Magneto knew about the circuit and wanted to use his for a plan. Magneto set a plan into motion to steal the circuit.
Magneto sent Blob and Pyro to the Deep Space Observatory to distract the X-Men while he and Juggernaut attack the Xavier Mansion to acquire the circuit. It worked and the X-Men departed leaving Xavier and Kitty Pryde behind.
Together the two destroyed the Mansion's defenses while Kitty and Xavier watched on monitors. Too worried to notice, Kitty phased through Cerebro's defensive circuits allowing the two evil mutants to enter.
Xavier scanned Magneto's mind and learned that he came for the circuit. Xavier handed the circuit to Kitty just as the two attackers entered. Using her powers she ran off with Magneto in hot pursuit while Juggernaut confronts his step-brother. Magneto used electrical cables to shock Kitty into dropping the circuit and phasing through the floor. He picked up the circuit and returns to Juggernaut.
After recovering Xavier then used his powers to find and discover what Magneto was doing. On Asteroid M Magneto had successfully installed the Mutant Power Circuit, using it to amplify his powers and divert the Scorpio Comet towards Earth. It would have killed most of the human race so that mutants can rule.
The X-Men attacked the asteroid and Nightcrawler found Magneto who only taunted him. He tried to destroy Nightcrawler but Kitty phased up through the floor to stop him. Magneto was further distracted when a dragon bit his ankle. Magneto accidentally broke the circuit, which meant that nothing could change the comet's course. However, Xavier told Nightcrawler to complete the circuit while Kitty pushed Magneto back onto the platform. The resulting energies pushes away the Scorpio Comet, but sent it towards Asteroid M.
However, Nightcrawler had to continue completing the circuit or else the comet would head back towards Earth. Magneto then left with the Brotherhood back to Earth. The X-Men left in the Blackbird while Nightcrawler teleported away at the last second. The comet hit the asteroid and the circuit was destroyed once and for all.
This is the first and only appearance of the Mutant Power Circuit as it was created specifically for the episode.