While almost everyone else was getting messed with by Loki, X-Factor went out to space to meet the Celestials on a planet where, basically, super-mutants had been the dominant lifeform. It starts when their living ship, which they took from Apocalypse, is “kidnapped” with the X-Factor folks on board. The ship was taken by a Celestial—and by the end of the arc we learn that Ship was actually created by the Celestials. And you can see above how big he is!
They go to a planet that is going through a Celestial experiment/race war between “rejects,” “perfects,” “begin-agains,” etc., and the members of X-Factor end up getting split up and going with different groups.
Yeah, we’ve seen stuff like this before in X-Men books, it’s pretty heavy handed and not all that novel.
Along the way, Jean Grey has repeated issues with her “Madelyne” and “Dark Phoenix” personalities taking over. This feels very similar to Rogue’s internal conflicts with Carol Danvers’ personality—and having two characters in mutant books wrestling with the same issues doesn’t do much for readers. So, this gets resolved by having her reconcile her internal conflicts—in a fairly perfunctory way—and eliminating the Madelyne personality by the end of this arc. Basically, in order to free X-Factor and defeat the Celestials, Jean “uses up” those other personalities. No, it doesn’t make sense that using her powers would burn away other personalities—but it doesn’t have to. Because we get to a good result in the end.
Also, baby Cable starts to demonstrate some of his super powers. That’s neat.
There’s also a weird flashback story that focuses on Angel, takes place on Earth, and Marvel Assistant Editor Greg Wright makes an appearance.
There’s also a brief cameo by Professor X and the Starjammers. I guess that happens because X-Factor is in space, and so are the Starjammers, so, why not?
Also, Loki invites Apocalypse to join the Acts of Vengeance event, and Apocalypse says no thank you.
Then they fight for a bit. So, technically X-Factor does participate in Acts of Vengeance.
Creators: Louise Simonson (script #43-47, 49-50), Paul Smith (art #43-47, 49), Kieron Dwyer (script and art #48), and Rich Buckler (art #50)