History
Hulk was with his fellow teammates at Avengers Tower when the Celestial Exitar the Executioner came to Earth to destroy it after the Apocalypse Twins killed a Celestial Gardener.[1]
In order to try and stop the cosmic being, Hulk helped Iron Man in the construction of a force field generator which was meant to project a shield around the entire planet in hopes that it would hold off Exitar's attacks. But the field only lasted for a short while since the generator couldn't handle the extremely powerful attacks which led to the group's demise and Earth's destruction.[2]