It would seem the return of the formerly believed-to-be-dead Hercules would herald joy for the world, but instead he brings grave warning to the heroes of the world. Brought back by the Prince of Power; Amadeus Cho, Hercules, with Thor and Cho by his side, lead an army of heroes to face the looming multiversal threat of the Chaos King who had and was attacking, killing and consuming the power of all the gods and god-like beings from all pantheons and dimensions across the multiverse in an effort to consume and absorb the entirety of the multiverse to return it to it's original state; pure chaos. When Hercules lead the heroes for their initial attack on him, the Chaos King incapacitated the heroes and all the citizens of the world by using Nightmare's dreampower, leaving no one but gods and other god-like beings to oppose him. Hercules and Thor, with the help of Amadeus Cho, brought together a new incarnation of Herc's former team, the God Squad to defend reality and devise a way to stop the Chaos King.
The Chaos King solidified his hold on the universe with more gods of the different pantheons as they fall to his power. Soon after gaining control of all the various realms/aspects fo the underworld, he released the lost souls of countless dead people including the dead members of Alpha Flight, Avengers, and the X-men. With the influence of death removed from the universe, dead heroes and villains alike return to the land of the living, with many choosing to fight either for or against the Chaos King. In the end, it all comes back to the Chaos King as he now fights the only one left to stand in his way; the new, All-Father Hercules. The two adversaries battle savagely on a scale that dwarfs planets. With space and time crumbling as there fight rages, Amadeus instructs Hercules to punch the Chaos King into a pocket universe (the Continuum) where he is now alone as the be-all, end-all which made him believe he had won. The multiverse, however, had been laid waste by the Chaos King's war upon it and was now in shambles. Realizing this, Hercules, in what would be his last act as the all-powerful God of Gods, used his omnipotence to repair and restore the multiverse to it's proper state. Unfortunately, the act of doing this was so incredibley difficult it required every bit of godly power and might he possessed, leaving him fully and completely mortal afterward.
The Greek demigod Hercules had been presumed dead, but the moment Amadeus Cho brought him back and made him an all-father (the greatest of a pantheon of gods), he knew immediately that Amatsu-Mikaboshi (The Chaos King) was about to launch his attempt to destroy all of creation.
Emboldened by the destruction of Asgard at the end of the Dark Reign, the Chaos King hoped to destroy all of the gods and then the defenseless multiverse. He started by finding and murdering Nightmare, the Lord of Dreams, this gave him the power to destroy any mortal mind he touched, which he used against the heroes that Hercules assembled to attack him, plunging them into waking comas.
Amatsu-Mikaboshi then attacked the afterlife. To defend himself, Hades (Pluto) released the dead to fight for him, resurrecting dead gods and heroes including Ares, Genis-Vell, Deathcry, Doctor Druid, Zeus, Banshee, Moira MacTaggert, Swordsman, Thunderbird, Vision, and Yellowjacket. Despite this, the Chaos King triumphed.
In response, Hercules assembled a new The God Squad consisting of Amadeus Cho, Hellstorm, Galactus, Sersi, Silver Surfer, Thor, Venus, and himself. With the help of the wisdom of the traitorous Athena, the Chaos King outwitted and defeated them all. After conferring with Gaea, Amadeus Cho realized that there was no way for them to defeat the Chaos King. Desperate, Hercules allowed Pele, the goddess of fire, to turn him to ashes so he could remake himself as a god able to tap into the fullness of his newfound power. As Hercules went to face off the Chaos King, Amadeus Cho convinced Galactus to open a portal to an empty multiverse the goddess Hera had created to replace the real one. The Chaos King was beating Hercules and all of his friends, but Amadeus Cho couldn't decide who of the millions of people on Earth he should save in the limited time that remained. In a flash of inspiration, he had Herules knock the Chaos King into the empty continuum, which he immediately destroyed, thinking it to be the real multiverse. With the Chaos King defeated, Hercules spent every last bit of all-father powers to restore the multiverse as it had been before the Chaos War begun. When he was done, several of the dead who'd been released by Pluto remained restored to life, including Yellowjacket, Swordsman and several members of Alpha Flight.
Soon after this event, Bruce Banner confronted Hercules and demanded that he fix the Hulks' problems as a reward for what they had done during the Chaos War. When Hercules revealed that he no longer possessed the All-Father's powers, Banner turned into the Hulk, stormed Olympus and challenged Zeus to a battle. The Hulk was defeated and chained to the mountain, where vultures devoured his body for days. Hercules and the rest of the Hulk family saved him. Zeus decided that Hulk had learned to respect him and he wouldn't pursue him any longer - such an auto-destructive persona as him will bring the best punishment upon himself.