Chaos King's History
The entity known as Amatsu-Mikaboshi originated as an aspect of Oblivion, the cosmic entity embodying the void that existed before the universe began. An incarnation of the primordial darkness and chaos that existed before the universe, the Chaos King exists as a dark counterpart to Eternity, whose genesis stripped the Chaos King of much of its power and led to it being integrated into the Shinto cosmology as "Amatsu-Mikaboshi".
According to Shinto cosmology, Amatsu-Mikaboshi ruled over the Earth when it was nothing more than a formless void of primordial darkness, until the elder god known as Gaea - in the form of Izanami - and a young Amatsu-Kami called Izanagi created the islands of Japan from the Void using the divine Jeweled Spear, enraging the dark god. The dark entity declared war on Izanami, Izanagi, and their divine children the Amatsu-Kami - who later came to be worshipped as gods by the humans of Japan; but was ultimately imprisoned in the the netherworld of Yomi, where he remained for centuries - accruing an army of Oni, Shinma demons, and other monsters.
Warriors Three:
The Warriors Three were put on trial for accidentally killing a giant who had shape-shifted into an aquatic beast. As punishment they were sentenced to retrieve several difficult items from various pantheons and return them to the father of the dead giant. This included the sword Grasscutter from Yomi guarded by Mikaboshi.
Creation of the Ebon Samurai:
When Japanese police officer Kioshi Keishicho was killed by the Silver Samurai and ended up in Yomi, Mikaboshi approached him and offered to resurrect Kioshi so he could seek revenge. When Kioshi accepted, Mikaboshi bonded him to a shinma demon that manifested as a black suit of samurai armor and a katana capable of cutting through almost anything.
Ares: God of War:
Taking advantage of the chaos left by the fall of Asgard and the Norse pantheon, Mikaboshi planned to extend his influence by capturing Olympus and crushing the Olympian gods. With the Olympians defeated, Mikaboshi hoped to compel all the other pantheons into surrendering. To this end, Mikaboshi laid siege to Olympus, which was very close to succeeding. Ares, still bitter about the treatment he received from the other Olympians, refused to raise a finger to help them. Desperate for his aid and wishing to goad Ares into action, Zeus had Alexander kidnapped and brought to Olympus where he was placed under the care of Achilles and his Myrmidons.
With Mikaboshi in utter control of the battle, Hermes went to Earth to fetch an enraged Ares in an attempt to get him to speak with Zeus, but Ares' only concern was his son. Relenting, Hermes transported them both to Achilles' stronghold where they kept Alexander, only to find the fortress destroyed and Alexander missing.
While Achilles was away, Mikaboshi's forces managed to destroy the Myrmidon fortress and steal Alexander away to his own stronghold in the eastern lands. Mikaboshi slowly began to warp Alexander's mind in an attempt to turn him against his father by revealing the brutal history and patricides committed by the Greek gods. Mikaboshi hoped to turn Alex into the new god of war, one that could be used against the Greek gods and, more importantly, Ares himself.
Finding out his son was in the hands of Olympus' enemies, a furious Ares begrudgingly agreed to join in the fighting, but only to rescue his son. During the battle, Zeus was on the brink of death and used his remaining power to break the hold Mikaboshi had over Alexander. Alexander used the Grasscutter sword against Mikaboshi and ended the battle.[4] Mikaboshi was then returned to the Japanese land of the dead defeated.
Athena of the Olympian Pantheon called a meeting of the Pantheons in San Francisco to assemble a team of Gods from Earth, known as the "God Squad". Mikaboshi was chosen by the pantheons of the east along with Hercules, Snowbird, Tecumotzin, and Atum, the God Eater to battle and defeat the Skrull Gods Kly'Bn and Sl'gur't. In route to Skrull space through the dream realm, they battled Nightmare. Mikaboshi was key in winning the battle by being able to make duplicates of himself.
Upon arriving in Skrull space, the God Squad had to battle their way through conquered pantheons of gods on the way to Kly'Bn and Sl'Gurt’s thrones. Mikaboshi attacked Sl'gur't after she destroyed Atum, and both took shape of the same creatures during battle, eventually taking the form of each other. Mikaboshi killed Sl'gur't before being left by Hercules, Snowbird, and Amadeus Cho who thought Mikaboshi was killed, thus leaving Mikaboshi to take command of the conquered pantheons
Chaos War:
Athena had been preparing herself for many years in order to fight the great struggle against the primordial darkness, Mikaboshi, who would soon descend upon the world, telling Amadeus Cho that Hercules' strength would be useless, but Cho's genius might bring them victory. Later, Hera had vision of Mikaboshi slaying the Shi'ar Gods, Sharra and K'ythri.
Amatsu-Mikaboshi amassed a great army of enslaved deities, though a small number of them had willingly joined him as seen with Glory. They soon attacked the Old Gods of Zenn-La, who were awaiting his attack. Thrann, the Saint of Science, had told his fellow Zenn-Lavian gods that the First Mover, who gave the Universe "orbit, organization, and order" from a void of chaos and nothingness, extrapolated the coming of the Nil Star as the herald of the End Times eons ago. Mikaboshi eventually invaded their Cosmic Plane and easily destroyed them, enslaving them to further bolster his forces. After that he began approaching Earth, while killing Impossible Man in the process.[6] He then destroyed Nightmare and claimed his powers, thus disabling most of Earth's mortal heroes by trapping them in their sleep
Hercules tried to summon Eternity so he could fight the threat, but the being refused since fighting Mikaboshi would just be him fighting himself, as Mikaboshi is the void against which he is defined; however, he assured the heroes that they would be able to defeat him. Satan and his son Daimon tried to defend Hell, but they also fall as Mikaboshi devoured the ruler and destroyed the Underworld, causing Death to flee the universe. This allowed Mikaboshi to take control of an army of dead beings
After enslaving the Olympians, he used them against the reformed God Squad, even taking down Galactus through Zeus. After Hercules was tricked into piercing the shields which concealed hidden Throne Room of the Council Elite's Celestial Axis, Mikaboshi and his army erupted from Zeus' chest launching a devastating assault on the divine realms of all of Earth's pantheons and destroying most of the gods, even the various Godheads themselves.
The Amatsu-Kami tried to confront Mikaboshi, with Amaterasu trying to defeat him as she did in the past, but they were no match as he enslaved them and used them to fight against the God Squad. Amatsu-Mikaboshi also went after the Inua, causing great fear in the Great Beasts who felt they would be next. He also gained new allies in Nekra, Grim Reaper, Miek, and Abomination, the latter fighting Doctor Strange. Mikaboshi attacked Strange from behind, awakening Zom within him, and ordered the being to go after Marlo Chandler since she held a connection to Death. He then unleashed Carrion Crow on the revived members of the X-Men, in order to get one of Destiny's diaries which could hold the key to defeat Mikaboshi
Eventually, Mikaboshi relished the slow death of his oldest enemy, Gaea, who herself was the fountainhead of creation and the one who birthed the Gods. When the God Squad went to an island in order for the universe to be recreated, Mikaboshi sent Athena to attack her brother who had recently achieved godhood, but was defeated
Hercules and the other heroes took the fight to Mikaboshi, but the being began consuming all reality into nothingness. However unbeknownst to him, during the battle Hercules punched him into the Continuum, an infinite pocket dimension that Amadeus and Galactus had created to originally be a safe place where to evacuate Earth, but was turned into Mikaboshi's eternal prison. Thinking he was still winning, Mikaboshi continued devouring everything in his path, completely unaware he had been sealed away from the main reality. Hercules later sacrificed his godhood in order to undo the damage caused by Mikaboshi and restore all of reality.