Marvel's two mightiest teams clash over the fate of Hope Summers, the Mutant Messiah, in this unbelievable crossover series. The Avengers and the X-Men have stood united countless times in the past, battling together against rogue space tyrants, mad mutant demagogues, and near-omnipotent otherwordly entities. Now, any former frienships and alliances are about to be torn apart, as the almighty Phoenix Force returns to Earth, destroying everything in its blazing wake.