In 2004, Marvel used the title Astonishing X-Men for an ongoing X-Men series written by Joss Whedon and illustrated by John Cassaday. It is a continuation of Grant Morrison's New X-Men title and features a similar line-up of characters, including Cyclops and Emma Frost (as co-team leaders), Beast, Kitty Pryde, Colossus, Lockheed and Wolverine. This team became the usual focus for most X-Men limited series published during Whedon's run as well.
Whedon/Cassaday's Astonishing X-Men run introduced a number of original characters into the Marvel Universe including Kavita Rao, Special Agent Brand, S.W.O.R.D., Hisako Ichiki, Ord of the Breakworld and Blindfold. Whedon's run on the series was a critical and commercial success. The roster of the book was also the focus of various limited series at the time, such as X-Men: Phoenix—Endsong, X-Men: Phoenix—Warsong and World War Hulk: X-Men.
The series is noted for its independence from crossovers and large scale events in the Marvel Universe such as House of M, Decimation, Civil War, Messiah Complex, Avengers Vs. X-Men, and Battle of the Atom. This was previously due to the long delays between issues and Whedon's own stated desire to remain away from big crossovers, which he personally disliked, and what he saw as hectic and unfollowable X-Men continuity, but have persisted almost to the end of the series, with the sole exception being the "X-Termination" event in 2013.