200,000 years ago-
A meteor destroys a planet, wiping out most of its inhabitants. The surviving inhabitants turn themselves into mostly machine cyborgs dubbed Bio-Mecha. The destruction of most of their planet had warped their minds, and the now nihilistic Bio-Mecha chose to create creatures that would act as grim reapers to bring planets to their inevitable destruction. So they created, using their own DNA, an entire race of giant silver bat-like creatures which would be extremely ravenous. The creatures would go on to destroy countless worlds.
11,000 years ago-
The civilization of Atlantis is founded, and quickly becomes a very impressive civilization.
10,000 years ago-
The Atlantians discover the life energy of the earth, AKA Mana, and how to use it to create their own life.
9,500 years ago-
The Bio-Mechas engage in a war with the Virasian aliens, a race of sapient squids who had the ability to combine into a giant monster named after their sun, VIRAS. Viras battles one of the Bio-Mecha's bat creatures, which they called Reapers, and the two kill each other. The Bio-Mecha eventually won the war, but the Virasians managed to escape. Following the war, the corpse of the Reaper that fought Viras lands on earth, where it is discovered by the atlanteans.
5,000 years ago-
The subterranean snake monsters GARASHARP begin attacking Atlantis. In response, the atlanteans clone the reaper using Mana, creating their own nearly identical creatures, whose only difference from the reaper was that they were black, and the Atlantians named them GYAOS. The Gyaos defeat the Garasharp, but soon turn on the Atlantians once their food supply runs dry. The Atlantians create another monster called JIGER to attempt to stop the Gyaos, but it ends up going rogue too. Finally, multiple giant turtles are created called GAMERA, which are connected to Magatama. While only 2 Gameras survive, the evil monsters are driven away.
4,993 years ago-
The last two Gameras, a male and a female, end up falling in love due to them bonding over being the last of their kind, and become mates.
4,990 years ago-
The Gyaos and Jiger return, along with a massive Garasharp Matriarch. The last two Gameras engage in a final battle with them. During the battle, the female Gamera, GAMMERA, fights a Super Gyaos alone, eventually reaching the arctic. While the Gyaos is killed, the battle causes an avalanche that causes Gammera to be encased in ice. Eventually, Gamera destroys the entire Atlantean continent, realizing the world would never know peace as long as the Atlantians kept consuming Mana. Survivors of the battle memorialize it atop a dormant Gamera, and lock the barely alive Jiger in the nearby Devil's island with an artifact called the devil's whistle.
3,000 years ago-
The monster BARUGON first awakens and menaces villages in New Guinea before being killed by hunters. Barugon was a previous attempt at creating life by the Atlantians before Garasharp appeared, but had been deemed insufficient and let out into the wild. From there on, Barugon reincarnates in an egg every thousand years to menace New Guinea.
1,000 years ago-
Silicon based lifeforms called LEGION evolve and begin terraforming planets into ones they could live on, destroying countless species in the process.
1945-
A japanese soldier named Ishiro discovers Barugon's egg, mistaking it for an opal and placing it in the valley of rainbows, a vast complex of caves in New Guinea's dense rainforests.
1964-
The Bio Mecha and their Reapers attack the planet Terra, wiping out most of its population.
1965-
A jet fighter carrying a nuclear bomb crashes in the arctic, and the explosion frees Gammera from her icy imprisonment. Searching for fire to feed on, she attacks a geothermal power plant. Man-made weapons are powerless against her, but the Japanese government manages to defeat her by trapping her in a rocket and sending her to space.
1966-
Gammera's rocket crashes into a meteor, freeing the giant turtle, who returns to earth and destroys Ogochi dam. Meanwhile, an expedition is mounted to retrieve Barugon's egg, which was still thought to be an opal. However, two of the men are betrayed by the treacherous Onodera, who takes the egg back to Tokyo. Once Barugon hatches, its exposure to infrared rays causes it to grow huge. It rampages, and Gammera fights it, being frozen in the process. However, after she thaws out, Gammera defeats Barugon.
1967-
A single Super Gyaos is reawakened inside a volcano, and after destroying a helicopter containing several scientists, attacks a small village protesting road construction. Gammera appears and saves a child about to be eaten by Gyaos, and the two have a brief scuffle before Gyaos flies away. After healing from her injuries sustained in the battle, Gammera and Gyaos fight again, Gammera losing but managing to tear off Gyaos's leg. After a failed attempt by the humans to defeat Gyaos, Gammera returns and kills him by dropping him into a volcano.
1968-
A virasian ship sent to colonize earth is destroyed by Gammera, who had sensed them approaching. Shortly afterwards, two genius boy scouts are captured by another virasian ship, and after learning of Gammera through reading their minds, use a mind control device to put her under their control. A mind controlled Gammera destroys Tokyo once again, but luckily the two boy scouts are able to reverse the controls and make Gammera attack the aliens. Afterwards, the kids escape, and the virasians merge into Viras. After a brief fight, Gammera defeats and kills Viras.
