Space Colony ARK (スペースコロニー・アーク) was the world's first Bernal sphere space colony (mistranslated to "Bernoulli sphere" in the English translation), built more than fifty years before the events of the Sonic Adventure 2 (its first appearance).
The ARK was used by the government for scientific testing and experimentation, and housed some of the world's finest minds in the most advanced research center of its kind. One such scientist was Professor Gerald Robotnik, grandfather of Doctor Eggman, many of whose inventions remained aboard the ARK until being reactivated many years after his death. It is particularly notable as the "birthplace" of Shadow the Hedgehog.
Gerald's early experiments involved lizards, since they have the ability to regenerate limbs. Gerald's earliest known "prototype of the ultimate life" was the mutant Biolizard, but this creature was deemed too dangerous, and sealed away at the core of the colony.When the government sought to recruit brilliant scientists aboard the ARK, Gerald Robotnik initially rejected their attempts to recruit him. However, he reconsidered when he discovered that his granddaughter Maria Robotnik had a terminal disease known as Neuro-Immuno Deficiency Syndrome (NIDS). Gerald brought Maria with him to the ARK, where he set about not only finding a cure, but also discovering the secret of immortality. To this end, he attempted to create an "Ultimate Lifeform". The workers and scientists aboard the ARK thought this project was impossible, so they began calling it "Project Shadow", because it was an unreachable goal. Gerald liked the name, so it stuck.
Next, he based his creature off of an ancient Echidna prophecy he had discovered on New Earth (a mural in the Hidden Palace on Angel Island showed Super Sonic defeating Gerald's grandson, Eggman). In this time he also made contact with the Black Comet, and enlisted the help of the alien Black Doom, who supplied genetic material to allow Gerald to complete Project Shadow. However, little trusting Black Doom, Gerald secretly began construction of the Eclipse Cannon, a powerful weapon that he built into the colony itself.
While aboard the ARK, Gerald also began experimenting on an ancient robot he had discovered, called the Gizoid (although the robot eventually came to be called Emerl). "Project Gizoid" later destroyed a large chunk of the ARK, after copying some of the super-weapon's abilities.
When the government became skeptical of Gerald's work on immortality, he sent them the dangerous Gizoid, to buy time to finish off Project Shadow. When he still refused to shut down his research, GUN raided the ARK, and discovered that, with some behind-the-scenes help from Black Doom, Project Shadow had already been completed in the form of Shadow the Hedgehog.
Shadow and Maria (who had by then become close friends) tried to escape the intruders, but Maria was shot defending Shadow. With her last breaths, she trapped Shadow in a stasis tube, and made him promise to protect New Earth, the planet she had always watched and wanted to visit, before sending him away with the words, "Sayonara, Shadow the Hedgehog". Her last words were, "Bring hope to humanity".
Since Maria Robotnik was killed during the raid, the news of her death sent her grandfather into despair and insanity. He plotted revenge against the entire planet. He reprogrammed several of his old experiments, including the Eclipse Cannon and the Biolizard, with the intention of devastating planet New Earth. He also programmed Shadow to bring the Chaos Emeralds to the ARK, having presumably recovered Shadow's escape pod before being caught and executed by the government. GUN attempted to shut down all of Gerald's projects, locking up Shadow's stasis tube and sealing away the Biolizard, which had nearly decimated the GUN invaders. Space Colony ARK was forgotten for fifty years.
During Sonic Adventure 2, a reawakened Shadow the Hedgehog led Doctor Eggman and Rouge the Bat to the ARK as part of his own plans to get vengeance for the death of Maria. They planned to activate the Eclipse Cannon, a powerful weapon that, when powered by Chaos Emeralds, could destroy a planet or even a star. When six of the seven emeralds were connected to the power supply, Eggman demonstrated the power of the Cannon by blowing up half of the Moon.</p>
When Sonic the Hedgehog (along with his friends Tails, Knuckles and Amy) tried to intervene, Eggman stole the seventh Chaos Emerald from them. However, when he inserted the final emerald, rather than activating the full power of the weapon, a recording made by Gerald Robotnik as a last act of revenge appeared on several monitors, and the ARK itself began hurtling towards New Earth. This was Robotnik's revenge plan: when warmongering humans attempted to activate the Eclipse Cannon, the energy from the Chaos Emeralds would be transferred to the engines and the colony would crash into New Earth, destroying all life on the planet.
