Sonic Adventure 2

After learning about a secret weapon from the diary of his late grandfather, Professor Gerald Robotnik, Eggman infiltrates a high-security G.U.N. facility to find it, and uses a Chaos Emerald to free it.[16] This weapon, a black hedgehog and self-proclaimed "Ultimate Life Form" named Shadow, offers to help Eggman take over the world, telling him to rendezvous at the abandoned Space Colony ARK with more Chaos Emeralds. Shadow then goes to Central City, where he steals a second Emerald and encounters some soldiers of the military group G.U.N. He flashes back to the death of a girl, Maria, who begs him to fulfill an unspecified promise he interprets as one of revenge. Shadow blasts through the military force and meets Sonic, who the military mistook for Shadow. After a brief confrontation, Shadow escapes and G.U.N. captures Sonic.

Knuckles and Rouge are fighting over the Master Emerald, when Eggman suddenly grabs the Master Emerald with a large claw, and begins to fly off in his Eggmobile. After Knuckles leaps into the air, shattering the Emerald to prevent this, he looks for the scattered shards.[17] Rouge intends to collect the shards for herself, but - as a government spy - she also must spy on Eggman. This mission leads her to Eggman's base[18] and, eventually, the ARK. On board, Shadow shows Eggman a superweapon known as the Eclipse Cannon, also created by Gerald Robotnik. Shadow discloses the plan: to charge the Eclipse Cannon with Chaos Emeralds and use it to take over the world. Rouge appears and feigns her allegiance to Shadow and Eggman, offering them a third Emerald to gain their trust.

Tails and Amy infiltrate G.U.N.'s island base and rescue Sonic,[19] while Eggman, Shadow and Rouge collect three more Emeralds on the island before blowing it up. Eggman broadcasts his threat around the world, demonstrating the cannon's power by destroying half of the Moon. Sonic, Tails, Amy and Knuckles use their Chaos Emerald to track down the other six. They infiltrate Eggman's base,[23] boarding his shuttle as it launches into space. Knuckles' Emerald shards are spilled along the way, and he leaves to collect them.[24] He again meets and fights Rouge, but when he saves her from falling into a lava pit, she surrenders her shards and Knuckles restores the Master Emerald.

On the ARK, Tails reveals that he has designed a counterfeit Chaos Emerald to reverse the energy fields of the real ones. Just as Sonic is about to put the fake Emerald into the cannon, Eggman tells him that he has captured Tails and Amy, forcing him to return with the Chaos Emerald and rescue them. Sonic tries to trick Eggman with the fake Emerald, but Eggman traps and jettisons him in an escape pod rigged with explosives. Using the fake, Sonic performs Chaos Control and escapes Tails, thinking Sonic is dead, defeats Eggman, but Eggman sneaks away with the real Emerald when Tails is distracted. Rouge hacks into the ARK's computers for information on the Ultimate Life Form project, suggesting Shadow is not the Ultimate Life Form, and attempts to retake the other Emeralds, but is caught and found out by Shadow before he is sent to stop Sonic from reaching the Eclipse Cannon. Sonic defeats Shadow and uses the fake Emerald to destroy the Cannon.[27]

When Eggman loads the last Emerald into the cannon and tries to fire it at full power, the ARK begins falling toward Earth and a recorded message from Gerald Robotnik, Eggman's grandfather, is broadcast worldwide: he programmed the ARK to inevitably collide with Earth, destroying it in revenge against humanity. His diary reveals that this hatred began when the government condemned his research and killed a number of his colleagues, along with his granddaughter Maria, in an attempt to shut the ARK down, and he programmed his Ultimate Life Form, Shadow, to carry out his plan of revenge. Eggman determines that the Emeralds' energy is making the ARK fall, and everyone works to access the cannon's core and neutralize it.

Shadow declines to help the others, but Amy urges him to help, making him remember Maria's real request: for him to help mankind. With this knowledge, he races for the core, where Sonic and Knuckles encounter the Biolizard, the prototype of the Ultimate Life Form. Shadow arrives and holds it at bay, allowing Knuckles to deactivate the Chaos Emeralds using the Master Emerald. The Biolizard then uses Chaos Control to fuse with the cannon, becoming the Finalhazard and continuing the ARK's collision course.

Sonic and Shadow use the Chaos Emeralds to transform into their super forms, Super Sonic and Super Shadow, defeating the Finalhazard and using Chaos Control to teleport the ARK into a stable orbit around Earth. This depletes Shadow's energy and he plummets to Earth, content that he has fulfilled his promise to Maria, and is presumed dead. As the people of Earth celebrate, the teams reflect on what has happened; as they leave the station, Sonic bids Shadow a final farewell by saying "Sayonara, Shadow the Hedgehog." (C) - SEGA (C) - Nintendo