Domino was a mercenary who was contacted by Charles Xavier along with her partner Cable to hack into Cyberspace in order to rescue Erik Lensherr from being used and corrupted by the government's new Hunter robot Nimrod.
As Domino uploaded herself into the system she took a cycle to penetrate Lensherr's base Asteroid M. But once inside she was attacked by Nimrod who had been waiting for her to show up. Domino used her probability powers against the hunter as it began to replicate itself into multiple viral bodies to attack her.
She dodged it's concussive blasts and with a little lucky push she was able to fire rounds from her gun which took out Nimrod's main body allowing her a little more time to complete her mission. As she broke off the main door to Lensherr's mind, Domino was confronted by a child-like avatar of Lensherr who revealed to her that he was the one behind Nimrod's creation and that it allowed for him time to finish his machine that would change anyone logging into the system to become exes.
Lensherr then used his magnetic powers to suspend Domino in the air causing her great pain which started to affect her body in the real world. Cable sent out a mental cry to Xavier so he could help Domino as she was the one that believed in his dream. Xavier answered by telepathically sending his astral form in cyberspace to confront Lensherr. After a quick exchange of words Charles touched Erik on the forehead causing an energy feedback that destroyed the tower of Asteroid M but also releasing Domino so she could unplug herself from the system.
As she woke up, she was surrounded by Cable and a revived Lensherr who asked Domino if she was alright. Neena was about to scold him but Cable stopped her realizing that Xavier killed Lensherr's conscious allowing for him to take over his physical form. Charles told them that he did what he felt was needed to help fight this war and asked the both of them to join others like themselves as members of a unit he put together called the X-Men.