After a giant egg arrived on Earth from space, a being later called the Apocalypse Beast hatched from it. The huge newborn creature found and fed on strange egg-shaped organic material, which somehow reacted with the Beast's system and rendered it unconscious. The Deviants, an offshoot of humanity created by the Celestials, used this opportunity to send the weakened creature into another dimension. Afterwards, they genetically engineered a race of beings known as the Moloids and apparently spliced the organic material into the Moloids' genetic makeup should the Apocalypse Beast return. The Moloids were located on an island (later dubbed Monster Island, linked to Subterranea), where the Deviants left machinery that the Moloids would one day know how to use upon the Beast's return.

Recently, Tokyo Giant Monster Museum and Expo Center curator Dr. Yamane, the son of a cultist who worshipped the beast, began a process to return the Beast to Earth. Many of earth's giant monsters (including Deviant mutates, the ancient dragon Grogg and the Atlantean creature Giganto, as well as the science-created lizard monster Droom) sensed the Beast's impending return and went berserk, rampaging through Tokyo before being stopped by the Fantastic Four and Iron Man (who had been touring the museum). Grogg calmed the rest of the monsters and led them away after Mr. Fantastic promised the heroes would stop the Apocalypse Beast. The heroes and Yamane traveled to the North Pole, where they discovered an organic structure in which Shadow Men from the Kaa dimension prepared for the Beast's arrival. Yamane betrayed the heroes, using himself as a key to let the Beast rip through the dimensional barrier. Emerging from its prison, it destroyed the structure before stepping on Yamane. Fully grown now, the Beast instinctively made its way to Monster Island, crossing the whole of Japan in just a few steps, as it sensed the Moloids' DNA was also infused with part of the monster. As the heroes and the Moloids' human master Mole Man tried to stop the monster, the Moloids stopped serving their usual leader and began to prepare for the Beast's arrival. Mr. Fantastic attempted to decipher ancient Deviant paintings regarding the Beast while Iron Man and Invisible Woman entered the creature's system and battled giant antibodies. Just as Mr. Fantastic realized that Monster Island was effectively designed to replicate the functions of a giant syringe, the Beast arrived at the island. The Moloids and heroes activated the Deviants' long-abandoned machines, and many Moloids injected themselves into the Beast's body. Inside the Moloids attacked the Beast's immune system, killing the Beast and turning its body inside out before being launched into space.

In at least one future reality (Earth-6034), by the year 12425 AD, the Moloids who inhabited the Beast's body used it as a floating planet. They created a new civilization for themselves until they finally depleted the resources found in the Beast's body. With only two Moloids and their newborn son left alive, the parents opted to launch the son, Noah, into space as their world died around them, in order to let him find his own place in the universe.