HE was a being of unparalleled power. The creator of the very Universe, and the planet the so-called "Gods" that roam today. Although there were many different pantheons that manifested during his absence (A Millennia of rest needed to adjust to the use of HIS ever growing power) there were 5 main pantheons with the most power that still exist and have not faded back into The Void that is HIM.
The Roman/Greek of the West.
The Norse of the North
The Egyptian of the South.
The Shinto of the East.
The Buddhist in the Center.
The West, North, South and East, had equal amounts of power and influence due to having similar numbers and mortals in their respective lands. The Buddhist were the strongest, however they believed in Peace unless provoked, so the balance of power relatively stays intact. HE allowed all of them to remain in power because he believed that they would make the right decisions as his descendants. HE was so very wrong.
When HE saw the mess that was being made of HIS creation He sent an aspect of HIMSELF to bear their wrongs and correct them with HIS own blood.
While HE succeeded with the mortals, the other Pantheons simply saw HIM as a threat. The Greeks/Romans especially took issue to HIM, so they had HIM slain using their mortal followers. It only helped spread his message of peace and love to the mortals even further as HE could have eradicated them for their sins, but chose not to.
HE was the "father" of the Greek Primordials. HE was the one who mixed Ice and Fire to create Ymir. HE was the Father of Ra. HE is the Father of Izanagi and Izanami. HE is the very Universe itself to the Buddhist and their followers. HE is known now as KHAOS, but HE wasn't always this powerful and omnipotent. Before HE created this universe HE destroyed the previous one. HE was once a regular mortal just like the ones below. Mortals who evolved from monkeys and gained unusual power at the last point of their evolution before HE wiped out the universe.
Although HE had long shed HIS Mortal body, HE once went by the name of Izuku Midoriya, the ninth successor of the stockpile quirk, One For All that had never stopped growing in strength since its inception Millions of years ago.
However a stockpile ability doesn't have the tools to grant immortality, omnipotence and creation. In order to know about the cause of HIS strength, you must be aware of the war he arose from.
Although it had 2 parts, it was acknowledged in total as The Paranormal Liberation War. The people fought for the right to use their peculiar abilities as they deemed fit, regardless of the laws placed to inhibit them. "It was just a new piece of their evolution!" they reasoned. You cannot ask a major world populace to not use a limb they all possessed. The laws that used to exist simply covered wounds and problems -never really healing them-, till the pain became too much to bear and the people revolted.
In the war HE fought One For All's counter and almost fell if not for HIS will. All For One as the name describes, is a power to steal the power of others, and in a world where everyone possessed one, it was not difficult to climb to the peak of evil "civilization". All For One planned to steal the one power that evaded and combated him for a century and a half, in order to finally become the true ruler of the world. He came so very close.
While possessing the body of the Seventh Holder's grandson, he used the boy's hatred to overpower One For All's will, and so One For All had to rely on Midoriya's willpower. One For All and All For One have 1 drawback that they both possess, and 1 drawback that separates them. The shared drawback is on the holder's physical body. The body must be strong enough to withstand the physical power the quirks contain to be used effectively. However that is where the similarity ends.
One For All's second drawback is that it can only contain and apply as much power as it has stockpiled. It could never APPLY more power that it has stockpiled and never CONTAIN less energy than it had stockpiled, to be exact. The longer or more it was used the stronger it got, but it could never break those particular rules of physics.
All For One's second drawback is that the will of its holder must be stronger than the will of its victims to take their abilities by force. If the holder's will is weaker, the quirk and all the quirks it contains will migrate into its victim's body, leaving the current holder.
Unfortunately for All For One, both quirks and their "vestiges" had underestimated Midoriya's will. Years of being quirkless while still holding onto the dream of heroics had built the child's will up to immeasurably levels.
Tenko Shimura, the second "All For One", and Tomura Shigaraki, the first, did not stand a chance.
The All For One quirk transferred to the ninth Holder of One For All, taking all of its quirks with it. This did not happen without consequence as All For One fed off One For All's never reducing energy, and began to manifest in the outside world. Tenko Shimura's "Decay" quirk was intrinsically mixed with the All For One quirk due to the Mad Doctor's work, so the All For One quirk stole the quirks of every living or dead being on the planet and simultaneously decayed them.
Tomura Shigaraki's plan was to steal One For All and use Tenko Shimura's consciousness and hatred to keep the quirks separate. This would have worked because both of the "vestiges" in the All For One quirk were still physically alive in the mortal plain. The One For All quirk clearly did not have that luxury of a failsafe causing the malfunction. After the complete destruction of the Earth, the All For One Decay aspect continued to remain active and feed off One For All's seemingly limitless and now constantly growing energy. It did not stop until it had spread to the rest of the Solar System, the rest of the Milky Way, the rest of the Galaxy, the rest of the Superclusters, and eventually the rest of the ever expanding Universe. Up until there was nothing left.
When Izuku Midoriya awoke, months had passed, and the stockpile of HIS total energy had grown to immeasurable heights and HIS body did not exist in the physical form anymore. Mortal flesh could not BEGIN to handle the power HE now possessed, however it was fortunate that some of the many mortals' quirks had the ability to create ethereal bodies of some kind in some way shape or form.
It was because of those quirks that HE still existed at all, despite wiping out all matter in the universe.
In the blackness of space, HE cried. HE was now alone in the universe as there was not even rubble left to signify the existence of anything at all. For days HE wept. Saddened by the loss of all HE held dear. What even was a day anyway? The celestial body the time measurement was used for is gone. There is no earth to monitor the rotation of, but he knew it was days because of the many time quirks HE now possessed.
That's it. There is no Earth left to monitor, so HE'LL just remake it and entrust it to HIS children. After remaking the Earth much larger than it's first planet was before, HE decided it needed maintenance while HE mentally recovered from his exhaustion. For the Western Pantheons HE created HIS first children. This book shall focus on them.
Achlys, Nyx, Erebus, Gaia, Tartarus, Aether, Aion,Ananke, Chronos(not the titan, but the primordial),Eros, Hemera, Nemesis, Ourea, Pontus and Thalassa, Thanatos, and Uranus.
Each one of them had different quirks that HE had gifted to them. Achlys, HE gifted him the ability to absorb the life force of the living mortals on the planet. HE gave Gaia the quirk granting control over nature. HE gave Chronos the ability to control time itself, and HE gave Tartarus the ability to imprison all beings in his essence as a sort of prison, with a fail safe preventing him from absorbing all of his siblings intentionally.
HE tasked all of them with the mission of protecting the planet, engraving it in their brains using the same quirk that made the Nomu of HIS generation.
And then HE rested. For seven Millenia HE slept.
When HE awoke, HE wasn't expecting the mess currently in front of him, but HE really shouldn't have been surprised.