Earth’s Mightiest Heroes battle the Children of the Atom in a crossover so huge it calls for Marvel’s biggest-ever Omnibus! Get the whole story of the Phoenix Force’s return to Earth, an event that kicks off an all-out war between the Avengers and the X-Men! The X-Men see the Phoenix as mutantkind’s salvation, and the Avengers consider it a deadly danger. But what happens when five of the X-Men are transformed by the Phoenix and begin to change the world?