The Xavier Mansion is a large house used as a headquarters for the X-Men.
Below the surface he built complex technology including Cerebro, which he uses to locate other mutants, and the Danger Room, which uses holograms and robots that he uses to train his X-Men. The mansion has several defenses located outside that is controlled by Cerebro.
Xavier invited Kitty Pryde to the mansion train her so she could control her powers and join the X-Men. She arrived in a taxi and went inside. She was greeted by a ghost of Xavier, a mental image he projected to guide her to him. She found him and he began showing her around. He tells her things about herself that she never told anyone. When asked he tells her about Cerebro and the special Mutant Power Circuit.
Xavier then showed her the Danger Room where his X-Men were training. He showed her Scott Summers also called Cyclops, who can shoot concentrated beams of pure energy from his eyes. Then there was Peter Rasputin also called Colossus, who is impervious to harm. Next was Alison Blaire also called Dazzler, who can transform sound into powerful bolts of light. Kitty then spotted Nightcrawler, who has mastered the art of line of sight teleportation. The next to show up was Wolverine, who has razor sharp adamantium claws. Then it was Storm's turn, who can control the weather. He then stated that his power is to see into people's minds, but he does not do this recklessly.
Xavier then invited his X-Men up to the control room to meet Kitty. Nightcrawler was the first to appear since he teleported in. His appearance frightened her and she phased through the control computer shorting it out. She met the other X-Men, however Wolverine didn't feel that a kid is ready to join. Then a red alarm went off, it was a mutant threat. The team left and Kitty followed.
The X-Men got into two jets and leave for the Deep Space Observatory. Meanwhile, they were being watched by Magneto and Juggernaut. Together the two destroyed the Mansion's defenses. Kitty and Xavier watched on monitors while he explained that Magneto is the master of magnetism while Juggernaut is Xavier's step-brother. 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 Cerebro's Mutant Power 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 confronted 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 returned to Juggernaut.
The X-Men arrived back at the mansion in ruins and pulled Xavier out from under a pile of rubble. Kitty woke up to find Nightcrawler staring down at her. She freaked out but was comforted by Dazzler. Kitty got into an argument with Wolverine before she wondered where Xavier was. Xavier showed that he was alright.
Xavier then used his powers to find discover what Magneto was doing. On Asteroid M Magneto had successfully installed the Mutant Power Circuit and was diverting the Scorpio Comet towards Earth. It would have killed most of the human race so that mutants could rule. The power of the energy involved knocked Xavier to the ground.
Xavier told his X-Men of Magneto's plan and that they had to stop it. Kitty wanted to come but both Wolverine and Xavier agreed that she should stay as she had not been trained yet. Kitty refused to be left behind and followed.