1969-
A terran spaceship crashes on earth, and two young boys accidentally activate it. Gammera notices it and tries to save the boys, but the ship outspeeds her and lands. When the boys exit, they are attacked by the only Reaper still on the planet, which the boys call SPACE GYAOS. The terran's guardian monster GUIRON then appears and kills the Space Gyaos. The boys then encounter the last 2 terrans, who pretend to be friendly but intend to eat them. Meanwhile, Gammera appears on Terra and battles Guiron, but loses. After the boys escape, Gammera recovers and manages to defeat Guiron, putting the spaceship back together afterwards, and allowing the kids to return home.
1970-
The devil's whistle is removed in order to transport it to Expo 70, but this ends up freeing Jiger. Jiger and Gammera fight, with their battle eventually reaching Tokyo, where Gammera is impregnated by Jiger's parasitic larva, causing her to become dormant. Jiger hunts for the statue, and the humans discover the larva within Gammera's body. This is when they also discover Gammera's gender. After two young boys kill Jiger's larva, Gammera reawakens and battles Jiger, ultimately defeating it by throwing the statue through its brain.
1971-
The alien shark monster ZIGRA attacks a moonbase, and then arrives on earth to use humanity as food. He fights Gammera, at first knocking her into slumber with his stasis ray, but once she reawakens she defeats Zigra by setting him alight with her high plasma fireball, then flying off.
1972-
While flying over the ocean, Gammera discovers her slumbering mate. She lands on top of him, and after being unable to wake him up, they engage in telepathic conversation. Gammera tells Gamera everything she had been through since they had last seen each other, and the two end up deciding to have a child.
1973-
Gammera lays her egg on a rocky atoll, but then senses a group of Gyaos attacking the fishing village of Shima. Gammera heads to the village to protect it, arriving by sea. However, while she is able to kill one of the Gyaos, Gammera gets overwhelmed by their numbers, and ultimately blows herself up to stop them. Following this, strange pearls are discovered around the village, which came from Gammera. The Japanese government forms a task force called the Science Defense Academy to detect any more monsters, while an undersea reptile begins feeding on the Gyaos corpses…
1974-
Shima becomes a popular tourist attraction thanks to the pearls, boosting Shima's economy greatly. The Science Defense Academy also begins collecting the pearls.
1980-
A movie is made to commemorate Gammera's sacrifice for mankind, simply titled, "Super monster." The movie used footage collected from all of Gammera's fights (minus her final battle with the Gyaos) to tell its own story involving Spacewomen and a very clear ripoff of a Star Destroyer. Made with a very small budget, the movie ended up flopping at the box office.
1995-
A group of juvenile Gyaos emerge and begin feasting on humans. In response, Gamera awakens from his slumber and begins hunting the Gyaos. The Science Defense Academy also aids Gamera in these battles. Eventually, Gamera fights a Super Gyaos in Tokyo, defeating it before returning to sea. During this time, humanity learns of Gamera and Gyaos's origin.
1996-
The Legion arrive on earth and create a plant to make soldiers. Gamera arrives to destroy the plant, however, he is overwhelmed at first, and when he goes to destroy another plant, he encounters the colossal MOTHER LEGION. While Gamera is able to defeat her, it takes him using a majority of earth's mana to fire a mana blast from his plastron.
1997-
Biologist Greta Karbone, who had disappeared after faking her death in 1990, steals a sample of the DNA of the Super Gyaos that attacked in 1995, and uses it to create her own personal monster army. However, her greatest creation, MORPHOS, ends up taking control of her mind. Morphos begins destroying Paris after shapeshifting into Gamera, but the real Gamera soon appears to stop him. The two kaiju fight, with the real Gamera eventually coming out on top. Karbone is killed in the midst of the battle.
1999-
Gamera fights a failed Gyaos prototype called IRIS, and while he does defeat it, it costs him his arm. A swarm of Hyper Gyaos then descends on Gamera, with the Guardian of the Universe fighting them alongside the Science Defense Academy. By some miracle, the Hyper Gyaos are defeated, but Gamera limps back into the ocean afterwards, being presumed dead by the world.
2000-
The Bio-Mecha appear on earth and begin attacking it, the Science Defense Academy rushing to stop them. After several battles with the Bio-Mecha, the Science academy fight a giant NEO GYAOS and several Space Gyaos. As one of the jets is about to be destroyed, a very much alive and well Gamera appears and saves them. Gamera then destroys all of the Gyaos and then flies to the Bio-Mecha's mothership, destroying it alongside the jet fighter he saved. With the Bio-Mechas finally destroyed, Gamera departs.
2006-
ZEDUS, the aquatic reptile that had mutated by feasting on the Gyaos corpses from 1973, begins killing humans at sea. At the same time, a young boy named Toru discovers the egg that had been laid by Gammera, which hatches. Toru names the baby TOTO, and takes it home with him. Toto begins growing rapidly, as Zedus begins attacking Shima. Toto fights him, but barely manages to survive. Toto is then brought to a facility where he is hooked up to a machine that feeds him a liquid version of the red pearls. Zedus attacks again, and Toru fights him, being overpowered until Toru gives him the stone he found with his egg. Using this powerup, Toto is able to defeat Zedus. Gamera then arrives, and at Toru's insistence, Toto flies away with him.