear pink or orange. Incidentally, the color of the Master Emerald can be manipulated due to a glitch in Sonic & Knuckles. Note that early Japanese manuals identified the Master Emerald as an eighth, larger Chaos Emerald. However, the term usually applies to the seven smaller Emeralds.

In Sonic the Hedgehog 3, after accessing the Sound Test and entering a code, the player has access to a secret, and very difficult, 8th special stage. Upon completion, this stage yields the gray Emerald. In Sonic 3 & Knuckles, after accessing the Sound Test, two unused Special Stages could be accessed (one Chaos Emerald stage, with the same layout as the one in Sonic the Hedgehog 3, but with different colored panels, and one Super Emerald Stage). They unlocked a "golden" Emerald (instead of the gray one as in Sonic the Hedgehog 3). After that, the player goes on to the Angel Island Zone stage. This Emerald is considered a glitch.

In Sonic the Hedgehog Spinball, there appeared to be 16 Emeralds, all of which were dark blue. Sonic may have been collecting the same Emeralds each stage, however.

Colors
In the original Sonic the Hedgehog, the six Emeralds were blue, yellow, pink, green, red and silver. A seventh, purple Emerald then appeared in Sonic the Hedgehog 2. In Sonic the Hedgehog 3, the pink Emerald was replaced with cyan one, and the yellow Emerald became orange. In Sonic the Fighters, there were eight emeralds, one for each playable character: Sonic (blue), Tails (orange), Knuckles (red), Amy (pink), Bean (green), Bark (yellow), Fang (darker purple), and Espio (violet). The orange emerald was colored yellow again in Sonic Adventure, and the colors of the Emeralds have remained constant ever since, as (in Sonic Advance/Sonic Rush order) red, blue, yellow, green, white, cyan, and purple. The white Emerald often appears gray, and Sonic R had both a yellow and an orange Emerald instead of a blue/cyan one (the Chaos Emerald was blue in the racing course it was found in, but the screen after the race shows it as cyan). In Sonic X, the Emerald colors were: Dark Blue, Cyan, Yellow, Purple, Red, White and Green.

(Early releases of the Jazwares Super Pack with the Super States of the three hedgehogs (Sonic, Shadow, and Silver) and the seven Chaos Emeralds had the orange emerald instead of the cyan emerald. The orange emerald was replaced with the light blue/cyan emerald in newer packs.)

Certain games have used their own unique colors for the emeralds - in the 8-bit version of Sonic the Hedgehog they are light blue, dark blue in Sonic Spinball, while in Sonic Battle they are all green. In the Sonic the Hedgehog comic series by Archie Comics, green is the color of most Chaos Emeralds. Special zones sometimes house Emeralds that are white (see Super Sonic vs. Hyper Knuckles, February 1996), a black Emerald served as a prison for Chaos 0 (see Sonic the Hedgehog #80) and mention is made of a red Emerald on an alien home world (see Sonic the Hedgehog #126). In the UK's Sonic the Comic series, the emeralds are blue, yellow, red, green, orange, grey and purple. In Sonic Heroes, Team Dark's Special Attack involved stopping time with Chaos Control, even if you have not collected any emeralds. This is apparently a fake emerald, and it looks slightly like tinted glass (even though when looking at the texture files of the game, the texture for this Emerald is the same as in Sonic Adventure 2).

Sonic the Hedgehog Story Comic
Chaos Emerald is mentioned in Sonic the Hedgehog Story Comic Volume 1. According to the doctor Eggman, Chaos Emerald contains unfathomable energy and nobody has ever been able to find one before. With one of it, he'll be able to boil world's largest egg in the world's largest pot, which has been dreaming since as a child. One of Eggman's robots detects a Chaos Emerald from north west of South Island, in Green Hill Zone. Chaos Emerald is never mentioned in later volumes.

Sonic the Comic
In the UK's Sonic the Comic, the history of the Emeralds is expanded considerably, though some points contradict the storyline of the games.

The Chaos Emeralds were originally green Raw Emeralds from the Sacred Emerald Mine of the ancient Echidnas, but were infused with Chaos Energy by the Drakon Empire in the distant past. When brought together outside of certain stabilizing conditions (e.g. extreme cold), the Chaos Emeralds generate a chain reaction of Chaos Energy and warp to the Special Zone.

Six of the Chaos Emeralds were brought to Mobius in the distant past, and subsequently used by Doctor Ovi Kintobor in an attempt to rid Mobius of evil with his Retro-Orbital Chaos Compressor (ROCC). An accident involving the Emeralds and the ROCC transformed Kintobor into Doctor Ivo Robotnik.

