Between Hawaii and the Mariana Islands a large, grotesque species of crab dwelled. Called daldorfia horrida, or rubble crab, the species displayed uneven and eroded features. Its surface was covered with tubercles and pits, giving it a rough, bumpy exterior. The crustacean also had large pincers with molariform teeth to help its grip.
In 1970, though, nearby Selgio Island was invaded by an extraterrestrial presence. When the unmanned Helios-7 crashed into the waters, a Space Amoeba pursued the seas. Its first victim was a kisslip cuttlefish, transforming the marine animal into Gezora. Now a giant monster, the mammoth cuttlefish stalked the land and sea of the island. Eventually, though, the natives and visitors of the island gained the upper hand. Badly burning Gezora, the monster cuttlefish collapsed in the sea. Its body drifted to the bottom, marking its final resting place. From Gezora's corpse, though, the Space Amoeba crept out. Looking for another life form to posses and transform, it searched the waters.
In its search, the alien came across the daldorfia horrida. Possessing the crab, the crustacean transformed into the giant Ganimes. Controlled and powered by the malevolent intelligence of the Amoeba, the giant crab went on the attack. In a geyser of water, knocking over an unlucky escaping raft, Ganimes bellowed a cry at the humans. The people on the island, though, had equipped themselves with weapons from an abandoned ammunition depot. Using World War II era weapons, Ganimes was lit up with machine gun fire. The creature's shell was too strong, though, as Ganimes was left unharmed.
Trying to finish the job that Gezora left undone, the monstrous animal wadded inland. Realizing the danger, the islanders dispersed into the jungle. The monstrous daldorfia horrida was too fast, though. Using its powerful pincers, it smashed vegetation in its way and managed to clip two natives. The attack sent them flying into the sky, crashing with a sickening thud a distance away. Confronted by the monster, the humans went on the offensive. Igniting miniature explosives, the natives shelled Ganimes, destroying the ground around him. As the humans split up, the giant crab decided to chase two of them. This was a mistake. One of the humans, a photographer, used his rifle to aim for Ganimes' eye. The shot landed its target, leaving the rubble crab blind in its right eye. As red blood oozed from its socket, the beast paused momentarily. Ripping up the jungle with its pincers, though, the monster once more pursued the two humans. Led to a treacherous cliff, the photographer took aim and destroyed Ganimes' other eye. Now totally blind, the creature swung wildly with its pincers. Foaming at the mouth, the daldorfia horrida lost its footing and fell off the cliff. Slamming into the ground far below, the crab's thick exterior protected it. However, the beast happened to have landed near the abandoned ammunition depot. Seizing the opportunity, the photographer used his rifle to strike some of the gasoline tanks near the depot. Causing a fire, the tanks quickly ignited, triggering the huge cache of explosives. The resulting explosion tore Ganimes' body apart, leaving smoldering bits of flesh. These pieces were sent clear across the island. The Space Amoeba, though, was far from dead, even if its host had been destroyed. In fact, the explosion split up the alien being, who sought three hosts this time. Crawling from the open carcass, it assimilated a human, a mata mata turtle and another daldorfia horrida. This gave birth to a second Ganimes.
Using the human, the Space Amoeba made their intent clear: they planned to conquer the Earth. To realize this plan, they intended to control more humans and mutate more monsters. What the invading aliens hadn't anticipated, though, was humanity discovering their weakness. Remembering that both bats and dolphins had chased away Gezora, it was realized that the being shied away from ultrasonic waves. Trapping a cave full of bats, both the turtle monster Kamoebas and Ganimes converged on the humans' location. The monsters' partnership was soon dissolved, though, when the horde of bats besieged the giants. The ultrasonic waves created from their cackling cries broke the Amoeba's hold. Sending the two monsters into a mindless rage, they attacked each other. Ganimes was the first to strike, clubbing the giant mata mata turtle with its pincers. Kamoebas retaliated, using its long neck to reach below the giant crab and throw it into the air. Ganimes then landed on the turtle's back, who used the force of its body to launch the crab to the ground.
The battle had just begun, though. Using its claws and spitting its foam, Ganimes attacked relentlessly. Despite its efforts, though, Kamoebas was able to hold its ground. Using its claws, Ganimes kicked up boulders, sending them cascading down at the monstrous turtle. Kamoebas' shell protected it, though. The turning point in the battle occurred when the giant daldorfia horrida caught the mata mata turtle's neck in its pincer. Dragging its prey, they both proceeded to the lip of the mountain. So caught up were the monsters in their war, though, that they didn't notice the volcano that they fought on. Using its body, Ganimes tossed Kamoebas, only for the turtle to grab a pincer with its teeth. As both monsters struggled, they both fell into the volcano. An eruption was quickly triggered, killing the monsters and the Amoeba beings that laid within.