Greystone was a member of the Xavier Security Enforcers (or X.S.E.) before he started his own group together with teammates Fixx and Archer, namely the Xavier's Underground Enforcers. Greystone and teammates Archer and Fixx all originated from Bishop's timeline in the future. He and his teammates escaped back to the past (the present day of the Earth-616 timeline) and joined X-Factor. During his time with X-factor, Greystone started acting more radical and strange. His grip on reality faded soon, and he became a danger to his former teammates of the X.U.E. and his new teammates of X-factor. Eventually he was certain that it was necessary to detonate a time-altering bomb in an airplane, trying to stop certain things from happening, so that the future might be safe. The X-man Havok was able to stop the mad Greystone, but the bomb went off anyway. Teleporting Havok into the "Mutant X" time-line, but almost certainly killing Greystone. Both teams thought their teammates to have perished, although Havok returned a few years later and returned to the X-men.
Greystone can enlarge himself into an enormous size, which proportionately boosts his strength but gives him a monstrous appearance.