The Emeralds were gathered by Sonic and protected from Robotnik, but were eventually returned to the Floating Island and placed in the care of Knuckles, the appointed Guardian of the Chaos Emeralds.

Archie Comics

 * Main Article: Chaos Emeralds (Archie).

In the Archie Comics' Sonic the Hedgehog and its spin-offs, the Chaos Emeralds are much more numerous than they are in other continuities; in reality, there are far more than just seven. They are also connected to the "Power Rings", which are produced by harnessing the energy of the emeralds. This continuity explains a more scientific origin than a conventional mystical one found in other Sonic continuities. It was revealed in a recent storyline that the Emeralds were the product of the Xorda (the aliens that transformed Earth into Mobius) gene bombs. Specifically, they were formed by the absorption of the Xorda gene bombs' massive energy release into underground beryl deposits.

In addition, there is the existence of rare 'Super Emeralds'. The origins of these can also be attributed to the Xorda-induced cataclysm albeit these Emeralds are the product of much more concentrated energy absorbed into the beryl material. What's more, there's another level of existence known as "the Chaos Force", which is tied to the Chaos Emeralds and has been tapped into by the "Guardians of the Floating Island", Knuckles' ancestors - one theory is that the Xorda gene bombs allowed the energies of the Chaos Force to spill out into this plane and take the form of Chaos Emeralds or more canonically, the Chaos Force was only recently discovered and its existence made aware to the inhabitants of Earth/Mobius. There is also a special Black Chaos Emerald that served as the containment vessel for Chaos and Tikal. Mammoth Mogul's own Chaos Emerald was used in a similar manner to temporarily imprison him.

While on an alien world, Sonic discovered a batch of red colored emeralds (officially designated outside of the storyline by the editor as "Chaos Rubies"), which rather than transform him into Super Sonic, created a mad, power-crazed Super Sonic that was independent of Sonic's body (similar to Fleetway's normal Super Sonic). No such explanation has been offered as to the origins of these particular types of Emeralds, though the catalyst for their existence can be alluded to a possible previous altercation with the Xorda or perhaps the idea that certain cataclysms of immense energy combined with certain minerals can follow the same suite as Earth/Mobius' Chaos Emeralds.

It was revealed by A.D.A.M. that there were many Chaos Emeralds scattered across the universe, in his plot to use Shadow and Tails to retrieve them. A.D.A.M. later succeeds in collecting all the Chaos Emeralds of the universe. While Sonic transforms into Super Sonic as a distraction, Super Shadow and Turbo Tails send all the Chaos Emeralds to the Zone of Silence. There, the Zone's new ruler, Feist fused all of them into the seven differently colored jewels seen in the games. It is shown that each emerald has a power that differs it from the others, the grey emerald can heal people from sickness, the purple emerald can restore the insane, and the cyan emerald can alter reality.

Adventures of Sonic the Hedgehog
The Chaos Emeralds made an appearance in DiC's cartoon series Adventures of Sonic the Hedgehog in a four-part story called "Quest for the Chaos Emeralds", but they are very different from the game versions. There are only four, and instead of different colors they are all different shapes. The Emeralds are hidden in time instead of a certain place. Each Emerald focuses on a different power:
 * Invisibility: This made the holder invisible, and at first seems to be invisible itself. However, the invisibility can be negated if the holder is covered in substances such as sand or flour. Buried on an island in the time of pirates.
 * Invincibility: This granted invincibility, but it is more complicated than simply holding it. To trigger its powers permanently, its first holder must become king. As its title suggests, the holder becomes completely immune to physical harm, as well as becoming quite muscular and gaining superhuman strength. Interestingly enough, Tails is able to access its power despite not being king, (Possibly due to Robotnik already activating it when he became king.) Guarded by Merlynx the Magician in the Middle Ages.
 * Immortality: This granted immortality to the holder. This is not simply an inability to die of old age or natural causes; any injuries that the holder suffers immediately heal within seconds to minutes; in a way, this eliminates the need for the Emerald of Invincibility. Resided with Robotnikhotep, Robotnik's mummified ancestor, in Ancient Mobigypt.
 * The Power of Life: The most powerful of the four, this emerald can give or take life from anyone and anything, even if they're already dead. This was hidden on an island, guarded by a volcano entity who would only yield the emerald after a sacrifice was offered.

