New X-Men By Grant Morrison Vol. 2: Imperial

Collects New X-Men (2001) #118-126. John Sublime and his U-Men launch an attack on the X-Men while a villain thought long gone makes their reappearance, 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!