It all started with a flash in the sky and a ripple through the clouds. Nobody knew what exactly caused this, but some think it might have been a punch. The hunger had made the unknown super hero so determined to satisfy his hunger that he ripped a hole in the very fabric of reality.
When the zombified Mister Fantastic's plan to lure his other dimensional counterpart to their world failed, and Magneto destroyed the machine that made dimensional travel possible, the zombified superhumans needed sustenance. When the Silver Surfer arrived to inform the zombies that Galactus would shortly be arriving to consume their world, they attacked him, and after a short battle he was defeated and devoured by the zombies, each gaining some of the power cosmic, and apparently killing the Surfer.
The zombies then devised a way to attack Galactus using a machine that would combine their cosmic blasts. It seriously hurt Galactus, and they then had a skirmish with the villains in which they easily defeated them with their newfound power. They each ate a portion of Galactus, in turn becoming like him. They then set of to consume and destroy the universe they once fought so valiantly to protect.