Mecha

Eggman had conquered most of Mobius during Sonic's year long absence in space. Because he had so much power, it was inevitable that Eggman would need a soldier to guard him at all costs. Mecha would make her presence known when Sonic and Tails arrived to stop Eggman from launching nuclear missles at Knothole and Station Square. While Tails tried to keep A.D.A.M. busy, Mecha gave Sonic a thrashing for attacking Eggman. Her orders were to make sure Sonic is stopped. Sonic managed to lead her away from Eggman's ship and caused her to waste much of her fuel by continuously dodging her laser optics. She did get a lucky shot and would have killed Sonic had Bunnie Rabbot not knocked her away, ruining her outer shell, leaving only a skeletal construct. While Bunnie and Antoine took off to stop Eggman, Mecha recovered to attack Sonic, Espio the Chameleon, Geoffrey St. John, Fiona Fox, and Hershey Cat. The fight ended when Sonic used his speed to carve a circle of road out from under Mecha, causing her to fall into the sewers and short circuit. To make matters worse, her absence allowed Shadow the Hedgehog to pummel Eggman before Bunnie destroyed the nuclear missiles.

Despite this, she was later seen volunteering for an assault on Angel Island after Sonic, Knuckles the Echidna and the Chaotix started devastating the work of Kage Von Stryker. Eggman had a different operative in mind, though.

Mecha remained out of sight until much later when she was seen watching over Metal Sonic's attempt to acquire information on Project: Shadow. Shadow showed up seeking the same information and fought Metal Sonic until they knocked each other out. Mecha took them away. She later interrupted a meeting between Eggman, Sonic and Rotor regarding a potential assassination attempt. Unfortunately, she was somehow under control of the unseen assassin, who sent roughly 100 Metal Sonic Troopers to kill Eggman. Mecha knocked out Sonic and Rotor and had Eggman cornered, while A.D.A.M. became somewhat unresponsive. Eggman managed to override the unknown villian's control over Mecha and fled, finding Shadow and the broken Metal Sonic in the process. Mecha stayed with Eggman while Shadow helped Sonic and Knuckles the Echidna stop the Metal Sonic Troopers. This fiasco would eventually cause Eggman to trace the mastermind to an upstart called "Anonymous." Whether Mecha was controlled by "Anonymous" is unknown.

The Anonymous investigation was still unfinished when Eggman explained to Mecha why he used the Egg Grape Chamber the way he did. Just as Eggman finished his mass killings, The Arachne attacked intending to use the Sword of Acorns to open the Zone of Silence and release Ixis Naugus. Mecha tried to zap the Arachne with her optic lasers, but her aim was awful, and she nearly hit Eggman. Frustrated, Eggman ordered Mecha to take him out of the chamber and had A.D.A.M. trap the Arachne inside, exactly as "Anonymous" hoped. When they reentered the Egg Grape Chamber, Naugus was now present. Mecha tried to blast him, but he vaporized himself, them attempted to asphyxiate Mecha. Of course, since robots don't breathe, Naugus found the trick useless, so he froze her lubricants and warped out of New Megaopolis.

Just as Mecha finished defrosting, A.D.A.M. showed a video of her conspiring with "Anonymous", with "Anonymous's" identity (as usual) obscured so that Eggman could not identify him. Mecha found herself unable to explain this and claimed that A.D.A.M. was lying. Unable to prove her innocence, she had no choice but to obey Eggman's order to self-destruct. Eggman then ordered A.D.A.M. to delete all of Mecha's back-up files so that she would never return. Still, he showed deep regret with having her destroyed, when he told Sonic that he lost a lot thanks to Naugus, Mammoth Mogul and "Anonymous".