It started with the Castle Bravo test in 1945. Or at least, that is how humanity thought it started. Somewhere in Mexico, citizens fled in terror as an Kaiju that did not resemble Godzilla whatsoever was now terrorizing their little city, claws tearing apart buildings with ease as its odd wings let it glide seamlessly through the starry night sky. Across the ocean, an titanic ruler opened his yellow eyes, peering deep into the oceanic surroundings as he started swimming, the large dorsal fins on the Kaiju's back scaring away sharks and octopi alike as the young Godzilla remembered how he had been mutated while still in a Godzillasaurus egg, with him taking longer to hatch thanks to a different nuclear test. The soldiers had tossed the large black and grey orb into the waters, deeming it charred from their bomb. How wrong they had been, and he planned to prove it by tearing their cities apart, just like Gigan was. But the second Godzilla did not plan on sharing that glory with anyone, least of all an overgrown chicken. As the Terrorbird Kaiju smashed apart another building, he heard fast paced swimming and turned around to see an lizard, similar in size to him, rising out of the water. The King of the Monsters had returned, and he did not look happy to see Gigan messing with territory that had been it's in ancient times, back when Godzillasaurus were as common as T-Rexes. The reptilian Kaiju ran forward while the Terrorbird flew at its foe,slashing at its foe's chest, drawing a wound and a roar from Godzilla, who grabbed Gigan's claw, hissing while the less imposing Kaiju tried to back away. The dorsal fins began to glow as atomic energy built in the throat of the Kaiju Monarch before Atomic Breath seared off Gigan's entire head in a single burst while Godzilla tore both fleshy claws away, biting down on them to consume the radiation within. The terrified denizens of the Mexican city all ran for their lives, even as Godzilla left back for the ocean to cool down from the slight internal heating it got from devouring the claws of Gigan.