"Necrosha" is an underrated story that is a victim of bad timing. Resurrected by former Hellfire Club Black Queen Selene using a corrupting techno-organing virus, friend and foe alike are brought back from beyond the grave to attack the X-Men on Utopia. Selene, meanwhile, readies to feed on the souls of millions of dead mutants massacred on the island nation of Genosha years prior, which would transform her into a God. It's a violent, vile, gripping tale with two very well done parallel stories and a complex backdrop that touches on decades worth of material.