Robotnik forced a scientist, Professor Caninestein, to build him a time machine to grab the Emeralds and become the Supreme High Robotnik. In this form, he could rule the universe. Unfortunately for him, the scientist granted Sonic and Tails the duty of making sure he does not get them. Assisted by Caninestein's various time-travel devices (sneakers, surfboard, skateboard) and the locals from each time area (some were parodies of real historical figures or even Sonic's own ancestors) Sonic and Tails foiled Robotnik's first attempts at the first three Emeralds, facing many life-threatening situations on the way.

But Robotnik tried again and succeeded, using all four emeralds to transform into a form he dubbed "Supreme High Robotnik". Supreme High Robotnik almost killed the duo by sending them into the Big Bang (represented by a giant stick of dynamite which would bring the universe forth once it explodes), but they managed to escape, and Sonic formed an idea. Completely ignoring the rules of paradox, the duo managed to gather their past selves (who, as keen-eyed viewers will notice, are all shown using the skateboard instead of the devices they used previously) after they left each time area. Five Sonics and five Tails went back to the present time where Supreme High Robotnik was still wreaking havoc. The team that now consisted of ten all worked together to steal back the Emeralds and return them to their original places.

The AoStH episode "Fast and Easy" featured a fifth Chaos Emerald which is supposedly the most powerful - it does not focus on a specific attribute, so it is more like the game version. This Emerald is of a brilliant cut and, unlike the other Chaos Emeralds, is fashioned into a ring. Its power is apparently dormant until it is plugged into a pedestal in the "Secret Zone", and then it is seemingly capable of doing anything. Robotnik intended to use this power to terrorize the world with floods, but his plans were thwarted when a thief called Easy Eddie stole it from him. After Sonic had realized what exactly was going on and the magnitude of the problem, the ring was pried from Eddie's finger. However, the thief stole it again and bargained with Robotnik, but it was a trick and Robotnik gained the ring. But as always, Sonic messes up Robotnik's plans by stealing the ring from the pedestal, and subsequently throwing it into the sea. As for Easy Eddie, he managed to escape from Robotnik and gave up being a thief.

Sonic Underground
Another of DiC's Sonic adaptations had Chaos Emeralds in it, but very little is known about them. Like in the games, they are a source of incredible power but the exact number of them in existence in unknown. Knuckles guards one Emerald on the Floating Island, and Robotnik tried to steal it and frame Sonic for it. It failed in a way very similar to the Archie story of the same basic idea.

In a three part episode towards the end of the series' run, Dr. Robotnik managed to acquire another Chaos Emerald and used it to power his enormous indestructible fortress, the Fortress of Altitude (otherwise known as Egg Fortress). However, he lost the Emerald to his lackeys Sleet and Dingo, who stole it after deciding to leave Robotnik and get their own power. When Dingo attempted to go solo, the Emerald broke, and threatened to destroy Mobius with waves of Chaos.

Forced to work together with Robotnik, Knuckles and the royal siblings located the fragmented Emerald. However, when Sleet attempted to contain it by placing it within Dingo - transformed into a safe - it reacted with Dingo's mutation abilities. Becoming a giant, shape-shifting monster, Dingo threatened to destroy all of Mobius before he was brought down. The shattered Emerald was then placed within a special canister by Knuckles and taken to the Floating Island.

In the episode Mobodoon, it is possible that the crystal seen generating Mobodoon's beauty (later stolen by Robotnik) is in fact a Chaos Emerald, as it looks very similar to one, and at one point Manic uses the crystal to recharge his siblings' medallions.

Sonic X
In Sonic X, the Chaos Emeralds echoed their role in the games as objects that were sought after by all parties. However, the series also introduced a new concept: Chaos Emeralds reacting to each other. Whenever Chaos Emeralds are brought together without being given time to adapt to each other's presence, they release immense quantities of energy. (This concept however disappeared after the first half of Series 1, as in the second half and Series 2, the Chaos Emeralds are brought together with no ill effects) Also, all seven being in one place results in them releasing energy that push them away from each-other. This is likely the anime's way of creating an explanation as to why the Chaos Emeralds end up scattering, as opposed to when in the video games they just seem to mysteriously scatter for no reason. While that's generally why they scatter in Sonic X, at the start of the second series Sonic actually did have seven emeralds, and he scattered them across the galaxy to keep Dark Oak from taking them from him (Dark Oak was too powerful for Sonic to defeat even when he was in his Super Form). Later in the same season, the Emeralds are scattered again by a gravity warp created during a battle between Super Sonic and Super Shadow. In the Season 2 episode A Robot Rebels, Knuckles has a vision of the past showing Tikal at the Emerald Shrine. The 7 Chaos Emeralds are there, but quite different than the modern ones. They appear much larger, are shaped differently.

