The character is usually depicted as a supervillain and demonic god of evil who is best known as an enemy of Hercules and Thor, and as the main antagonist of Chaos War.

[1] According to the Official Handbook of the Marvel Universe's profile on Mikaboshi, billions of years ago, after the Demogorge had purged the degenerated Elder Gods, the Shinto gods Izanagi (a seventh-generational deity of the ancient Amatsu-Kami pantheon) and Izanami (an aspect of the Elder Goddess of Earth, Gaea) ventured into a formless world (Earth) that was dominated by a dark, primordial void where the ancient force of nature known as Amatsu-Mikaboshi existed and reigned alone.

The divine couple began to populate the world with living creatures as well as lesser Amatsu-Kami who later came to be worshipped as gods by the inhabitants of Japan, which enraged Mikaboshi.

His attempts to topple the fledgling Amatsu-Kami pantheon were foiled, and Mikaboshi was forced to descend to Yomi, which Izanagi designated as the netherworld of the Japanese, where he remained for centuries.

[4] He is the delegate offered by the Gods of the East, led by Izanagi-no-Mikoto, who say it is an opportunity for him to redeem himself (though Hercules later suggests that they probably just wanted him off their hands and when he first sees Mikaboshi he attacks him).

Mikaboshi vows revenge on the Olympians, free of the Kami's seals and unaware he is being observed through an enchanted scrying pool by a smiling Athena, Goddess of Wisdom, who claimed her plans had gone even better than had been expected.

Thrann, Saint of Science, tells them that the First Mover, who gave the Marvel 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.

[8] Mikaboshi next destroys Nightmare and claims the Dream Lord's powers, thus disabling most of Earth's mortal defenders and trapping them in sleep.

His power is of such extent that he can control numerous minor demons, as well as animating and manipulating corpses en masse at will; moreover, even the Kami themselves appear wary and fearful of Mikaboshi whom they consider their primal foe, especially as he himself has slaughtered much of their pantheon.

Mikaboshi possesses an extremely high intellect rivaling that of genius-level, and is an accomplished strategist, though his preferred tactic is simply overwhelming opponents with the sheer number of his demonic foot-soldiers.

After seizing control over thousands of alien deities of the Skrulls, and using them to tear through worlds and realities to eliminate the gods of countless other extraterrestrial civilizations, such as the gods of the Shi'ar and the gods of Zenn-La, Mikaboshi was able to gather enough power to shed his "Terran form" and emerge as the Chaos King, the primal embodiment of nothingness and primordial chaos that served as a natural opposing power to both Eternity and Death, and a threat to the entire Marvel Multiverse, and all its powered mortals, living or dead, abstract conceptual beings, cosmic entities and lesser divinities.