It has been two years since the ancient gods had attempted to exterminate the human race for their treatment of the Earth. The gods were defeated, and the human was saved by the man-made, hybrid kaiju Chimera. With the gods no longer capable of challenging them, interdimensional beings known as the Dark Ones have returned to destroy the Earth itself. Led by the titan Cronus, the Dark Ones unleash numerous monsters, demons, and giants from the realm of myth onto the planet with the directive to destroy all forms of life. Realizing that the monsters under his command may not be capable of defeating the hybrid, Cronus searches parallel Earths to find a monster who is strong enough to challenge Chimera. After scouring countless Earths, Cronus finds Atomic Rex. With his vast powers, Cronus sends Atomic Rex to Chimera's Earth and sets the monster loose. The few gods that remain alive after the war with humans, discover Cronus's intentions. The gods reluctantly ally themselves with humans and Chimera in an attempt to save the planet. Chimera and Atomic Rex will fight their way through the gods and monster of myth as they both head to the greatest challenge either one of them has ever faced in each other.