Sonic Adventure 1Edit
Three thousand years ago, the echidna empire, ruled by Pachacamac, desires the Chaos Emeralds and the Master Emerald - mysterious emeralds with unlimited power. Pachacamac's daughter Tikal befriends the Chao in the emeralds' shrine and their guardian Chaos, a water-based creature. Tikal tries to explain to her father that attacking the shrine and killing the Chao to gain possession of the emeralds is not the way to peace, but Pachamac and his men do so anyway. He and his men, however, did not know about Chaos, the guardian of the shrine, and the enraged Chaos uses the power of the emeralds to transform into Perfect Chaos and destroy the echidna empire. Tikal survives and seals the angered Chaos and herself inside the Master Emerald for eternity.
In the present day, Knuckles the Echidna is guarding the Master Emerald on the floating Angel Island when Chaos is released from the emerald by Dr. Robotnik. The Master Emerald, now shattered, can no longer keep Angel Island afloat, and Angel Island plunges into the sea, scattering the shards of the Master Emerald and all the Chaos Emeralds. The Chaos monster later appears in Station Square, and is confronted by Sonic the Hedgehog, who defeats him in a fight. Knuckles sets off searching for the shards of the Master Emerald. The next day, Sonic rescues Miles "Tails" Prower after Tails crash-lands in the city while testing his Chaos Emerald-powered plane. They go to Tails's workshop in the Mystic Ruins, where Dr. Robotnik appears with Chaos. Dr. Robotnik feeds Tails' emerald to Chaos, transforming Chaos into a stronger form; Dr. Robotnik explains that Chaos will grow stronger with each emerald he eats and will eventually become invincible and destroy Station Square for him. Upon the ruins of Station Square, Robotnik intends to build Robotnikland, where he will rule it all. Sonic and Tails set off searching for emeralds to prevent Robotnik from getting them first, but eventually lose the ones they find to Dr. Robotnik and Chaos. Dr. Robotnik escapes in his flying fortress, the Egg Carrier, which shoots down Sonic and Tails's pursuing plane.
Dr. Robotnik orders his E-Series robots, including E-102 Gamma, to search for Froggy, a frog who has eaten Chaos's tail as well as a Chaos Emerald. Gamma finds Froggy but is chased by Froggy's owner Big the Cat back to the Egg Carrier. Meanwhile, Tails finds another emerald and uses it to prepare the Tornado II plane to find Sonic. Sonic lands in Station Square, where he runs into Amy Rose, who insists on protecting a Flicky bird she found, named Birdy. One of Robotnik's robots, Zero, intends to get the bird back from Amy and continually chases her. Zero finally captures Amy and Birdy, and escapes to the Egg Carrier. Sonic and Tails board the Tornado II and manage to board the Egg Carrier. Knuckles also boards the aircraft after collecting pieces of the Master Emerald and seeing an image of the Egg Carrier in the emerald.
On board the Egg Carrier, Dr. Robotnik commands Gamma to go tend to Amy. Gamma wanders into the wrong room and witnesses his brother E-101 Beta being rebuilt, and leaves to go to the other room. Here, Amy convinces Gamma that Robotnik is a bad man and that Gamma shouldn't work for him. In a confusion of newly discovered emotions, Gamma allows Amy and Birdy to leave their prison; Amy goes on deck.
Here, she runs into Sonic and Tails, who confront Dr. Robotnik. Robotnik flees down the ship, Sonic fight's Gamma but spares him at Amy's request. At this time, Gamma fully understands that Robotnik is a bad person and that he should follow the others instead. Tails, Amy, and Gamma evacuate the ship, and Sonic and Knuckles go chase Robotnik down. Here, they fight Chaos, who now has all but one of the seven Chaos Emeralds. The Egg Carrier begins to malfunction and lose altitude, and Sonic, Knuckles, Big, and Robotnik evacuate the ship as well.
Gamma decides to track down his brother robots and destroy them to free the animals inside, and eventually confronts his elder brother E-101 Beta, in his rebuilt form, on the Egg Carrier. Gamma defeats Beta but is wounded in the process, both robots exploding, and each releasing a Flicky bird. Birdy reunites with its friends when Amy visits the ship. Sonic and Tails, meanwhile, defeat Robotnik in the Egg Viper and Egg Walker, respectively.
A day later, Knuckles restores all the shards of the Master Emerald, but Angel Island collapses into the sea again when Chaos attacks him and Dr. Robotnik. Chaos absorbs the 6 Chaos Emeralds and locates the seventh aboard the Tornado II, which crashed after Big used it to escape the Egg Carrier. With all the Chaos Emeralds, Chaos transforms into Perfect Chaos, depleting the Chaos Emeralds of their negative energy, and flooding and destroying Station Square. Tikal appears, having taken each main character into the past numerous times beforehand, demanding that Chaos must be sealed back in the Master Emerald. Sonic objects, saying that Chaos's heart would still be filled with anger and sadness if he were to be sealed inside the Master Emerald. Sonic's friends cheer him on, and Sonic uses the Chaos Emeralds' still-present positive energy to become Super Sonic. Sonic defeats Perfect Chaos, and Chaos survives in his basic form. He discovers that the Chao he once was guardian of now live in Station Square, so he leaves them on Earth to live there, while Chaos himself peacefully departs to the past with Tikal. Dr. Robotnik flees the scene, with Sonic pursuing him.
