Emerging from hyperspace near Jupiter's orbit came a massive spacecraft. Piloting the vessel were the Dianii, gigantic intergalactic hunters who had followed their prey, the Korghan beast, to Earth. On Earth, the Korghan beast was known as Bagorah, the mighty bat monster. Detecting that Bagorah had been defeated by a similarly large organism, the Dianii decided to switch the target of the hunt from the giant bat to this new beast. Arriving on Earth, they found that their new prey - Godzilla - was under attack by the mechanical All-Terraintula. Deciding that a wounded animal was unworthy of being hunted, the Dianii decided to remove the mech from the picture and blasted it with their Mega-Zooka, a powerful cannon that sent the All-Terraintula down in flames.
Before the Dianii could focus their efforts on Godzilla, however, the King of the Monsters fell unconscious due to the All-Terraintula's super-tranq. Disappointed, the Dianii momentarily considered resuming their search for Bagorah before deciding to revive Godzilla to allow their apprentice to practice killing him. One of the Dianii fetched a gigantic jump-starter, zapping Godzilla's prone body with it. Though Godzilla started coming to, the Dianii kept zapping him with it, trying to rile him up. Godzilla responded by biting down on the Dianii's shoulder and tossing him into the street. Godzilla tried to blast the hunter with his atomic ray, but his internal fires were temporarily extinguished by the super-tranq. The injured Dianii began laughing at Godzilla for having lost his fire, but soon realized his mistake as Godzilla charged him and stomped his entire torso into the concrete. The other Dianii were momentarily shocked, but then laughed the loss off and soon began following Godzilla as he moved back towards Portland. When Dr. Kagaku tried to make contact with them in an attempt to warn them they were about to endanger a heavily populated area, the Dianii got annoyed with him and scared him with a mock-stomping.
One Dianii, the Bowmaster, pulled out his massive bow and arrows and unleashed them at Godzilla. Again and again he fired, until Godzilla looked like a pin cushion. Angrily, Godzilla gave chase to the alien, who quickly ran, getting Godzilla in position to be ambushed by the others. The Dianii Captain launched grappling cables that tied Godzilla's legs together, and once he hit the ground, the young Dianii tossed and covered Godzilla with an electrical net. The ensuing electrical assault barely stunned Godzilla, but he was soon attacked by the Spearmaster, who plunged his weapon into Godzilla's chest. The blow did little more than enrage Godzilla, who slammed Spearmaster to the ground and then rolled onto him, crushing the alien underneath. The young Dianii was yanked off the building he stood upon by Godzilla pulling on the cable attatched to the electric net, but before Godzilla could smash him underfoot, he was attacked by the Dianii warrior. The mighty brute tugged on Godzilla's tail before having his legs crushed and then smashed into a nearby building.
All that remained now were the Captain, the young one and Bowmaster, and the three were quickly trying to retreat back to their ship. Bowmaster instructed the young one to take the Captain to safety as he distracted Godzilla. Hitting Godzilla with one last arrow and then taking cover behind a building, Bowmaster never even saw it coming when Godzilla sent a skyscraper toppling onto him.
Now with the knowledge that the Black Hole Aliens had assumed control of their ship, the Captain and young one were helpless. As they tried to come up with a plan to regain their craft, the Captain was suddenly vaporized by a blast from the reactivated All-Terraintula. Now all alone, the young one went into a crazed rage and attacked the mechanical spider, beating it with the Captain's remaining arm. Grabbing the mech, he spun it around and let it fly at Godzilla, where the machine was crushed by the Monster King's incredible strength. When Godzilla destroyed the Dianii's ship, the young one perished in the ensuing crash and explosion.
A female Dianii, who had been left on the ship and dealt with the Black Hole Aliens, managed to escape the blast and retreat into space, the only survivor of the Dianii's expedition to Earth.