New X-Men Vol. 2: Imperial
Grant Morrison (Writer); Frank Quitely, Igor Kordey, Ethan Van Sciver, and Tom Derenick (Artists)
As protesters lay siege to the Xavier Institute, Professor X lies in a coma -- trapped within the shattered form of his evil twin! Cassandra Nova, the psionic psychopath inhabiting Xavier's body, has returned to Earth -- with the might of the entire Shi'ar Imperium!
New X-Men (1st series) #118-126