During the Astonishing X-Men series, Kitty Pryde saved the world by bonding herself with Breakworld’s giant bullet which was on its way to Earth. She made the entire thing become intangible but in the process trapped herself with the bullet to wander space endlessly.
Her exile was ended by Magneto when he used his magnetic powers to bring the bullet safely to Earth, in a bid to prove to Cyclops that he was sincere in joining the X-men. The happy reunion was only mired by the horrible fact that Kitty couldn’t phase back into tangibility anymore.
Shortly after Kitty’s return, refugees from Breakworld led by former-Powerlord Kruun, came to Earth and was granted sanctuary by Cyclops on Utopia. It was a ruse by Kruun to take revenge on the X-Men for ruining their society during their adventure in Breakworld.
Kruun’s partner, Haleena, seemingly killed Kitty Pryde. She then used Breakworld’s technology of transferring one’s life force to resurrect another, thereby making Kitty whole again.