Master Emerald (Sonic X)

The Master Emerald (マスターエメラルド) is an object that appears in the anime series Sonic X and its comic series published by Archie Comics. It is a massive, green emerald and a mystical relic of immeasurable power from Sonic's world The one who controls the Master Emerald can nullify and control the Chaos Emeralds, making the Master Emerald a very valuable gem.

The Master Emerald's eternal resting place is on Angel Island where its power the island afloat in the sky; without it, the island will fall down. For generations, the Knuckles Clan has guarded the Master Emerald, the mission being inherited from one generation to the next. In the present day, the role has been passed onto its last surviving member, Knuckles the Echidna.

When Knuckles was sent to Earth, the Master Emerald was left unprotected until it came to Earth as well. During its time on Earth, the Master Emerald became a key factor in several battles until it was returned to its dimension. It would later be used as a vital power source for Knuckles and his allies' battles against the Metarex.

Ancient times
The Master Emerald's true origins are shrouded in mystery. The earliest documentations of it date back to the era when Knuckles Clan still thrived. In those times, the Master Emerald and the Chaos Emeralds resided in a sacred shrine in the Mystic Ruins where a colony of Chao lived peacefully, guarded by the mystical water beast Chaos. Eventually though, Pachacamac, leader of the Knuckles' Clan, set his greedy eyes on the Master Emerald and the Chaos Emeralds to gain ultimate power for his clan. Learning of her father's plans to raid the shrine, Tikal failed to make the shrine's residents leave. Instead, the residential Chao let her see the Master Emerald. As if the Master Emerald spoke to her, Tikal recalled an old mantra telling of the controller of the Chaos Emerald and it made her understand how it was that controller.

When the time of the raid came, Pachacamac and his warriors brought destruction to the Emeralds' shrine. Tikal attempted to stop her clan, but her pleas fell on deaf ears. Trampling over Tikal and the Chao alike, the Master Emerald and the Chaos Emeralds were left for the echidnas' taking until Chaos blocked their path. In a fit of rage, Chaos took the Chaos Emeralds' power and wiped out most of Tikal's tribe. With Chaos lost to rage, Tikal prayed to the Master Emerald with her mantra to stop Chaos, which the gem responded to by sealing Chaos inside itself along with Tikal so Tikal could sooth its anger. After that, the survivors from the Knuckles Clan would devote themselves to protecting the prized gem on Angel Island. In the present day, this task has been inherited by Knuckles the Echidna, the last of the Knuckles Clan.

Chaos Emerald Saga
The Master Emerald was eventually left unprotected when Knuckles got sent to Earth by Chaos Control. During most of his time there, Knuckles was on an almost obsessive quest to get home to protect the Master Emerald. While no harm was done in Knuckles' absence, Angel Island and the Master Emerald were transported to Earth by a giant Chaos Control triggered by Super Sonic and the E-99 Eggsterminator.

Chaos Saga
Following the Master Emerald's arrival on Earth, Knuckles resumed his duty to protect it. Six months later though, the Master Emerald was shattered by Dr. Eggman to release Chaos, its pieces being scattered far and wide and causing Angel Island to fall into the sea. As such, Knuckles began searching for the fragments across various areas. Whenever Knuckles found a fragment, it would show him a vision of Tikal and Chaos' past. After Knuckles had brought most of its pieces together, the partially restored Master Emerald showed Knuckles that the remaining fragments were on the Egg Carrier. Not long after, Knuckles brought the final pieces back and fully restored the Master Emerald. When Chaos had finally been calmed down by Sonic, Tikal and Chaos returned to the Master Emerald to live in peace.

Shadow Saga
Shortly after Perfect Chaos' attack on Station Square, the Master Emerald was stolen by Rouge the Bat despite Knuckles' attempt to stop her and taken to Space Colony ARK. However, Knuckles followed her up to the ARK where Rouge let him take it back after he saved her life. When the Space Conoly ARK was sent on a crash course into earth which would destroy the planet, Rouge had the idea of using the Master Emerald to deactivate the Chaos Emeralds that were current powering the ARK's descend. With help from Sonic, Decoe, Bocoe and Shadow, the Master Emerald was brought to the ARK's core where Knuckles called upon its power and shut down the Chaos Emerald.

Homebound Saga
When it came to light that the presence from everything from Sonic's world were threatening to freeze time, the Master Emerald and all else not native to Earth were sent back to their world using a machine Tails and Chuck Thorndyke had created.

Metarex Saga
Following the return home, the Master Emerald was peacefully protected by Knuckles on Angel Island over the next six months. At that point, the Master Emerald served as the power source for Christopher Thorndyke's crossover into Sonic's world. As a result of the time difference between Earth and Sonic's world, Chris physically regressed six years which were stored inside the Master Emerald, at least according to Eggman's theory.

As Sonic and co. prepared to set out to travel around the galaxy and battle the Metarex, an alien race of cyborgs bend on universal dominance, the crew took the Master Emerald from Knuckles to use it as a power source for the Blue Typhoon, a massive spacefaring vessel, which Knuckles was forced to accept. Onboard the Blue Typhoon, Knuckles would call upon the Master Emerald's power in time of need, most importantly to power the Sonic Power Cannon, the ship's most powerful weapon. In the final battle against Dark Oak, the Metarex's leader, the crew attempted to use the Master Emerald's energy to destroy Dark Oak with an extremely powerful shot from the Sonic Power Cannon. However, this attempt came at a terrible cost for Knuckles: the attack pushed the Master Emerald beyond its limit, leaving it shattered and powerless.

After defeating the Metarex, Knuckles returned the Master Emerald's shards to Angel Island where he could watch over them until it power could be restored naturally, though the process would take some time. The Master Emerald's destruction also meant Chris' age data was corrupted, preventing him from returning home through that method.

Powers and traits
The Master Emerald is an all-powerful gem on par with the Chaos Emeralds, and holds unbound and infinite amounts of chaos energy. As its primary function, the Master Emerald has the power to fully control everything that the Chaos Emeralds do, which grants it the ability to completely negate the Chaos Emeralds' power. The Master Emerald's energies can as well be harnessed to power machinery.

The Master Emerald appears to have some degree of sentient, as demonstrated when it interacts with Knuckles and Tikal, and can create three-dimensional holographic images within itself as a form of communication. In addition, if the Master Emerald is broken into several pieces, it can repair itself if the shards are brought back together. However, the shattering of the emerald seems to give the shards an explosive trajectory, causing them to fly a great distance which makes the task of gathering them rather painstaking.

Only Knuckles and Tikal are able to talk to, command and control the Master Emerald's power to the fullest. On most occasions, for Knuckles and Tikal to connect to or unlock the power of the Master Emerald, they must recite an ancient quote.