When the dreaded cosmic entity known as the Phoenix Force is revealed to be returning to Earth, the Avengers and the X-Men fight over the fate of Hope Summers, who is expected to become its host. The Avengers believe it will destroy Earth, while the X-Men believe that it would restore the balance of life on the planet by restoring the mutant species. Stark and Henry Pym developed a massive armor to disable or destroy the Phoenix Force, but it results in the Phoenix Force splitting into five parts, each seeking out one of the X-Men.