Collects Age of X Alpha (2011) #1, X-Men Legacy (2008) #245-247, New
Mutants (2009) 22-24, Age of X: Universe (2011) #1-2. The biggest and
best adventures of Marvel's mighty mutants - these are the X-Men
Milestones! In a world where the X-Men never existed and mutantkind has
been hunted to extinction, the few remaining Homo superior have banded
together to make their last stand. The weary mutants spend each day
securing the walls of their stronghold, Fortress X, in a seemingly
endless battle to beat back the anti-mutant forces that would see them
wiped out. But when a conspiracy is discovered within Fortress X itself,
could it be that mutantkind's last bastion will crumble from the inside
out? When the dust settles, no one will be left unscathed - but what is
the terrible truth about the Age of X?