Amatsu-Mikaboshi is an embodiment of the chaotic nothingness (and an aspect of Oblivion) that existed shortly before the formation of the physical universe as we know it that appears in Marvel comics as an adversary to Hercules and many other heroes across space/time.
Appearance
At first he was seemingly little more than a generic god of evil, the Japanese equivelent of Loki or Discord - however this was all a guise by the real Mikaboshi, who was no mere demon or god but an Abstract who sought to end all things so as to return to his beloved chaos.
He has appeared in Hercules, the Ares mini-series and Secret Invasion - acting as an antagonist in almost every appearance he has appeared in, furthering his guise as a "god of evil".
Mikaboshi's true form.
Amatsu-Mikaboshi would also play a major role as the primary antagonist of the "Chaos War" event - in which he enslaved pantheons of alien deities and demons with the intent of destroying the universe, returning it to an endless sea of chaos and nothingness: it was during this event that he shed his guise as a "god of evil" so as to finally reveal his true power to multiple pantheons of gods, since he was no longer holding back he quickly changed from a manipulative entity into an outright destroyer as he quickened his apocalyptic plan to erase the ordered universe and give birth to an endless sea of chaos.