From Sonic Retro
|“||The seven Chaos are the servers. Chaos is power, enriched by the heart. The controller is the one who unifies the Chaos.||„|
The Master Emerald is a massive, mysterious gem, held on Angel Island and guarded by Knuckles the Echidna. It is possibly the single most powerful object in the Sonic universe, and as such has been embroiled in numerous plots by Doctor Robotnik and other villains seeking to harness the crystal for their own nefarious ends. This powerful gem first appeared in Sonic & Knuckles
The green jewel's principal effect is to control or negate the energies of the Chaos Emeralds (being the "controller" mentioned in Tikal's incantation). But on top of this it is also an artefact of awesome potency in its own right, able to levitate continents, power giant lasers, open dimensional wormholes, and more.
Nothing is known about the origin of the Master Emerald, or the Chaos Emeralds. They have, however, been on Sonic's world for at least the last four thousand years, their earliest known location being a shrine in the Mystic Ruins territory of the ancient Knuckles Clan. After the first Perfect Chaos cataclysm, Angel Island was blasted out of the surface, with the shrine attached. Four thousand years later, the Island and the Emerald is guarded only by the hermetic Knuckles the Echidna.
Role in the Story
The scene originally thought that the green emerald in the Sonic 2 version of HPZ was the Master Emerald, but the interview with Craig Stitt revealed it was supposedly nothing more than a breakable block.
Sonic 3 & Knuckles
|“||Sonic knows that many Emeralds, including the Master Emerald, are hidden somewhere on Floating Island. He bets this Knuckles character knows where they are! Sonic can't let Robotnik get his hands on the Master Emerald. He'd have Death Egg fuel forever — and Floating Island would be destroyed!||„|
— Sonic & Knuckles US manual
The Master Emerald's part in the game includes being stolen by Dr. Eggman, being used to power the Death Egg, fire lasers, allow Mecha Sonic to achieve his Super form, and eventually be restored to Angel Island. If the player collects all of the Super Emeralds, the Master Emerald will begin glowing and grant the player characters their Hyper forms (Super form in Tails' case).
The Master Emerald appeared again in Sonic Adventure for the Sega Dreamcast, where it was again shown keeping Angel Island afloat. The emerald also held within it the ancient monster known as Chaos. In the game, it was shattered by a mysterious force, causing Angel Island to fall, and Chaos and Tikal to escape the jewel's confines. Knuckles spends the game tracking down the scattered shards of the Master Emerald, butting heads with Sonic and unwittingly aiding Eggman in his pursuit of the Chaos Emeralds. All the pieces of the Master Emerald are eventually recovered, though Angel Island cannot rise for long without Chaos sealed inside.
An additional power of the Master Emerald is showcased in the course of the game; A nearly complete Master Emerald shows Knuckles where its remaining shards are (aboard the first Egg Carrier) after Knuckles audiably ponders where they could be. The source of this vision and the Master Emerald's apparent omnipresent knowledge are not revealed.
Sonic Adventure 2
In Sonic Adventure 2, the Master Emerald was again a source of contention as Knuckles fought with Rouge the Bat for possession of it. Dr. Eggman tried to steal it again while they were distracted, but Knuckles voluntarily shattered the Emerald in order to keep it out of his hands. Knuckles and Rouge then set off separately to gather the shards of the emerald for their own reasons. Once all the shards are recollected and the Master Emerald is made whole again, it is used to negate the destructive powers of the Chaos Emeralds in Cannon's Core.
Sonic Advance 3
The Master Emerald is found in Altar Emerald at the end of Sonic Advance 3, and the fight against Altar Emerald's second boss takes place at the base of its shrine. The Master Emerald apparently has the ability to reunite the seven separated pieces of the planet, reversing the effects of Dr. Eggman's worldwide Chaos Control. This is seen at the end of the game's normal ending.
The disappearance of the Master Emerald is the primary reason for Knuckles's involvement in both Sonic Rivals games. In the original, Knuckles' episode reveals that the game takes place almost entirely on Angel Island's future form, renamed Onyx Island in the future. It is also revealed that the Master Emerald is a transcendent object, existing simultaneously in all timelines. Its disappearance from the future caused its disappearance in all timelines.
Sonic Rivals 2
The Master Emerald goes missing once again in Sonic Rivals 2, forcing Knuckles' hand in the story. The situation also causes the team up of Knuckles with Rouge, much to his chagrin. At the end of the game, the heroes find they were in possession of the jewel the entire time. It was sealed within the Chaos Emerald detector they stole from Eggman Nega.
Sonic Chronicles: TDB
Imperator Ix of the Nocturnus Clan echidnas initiates an intricate scheme in order to capture the Master Emerald and use its power to open a wormhole to the Twilight Cage, where his civilization has been imprisoned by Argus. Manipulating the link which the Chaos Emeralds share with their Master, Procurator Shade pulls Angel Island over Eggman's Metropolis, before Ix steals the Emerald from the Shrine, sending the Island plummeting into the city.
