Monster Island

Pushed-up from the ocean floor by volcanic vents, the Nullius Ager archipelago was formed of igneous rock approximately 1,800,000 years ago. Archeological evidence suggests a rather prophetic history of exotic flora and fauna. Fossil records have uncovered the complete exoskeleton of an ancient Red Kamacuras, and wing sections of a Kaiju posthumously named "Soran", among many other finds. Further archeological studies however, have been hampered by the present inhabitants.
Stories from Japanese and Chinese legends tell of a chain of islands inhabited by monsters and demons, and ruled over by gods of the earth, sea, and sky. Kept away by legend and folklore, sailors stayed clear of the area and warned others to do the same. It wasn't until 1839 that western explorers reached them, and made an extensive, if not perilous, study of the environment. Accounts of those who survived expeditions revealed to the world the first modern records of superfauna.
The islands are fixed in a semi-circle, with the two largest sitting opposite each other east-to-west. Smaller islands of various size and shape complete the ring.
The largest and main island is called Ogasawara, located on the eastern rim. This island features one of the twin volcanic peaks, Fratre in Dormit, in the Nullius Ager chain, though it has remained dormant for the past 9,500 years. Ogasawara also features the widest variety of flora, with species of flowers and trees that exist nowhere else in the world. However, efforts have been taken to ensure that the Vampire and Man-Eater Plants do not propagate outside the containment zone. The most striking feature of the island is the 102-meter wide waterfall, the Tremulo Domina, which has a spectacular 80-meter vertical drop.
It's slightly taller sibling, Adona, sits across from it on the western rim. Centered on it is likewise the opposing volcano, Fratre in Ardet. Unlike its twin however, its lava flow has remained steady for its entire recorded history. At the foot of the mountain lies the vast lake of magma, Putei Flamma, famous for providing the orange glow that radiates over the island at night. The majority of Adona is rocky and barren, most of its flora growing along the coast.
The several smaller islands that complete the ring are referred to as the Northern and Southern Scattered Islands, and given numerical designations. They're generally heavily forested, with hot springs and deep caverns, some of which bottom out in rivers of lava. There exist several examples of plant life and Tier 3 Kaiju that have speciated, Red Kamacuras on the Southern Scattered islands, and Green on the Northern.
Many mysteries do still persist as to the history of Nullius Ager. Several outcroppings on the northern tip of Ogasawara have led scientists to believe it was once a part of the main island, but something struck from above, shattering the portion into bits. No evidence has yet been found as to what could have been the cause. The biggest mystery however, is why Kaiju of all tiers seem drawn to it.
Nestled high up on Fratre in Ardet, is a cavern that connects the main vent horizontally to the eastern slope. Rodan inhabits the cavity, which looks out over the Putei Flamma, he appears to nourish himself on the heat source, and use the position as a vantage point to oversee the entire island chain. He has shown to be extremely vigilant, and particularly aggressive with the insect Kaiju for reasons unclear. One incident however, has left Kaijuologists baffled: In a situation where Kumonga threatened the adolescent Godzilla, Rodan flew across to the opposite side of Ogasawara, and drove the spider away.
Due to Rodan's temperament, most of the larger Kaiju choose to live on Ogasawara. Baragon, Gorosaurus, and Varan are a few of the regular residents, coexisting at times tenuously, and even amusingly. Others, like Kamoebas, Gazora, Titanosaurus, and infrequently Manda, occupy the waters in and around the archipelago.
Anguirus, in a similar role to Rodan on Adona, acts a type of "sheriff" for Ogasawara, going out of his way to keep the peace between his fellow denizens. In one incident, chasing Gazora back into the water after it had attacked Godzilla Jr.. Why exactly both Rodan and Anguirus exhibit such protectiveness over the young Kaiju is still unknown. Though it is theorized that it is out of loyalty to Godzilla.
When Godzilla is present on Ogasawara, the other Kaiju cede whichever portion of the island he is on, either out of fear or deference, and avoid him. Anguirus is the only one who will enter Godzilla's proximity, and has so far remained unharmed for doing so.
The efforts of the EDF to relocate wayward Kaiju to Nullius Ager have been largely successful, though containment methods have met with mixed results. Non-aggressive or rarely seen Kaiju, such as Gorgo, Sanda, and Mothra are left alone, to avoid conflict with more belligerent monsters, and overcrowding.
The monitoring station located in the Northern Scattered Islands, also serves as the main research center, and hub for Kaijuologists around the world. The Kaiju Research Institute was built in 1987, founded by a woman whom many consider the pioneer of modern Kaijuology, Dr. Quinn Darien. Sailing the world for nearly a decade with her research team aboard the Calico, she became the foremost subject matter expert on Kaiju psychology, biology, and historicity. Her memoirs, "Age of Monsters", published in 1996, chronicled her years of tracking and observing them, becoming one of the primary works of Kaiju literature, beside Steve Martin's seminal book, "This is Tokyo".
Today, the Nullius Ager archipelago, informally, and partially inaccurately, known as Monster Island, has become an invaluable source of data on how to deal with Kaiju. The extensive video monitoring of the islands, provides both security and study allowing the EDF to update its Operational Information in real time. The video feeds however, are subject to constant hacking by the internet-based group, The Godzilla Prediction Network.
Several other islands in the Pacific are suspected of once being somehow influenced by Nullius Ager. Strong suspicions surround Farou Island, with its own famous resident, but so far, they lack strong evidence. The earthquake in 1973 caused by Seatopia, damaged parts of Ogasawara, causing several Kaiju to temporarily flee to neighboring islands, which led to many violent conflicts.
Multiple efforts by parties in the Untied States, Australia, Russia, and Japan to see the islands destroyed with all monsters on it, have been advanced for decades, most famously, the 1968 D.A.M. compact. Most people however, consider Monster Island to be a marvel of nature and science, and in 1979, was declared the 9th Wonder of the World.