Sonic Adventure 2
After discovering the existence of a secret weapon mentioned in the diary of his grandfather, Gerald Robotnik, Dr. Eggman infiltrates a high-security G.U.N. facility in search of it. This "weapon," a black hedgehog named Shadow who claims that he is the "Ultimate Life Form," offers to help Eggman take over the world, telling the scientist to rendezvous with him at the abandoned Space Colony ARK with more Chaos Emeralds. Shadow proceeds in stealing one of the emeralds, and G.U.N. officials mistake him for Sonic. Shadow has a flashback during these events to the final moments of a young girl named "Maria," begging him to do an unspecified task—which he interprets as a request for revenge. Sonic is arrested shortly after he confronts Shadow, who demonstrates to Sonic the Chaos Control technique.
Meanwhile, Knuckles confronts both Rouge the Bat and Eggman, who each attempt to steal the Master Emerald. Knuckles shatters the Master Emerald to prevent this, and proceeds to search for the scattered shards and restore the Emerald. While Rouge also intends to collect the shards for personal benefit, she must also accomplish a mission for the government to spy on Eggman. This mission causes her to infiltrate Dr.Eggman's base, which also leads her to the ARK, where Shadow relays to Eggman his plan to use the Chaos Emeralds to charge a "super weapon" on the ARK called the Eclipse Cannon to take over the world. To accomplish this, Shadow and Eggman recruit Rouge to assist in the search of the Chaos Emeralds.
Tails and Amy infiltrate Prison Island and rescue Sonic from G.U.N., while Eggman, Shadow, and Rouge collect three Emeralds on the island, which they then destroy. Eggman then broadcasts his threats across the planet and demonstrates the cannon's level of power by destroying half of the moon. Sonic and company use the final Emerald within their possession to track down the other six, with Knuckles coming along as well. Together, the group infiltrates Eggman's base, narrowly boarding Eggman's shuttle as it launches into space. Along the ride into space, Knuckles' Master Emerald shards are spilled, and he leaves the group to collect them, encountering Rouge again. During the fight, Knuckles saves Rouge from certain death, and Rouge surrenders her collected shards, finally allowing Knuckles to restore the Master Emerald.
On board the ARK, Tails reveals that he has created a counterfeit Chaos Emerald designed to reverse the effects of the real Emeralds and destroy the Eclipse Cannon. Sonic goes to place the fake Emerald into the cannon when Eggman announces he has captured Tails and Amy. Sonic tries to give Eggman the fake Emerald, but at the last second Eggman traps and jettisons Sonic in an escape pod rigged with explosives. Using the fake Emerald, Sonic manages to perform Chaos Control and escape before it explodes, but Tails, thinking Sonic is dead, fights Eggman again. Shadow is sent to intercept Sonic before he destroys the Eclipse Cannon, but Sonic succeeds.
Once Eggman collects all seven Chaos Emeralds and attempts to fire the Eclipse Cannon at full power, a failsafe activates, and a recorded message is broadcast by the late Gerald Robotnik. It explains that the ARK will collide with and destroy Earth, as revenge against humanity for condemning him and his research, as well as killing his granddaughter Maria and numerous colleagues on board the ARK. Everyone agrees to work together to neutralize the Chaos Emeralds with the Master Emerald and stop the collision. Shadow initially does not participate, due to his apathy for humankind, however Amy's pleading reminds him of Maria's true request to serve as a benefit for society. He catches up with Sonic and Knuckles after they make their way to the core.
After disabling the various security features guarding the Cannon's core, Sonic and Knuckles encounter the Biolizard, a prototype of the Ultimate Life Form, and Shadow's "biological" brother, who had been awoken from stasis to ensure that the Emeralds would not be tampered with. Shadow defeats the Biolizard, allowing Knuckles to deactivate the Chaos Emeralds using his repaired Master Emerald. However, the injured Biolizard uses Chaos Control to fuse with the Eclipse Cannon, becoming the Finalhazard and continuing the ARK's collision course by physically dragging it along. Using the power of the Chaos Emeralds, Sonic and Shadow transform into Super Sonic and Super Shadow and defeat the Biolizard while he is fused to the ARK. They then use Chaos Control to teleport the ARK back into a stable orbit around Earth. The process, however, depletes Shadow's energy, and he is unable to remain in orbit. He plummets to Earth, and to his apparent death, content that he has fulfilled his promise to Maria. Humanity celebrates openly as the two teams solemnly express gratitude towards Shadow for his sacrifice and return to Earth, expressing their plans from there.