In an attempt to stop it, Sonic and Knuckles made their way to the core. However, they were waylaid by the Biolizard, which had also been awoken when the seventh emerald had been connected to the Cannon, remembering its creator's lust for revenge against New Earth. At the same time, Téa Gardner and Amy Rose convinced Shadow that Maria's final wish was that he should protect mankind, not destroy it, and Shadow realized that his memories had been tampered with. Shadow quickly went to help by distracting the Biolizard. This allowed Knuckles enough time to deactivate the power of the Chaos Emeralds by using the Master Emerald. However, they were not safe for long, as the Biolizard used Chaos Control to merge with the Colony itself, becoming the Final Hazard, and continued its descent to the planet.
Sonic and Shadow used the power of the Chaos Emeralds to become Super Sonic and Super Shadow, respectively. The two fought and defeated the Final Hazard, then used Chaos Control to teleport the entire colony into a safe orbit from New Earth. However, this used the last of Shadow's strength, and he disappeared falling towards New Earth, happy to have fulfilled Maria's final wish. He was believed dead afterwards, but this would later be disproven.
When told of Shadow's death, Yugi and his friends are devastated, particularly Téa. Even Wolf is heavily shocked by Shadow's death.
The ARK is featured as an old deserted station since the events of
Sonic Adventure 2. When the Black Arms attack New Earth they quickly gained control of the ARK by using Shadow to destroy all the defense systems. Once the ARK was taken over, the Black Arms used the five Emeralds they had to destroy the White House to terrify the humans. It is also here that Shadow remembers the incident in which Maria was killed and a flashback when the Artificial Chaos went on a rampage, and he and Maria had to stop them. Shadow was also confronted here by the Commander of G.U.N. only to discover that he hates Shadow, because he blames Shadow for the death of Maria, his childhood friend. Despite that, he lets Shadow go after realizing Shadow remembers nothing. During the true ending, Team Chaotix had arrived on the ARK, with Espio's terminal system. It is revealed that they were sent to the ARK's main computer room, by an unknown agent to recover some data using five secret disks. However, Espio was having problems until Charmy did what Shadow had done earlier in the game; whack the terminal, which proceeds to activate a hologram of the professor, before he went insane. It reveals to Shadow that he had needed help with Shadow's creation, and Black Doom had agreed to help him with his research, but only if, in the future, when he returns, Shadow would find the seven Chaos Emeralds, and give them to him. However, when he discovered Doom's evil intentions to rule the world, he later built the Eclipse Cannon to destroy the Black Comet. The video gave Shadow confidence in confronting Black Doom, the leader of the Black Arms. The Eclipse cannon is later used by Shadow to destroy the Black Comet, after Devil Doom was defeated. The game closes with Shadow on board the ARK, with a picture of him, Maria, and Professor Gerald.
The Eclipse Cannon (エクリプスキャノン) is the signature weapon of the space colony. It projects a humongous laser (blue in Sonic Adventure 2 and green in Shadow the Hedgehog) that is capable of destroying an entire planet when it is fully charged and powered by all seven Chaos Emeralds. The cannon takes longer to charge with fewer Emeralds.
The main room that assists in powering the cannon is called "The Core." It is a complex system flooded by yellow fluid (safe enough for swimming, as demonstrated by Knuckles), and the fluid leads into a room large enough to well fit the Biolizard. This room contains an architectural copy of the Master Emerald altar, designed for maximum Chaos Emerald energy extraction.