Ultimate X is a limited series from Marvel Comics written by Jeph Loeb with pencils by Art Adams, originally planned as an ongoing bi-monthly series.The story picks up after the events in Ultimatum and serves as a quasi-sequel/spin-off of Ultimate X-Men. Originally scheduled to be published bi-monthly, alternating months with Loeb's other Ultimate title Ultimate Comics: New Ultimates, X had long repeated delays, and became instead a prologue to Ultimate Comics: X-Men. Source: Wikipedia (en)