One of the Xilien's many tools of destruction, the creature Zilla was first dispatched in Sydney, Australia, as part of a worldwide assault that included Rodan, Anguirus, King Caesar, Kamacuras, Ebirah and Kumonga. The beast wreaked havoc on its surroundings, destroying vehicles in its powerful jaws and devouring those unfortunate enough to get in the way. Just as suddenly as the monsters appeared, though, the creatures all vanished in a flash of light. Finally revealing them self to humanity, the Xilien's use the disappearance of the kaiju as a sign of loyalty to the human race. The alien invaders move to phase two of their plan, warning the inhabitants of earth about an oncoming star, called Gorath, that humanity must focus its firepower on in order to destroy. Before the scheme can fully go into effect, though, the Xilien's true intent is discovered, and it's revealed that they were the ones controlling the monsters during the earlier worldwide assault. The collapse of their old plan causes a power struggle amongst the Xilien, leaving their former leader dead and a new plan to invade the Earth in his place. Uniting their fleet of ships with the controlled monsters, the Xilien start a full-scale war against Earth. Out of options, the Gotengo was forced to release Godzilla from his artic confinement so it could do battle with the invaders.

Seeking a rematch with the airborne warship, Godzilla chases after the Gotengo, arriving in Sydney. In response, the Xilien dispatch Zilla to defeat the King of the Monsters. Zilla charges at his enemy, lunging at his opponent just as Godzilla turns and bats the creature away with his tail, sending Zilla colliding into the Sydney Opera House. Not wasting the opportunity, Godzilla powers his ray and decimates what's left of the Opera House along with Zilla.