For an unknown length of time, Knuckles the Echidna has been the guardian of the Master Emerald and protected it from anything capable of posing a threat to it. Recently, however, Knuckles was forced to leave his post to command the Resistance against the Eggman Empire during the war, leaving the Master Emerald vulnerable. As a safety measure, the Master Emerald was hidden away on Angel Island. (StH: #2, #3, #8)
The Battle for Angel Island
Eventually, Neo Metal Sonic discovered that the Master Emerald was unguarded. As a result, he launched an invasion of Angel Island. After taking over the island, Neo Metal Sonic fashioned 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. Meanwhile, the Master Emerald called out to Knuckles in distress. (StH: #3, #7, #8)
Eventually, Sonic and Knuckles confronted Neo Metal Sonic inside his fortress in order to secure the Master Emerald. In response, Neo used the Master Emerald to transform into Super Neo Metal Sonic. The Master Emerald was later secured temporarily by Shadow the Hedgehog after he subdued Super Neo Metal Sonic. After Neo Metal Sonic copied Shadow's biodata however, Neo Metal Sonic used it, Sonic's biodata, and the power of the Master Emerald again to transform into Master Overlord. The giant robot incorporated the Master Emerald into itself, which effectively cut Angel Island off from its power, meaning the island was about to fall into the sea. Master Overlord used the Master Emerald to energize and strengthen his transformation. Sonic, Shadow, and Knuckles however, decided to rip the Master Emerald out of the robot to defeat him. To accomplish this, the Resistance fought Master Overlord while Knuckles tried to pound the Master Emerald loose. After an Egg Fleet vessel was flown into Master Overlord, Knuckles managed to tear the Master Emerald free and glide it back to the falling Angel Island where he inserted it into its altar, which restored Angel Island's flight capabilities. After the battle, Knuckles laid on the Master Emerald and rested. With the Master Emerald back where it belonged, Knuckles chose to disband the Resistance in order to free himself from his duties as the organization's commander and devote himself to guarding the Master Emerald like he used to. (StH: #9, #10, #11, #12)
The Master Emerald is a relic of immeasurable power, having been referred to as the most powerful gemstone in the world. It holds unbound power in the form of extremely potent and raw energy which can be harnessed to initiate a Super State, a transformation that grants increased innate talents and other potent powers. Described as the "controller", the Master Emerald also has the special ability to neutralize the Chaos Emeralds, rendering them powerless.
Despite appearing inanimate, the Master Emerald possesses a degree of sentience. This allows it to pull off feats like calling out to its guardian, who shares a special connection to it, when it is in need of help.
For all its powers, the Master Emerald has a few limitations. For example, it cannot neutralize the Sol Emeralds in the same way as it can with the Chaos Emeralds.
- The Master Emerald is based on the object of the same name from the Sonic the Hedgehog video game series.