Emerald Shards
Emerald Shards are fragments of Chaos Emeralds crushed by Doctor Eggman found in Sonic Battle. They are used to operate the E-121 Phi model robots. Once an E-121 Phi is destroyed they drop their Emerald Shard and either break down or retreat. When 5 Emerald Shards of the same color are united, a Chaos Emerald can be created. Tails is the one who first discovered how Emerald Shards work and characters often visit him to have their Chaos Emerald reassembled which Emerl would soon absorb. E-102 Gamma is also seen with an Emerald Shard which he absorbs to injure Shadow.

Trivia

 * The Chaos Emeralds are not indestructible as shown in Sonic Underground, Archie, and Sonic Battle; the Emeralds have been seen breaking but are easily repaired.
 * Just one Emerald supplies a lot of power. In Sonic X, when Sonic was fighting E-18 Guerra-Hard, Sonic obtained two Emeralds and was granted the power of invincibility as well as flight, despite not having the other Emeralds. Similarly, Mephiles managed to gain the power of turning the battlefield into darkness with just one Chaos Emerald, and managed to create a massive army of clones just by using two Emeralds in Sonic the Hedgehog 2006. One emerald alone contains enough power to knock back and repel the Time Eater.
 * However, all seven Emeralds are needed for Sonic to turn into Super Sonic, but the same powers as Super Sonic (invincibility and flight, excluding Chaos powers, i.e. Chaos Control) are given for two emeralds, as shown in Sonic X.
 * In the Archie comics, a single Chaos Emerald alone has shown the power to create an entire Zone (universe), wheres in the games, it's highly likely that it would require at the very least three Chaos Emeralds to perform such a feat, since Darkspine Sonic has recreated the universe of the Arabian Nights with only three of the seven World Rings, which are believed to be the Arabian versions of the Chaos Emeralds, however the emeralds themselves are possibly superior due to being sentinent.
 * The Emeralds can be enhanced in more ways than one. As shown in Sonic Chronicles: The Dark Brotherhood, the Overmind somehow transformed two Chaos Emeralds into Great Emeralds. Finally, in Sonic 3 & Knuckles the Chaos Emeralds can be enhanced to Super Emeralds.
 * It is occasionally implied that the Chaos Emeralds (much like the Master Emerald) are sentient. As stated at the end of Sonic Rush Adventure, Tails believes that the Emeralds wanted to be used to build the SS Tornado EX. It was also theorized by Blaze that the Chaos and Sol Emeralds brought Sonic and Tails to her world for a reason. And in Sonic Rush, Eggman and Eggman Nega state that in close proximity, the two sets of Emeralds call out to each other.
 * In Sonic Adventure, the Emeralds are said to be able to turn thoughts into power, but in Sonic the Hedgehog (1991), Sonic seemed surprised when new plant life emerged. It is, however, possible that Sonic didn't know what they were, and simply wished they would do something for the benefit of South Island, and they granted it.
 * When the colors of the Chaos Emeralds are inverted, they simply swap colors, giving the appearance that the position of the Emeralds simply changed.
 * When causing a super transformation, the Emeralds usually surrounds the users in a circle and starts rotating around the users, before being absorbed.
 * In an unused Sonic Colors beta voice clip, Dr. Eggman stated that Chaos Emeralds are less powerful than Hyper-go-on.
 * However, this may not be the case as Super Sonic was able to defeat the Nega-Mother Wisp, the final boss of the DS version.
 * In Sonic 2, it is possible to collect all seven within Emerald Hill Zone, provided the player is careful with the order in which Star Posts are activated (and very skilled at the Special Stages).
 * The gemstone-appropriate names for colored beryls are scarlet emerald (red), golden beryl (yellow), emerald (green), aquamarine (cyan), blue goshenite (blue), morganite (purple), and goshenite (white).
 * The Chaos Emeralds' power has been drained twice. The first time by Perfect Chaos in Sonic Adventure, and the second time by Dr. Eggman's trap in Sonic Unleashed.
 * Starting with Sonic R, the Chaos Emeralds themselves took on a brilliant diamond cut which has been game canon ever since.
 * The Chaos Emeralds that appear in the Tikal visions in Sonic Adventure are much larger than the Chaos Emeralds that appear elsewhere in the game. In fact, their size and proximity to the Master Emerald may indicate that they are in fact Super Emeralds.
 * Aside from the green one, these are not technically the real world gem known as emeralds, due to the fact real world emeralds are green.
 * The Rainbow Gems from a game Sega made "Castle of Illusion" starring Micky Mouse bear a strong resemblance to the Chaos Emeralds going as far to reuse Chaos Emerald Models for them in the Remake.

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