The X-Men confront the Inhumans in the most uncanny conflict of all! Since the discovery that the Terrigen Mists - the key to unlocking an Inhuman's hidden potential and powers - are lethal to mutants, the X-Men and Inhumans have been locked in a cold war. But now things are heating up, and about to boil over! As the Terrigen seeps into the Earth and reaches an irreversible tipping point, the X-Men are spurred into action to ensure the future of their species! And for Jean Grey and Fantomex, this means taking out of commission the Inhumans' deadliest weapon: Karnak! The Marvel Universe will be rocked by IVX!