One Below All

The Below-Place is the source of the mutagenic third form of gamma energy, an emanation of the One-Below All, and is thereby capable of using gamma mutates to manifest. The One Below All has existed for at least before the current version of the Multiverse (as it saw Galan of Ta become Galactus) and most likely well before as in an alternate future, it and the Below-Place survived unchanged into the ninth iteration of the Multiverse. The One Below All is a creature without a mind of its own, possessing only terrible desires. The ultimate goal of the One Below All is to destroy everything in the Multiverse, and to become the one remaining presence in it.

During his research into the properties of gamma radiation, Brian Banner had a dream-vision of the One Below All, and sensed the creature looking for him. This experience prompted him to put all of his research to a halt. When Brian's son Bruce investigated gamma radiation on his own, he developed a powerful Gamma Bomb. The bomb's explosion opened the first Green Door, a metaphysical barrier into the Below-Place, and infused him with gamma radiation, turning him into the Hulk.

Years later, when Bruce killed Brian during the Chaos War, his soul was plunged into the Below-Place. Since the One Below All couldn't directly influence the real world and needed a personality to work through, it started using Brian's soul as its vessel. Through a Green Door, Brian possessed the gamma mutate Jailbait, causing her powers to go out of control. Her boyfriend, Hotshot, then was forced to tie her to a chair, due to her power growing out of control. He went to a church during Sunday services and held the congregation hostage in order to force the priest to perform last rites on Jailbait. He was ranting that Jailbait was possessed by the devil and that he saw a green door.

When Sasquatch was killed in a bar fight, Brian possessed him next and sent him on a feral rampage. The Hulk intervened and drained Walter's gamma power to stop him, which inadvertedly passed Brian's possession onto him. The One Below All had Brian nudge the Hulk into travelling to the Los Diablos Military Base, the place where the gamma bomb had detonated. The Hulk saw through the One Below All's plan, but when Absorbing Man intercepted him, he drained the Hulk's gamma energy, transferring the possession to himself. After a brief battle with a now-emaciated Hulk, Gamma Flight arrived and Absorbing Man's possessed corpse used the distraction to flee towards the area where the original gamma bomb had been detonated, absorbing all the ambient gamma energy in the area. Successful, the One Below All opened a Green Door and plunged everybody on the scene into the Below-Place.

When the Hulk arrived at the Below-Place, he was split from Bruce Banner, whom Brian took captive with the intention to make him the new vessel for the One Below All and bring the Earth to Below-Place. While making his way through the Below-Place, the Hulk was confronted by manifestations of Rick Jones and Thaddeus Ross, enraging him to the point where his Savage Hulk personality briefly emerged. When the sun rose, the One Below All was able to appear in an ominous cloud-like form and was soon ready to take control of Bruce's body.

The One Below All summoned a horde of demons whom the Hulk confronted along with the Rick Jones manifestation. In the meantime, Gamma Flight member Puck had managed to convince the Absorbing Man to set things right, and they approached Brian in the fountain of gamma energy where he was holding Bruce. The Absorbing Man soaked up the gamma energy and transferred it into the Hulk, allowing him to regain his strength just as he was being overwhelmed by the demons. Hulk then unleashed a thunderclap that dispersed the One Below All. With his power regained, the Hulk merged back with Bruce and closed the Green Door, sending everybody on the scene back to Earth.

In the far future, the One Below All managed to destroy the soul of Bruce Banner and possessed the body of the Hulk. It then went on to kill the likes of Franklin Richards, Galactus, Mister Immortal, and many others, thus becoming the only being left in the universe. When the Sentience of the Eighth Cosmos came to greet what he thought was Bruce Banner, he soon discovered that that it was an elaborate trick and the One Below All-possessed Hulk then quickly devoured the being and absorbed its power.

In the newly formed Ninth Cosmos, the One Below All used the power of the recently devoured Metatron to transform the possessed Hulk into a Galactus-like being named the "Breaker of Worlds." Ten billion years later, the Breaker of Worlds destroyed all life, light, and planets in the cosmos, effectively rending it dead. When the alien, Par%l, tried to make contact with the Breaker of Worlds to attempt to reason with it, the alien instead met the abstract form of the One Below All which told hir it wanted to "Make all hollow as I, dark and dead as I" and killed Par%l. Destroying all life in the Multiverse, he finally achieved his ultimate goal.

In the present, the gamma-mutated villain Leader became aware of the One Below All's ultimate victory though a warning sent back in time by Par%l. Having been investigating the Below-Place and the Green Door, the Leader set out to help bring this dire future into being. Sterns managed to open a Green Door and assimilate Brian's soul into himself, obtaining his connection with the One Below All. With it and the ability to possess and manipulate gamma mutates, the Leader embarked on a plan to fulfill the One Below All's goal to break Bruce Banner.

Leader managed to enter Banner's mindscape and force Banner and the remains of the Devil Hulk persona into the Below-Place. He hooked them up to strange, plant-like structures so they could act as a device to channel gamma energy into the One Below All. However, Leader couldn't get the device to work, even though Brian Banner could. Then Leader learned the truth from Brian Banner's spirit: Brian could do it because he was possessed by the One Below All, something Leader didn't want. After that, the One Below All possessed the Leader, much to his horror.