Sonic and friends travel into the Cage to recover the Master Emerald from the Nocturne, and manage to bring it back through the portal.
In Sonic Mania, the Master Emerald appears on its altar at the end of Lava Reef Zone Act 2 like in Sonic 3 & Knuckles along with the Super Emeralds which are now cracked and drained of their power. During Knuckles' exclusive boss fight against the Heavy King, leader of the Hard-Boiled Heavies, the Heavy King uses his scepter to absorb the Master Emerald's power and unleash various types of attacks against the echidna.
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 chaos emeralds for himself. He attacked the emeralds and tried to steal them for himself, but Chaos absorbed the power of the Emeralds and became Perfect Chaos, before Tikal appealed to the Master Emerald to seal Chaos away inside it, sealing herself in the process. We know this because Tikal's spirit is of the age when she was sealed, which is the age at which her father attacked the emerald. The Perfect Chaos catastrophy almost totally obliterated the Knuckles Clan, and the backlash from the event hoisted Angel Island into the sky. 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, until the introduction of the Nocturnus, believed himself to be the last of his race.
In other media
In the Archie comics, the Brotherhood of Guardians is a group of echidnas in charge of protecting Angel Island. Knuckles is a descendant from these male echidnas, and is now guardian of the island, doing what his ancestors have done for quite a bit of time. The Archie continuity has the Angel Island echidnas as protectors of a distinct set of Chaos Emeralds, which are amalgamated into the Master Emerald as part of a plan to combat Mammoth Mogul in issue 56.
Sonic the Comic
In Fleetway's Sonic the Comic, the history of the Emeralds is expanded considerably, though some points contradict the storyline of the games. The Grey Emerald is said to be the most powerful of the seven, and has the ability to control the energy of the other Emeralds. However, the Master Emerald can still over-rule its power. The original form of the seven Emeralds were what is now known as the Super Emeralds. They were taken from Angel Island by persons unknown and began to lose their power, reverting to the small emeralds that are familiar to all the Sonic games. Dr. Kintobor planned to use the Emeralds as a storage device to contain all the negative energy in the world, but a freak accident infused him with pure Chaos Energy and turned him into Sonic's lifelong antagonist.
In the Fleetway comics (and contrary to Sonic Adventure), there is no positive energy in the Emeralds; only Chaos Energy. The Emeralds absorb Chaos Energy through contact, draining the victim and growing more unstable. In contrast to this, Sonic absorbs Chaos Energy, which is why he is the only one (storyline-wise) who is able to harness their power and transform into Super Sonic. The only way to stop the transfer of Chaos Energy to and from the Emeralds is to keep them at a cold temperature. In the comic, Super Sonic was an insane, all-powerful version of Sonic created when he absorbs too much Chaos Energy and goes out of control.
It is also implied that it was the Emeralds which created the Special Stages in order to protect themselves from Dr. Robotnik. The comics also claim that the seven original Emeralds were split into fourteen - the emeralds from Sonic 2 and Sonic 3 respectively. These Emeralds were then fused back into seven in the comics. However, this is never proven or implied in the games.
In the IDW comics, the Master Emerald and its background are identical to the game series counterpart. While Knuckles was away from Angel Island, Neo Metal Sonic had discovered that the all-powerful gem was left unguarded, prompting him to invade the island. Once his takeover was complete, Neo Metal Sonic built himself a throne on top of the Master Emerald and a fortress around its shrine. With the gem under his control, Neo Metal Sonic possessed the means of neutralizing Super Sonic in case Sonic tried to use the Chaos Emeralds against him. While this happened, the Master Emerald would call out to Knuckles in distress.
During the Battle for Angel Island, Sonic and Knuckles would confront Neo Metal Sonic, who then harnessed the gem's power and transforms into Super Neo Metal Sonic, putting up a fierce fight for the two heroes. Shadow then showed up and subdued Super Neo Metal; however his presence would allow the robot to copy his biodata and combine it with Sonic's biodata and the Master Emerald's power to transform into Master Overlord. This metal monstrosity incorporated the Master Emerald into himself as his power source, effectively cutting Angel Island off from its power, meaning the island was about to fall into the sea. To take down the metallic beast, the Resistance banded together to distract Master Overlord while Knuckles tried pounding the Master Emerald loose. Tails ramming an Egg Fleet vessel into Master Overlord was just enough for the Master Emerald to be lodged free, defeating him and allowing Knuckles to stop Angel Island from falling. With Neo Metal Sonic defeated and the Emerald back in its altar, Knuckles disbanded the Resistance and resumed his duties as guardian.