Yamatai

Yamatai is the name given to a Class M planet discovered inside the Dragon's Head Nebula by the USS Nautilus (NCC-31910) in 2407. (Star Trek Online: Valkyries)

Description
Yamatai, as seen in the 25th century, was a very Earth-like planet in most respects, the most obvious exception being that its surface was composed of 89% water, leaving it with less than half of Earth's total land mass. Most of this land was split into islands scattered around the globe.

One of these archipelagos, in the north-eastern hemisphere, had a main island (known simply as the Main Island, to its inhabitants) that was nearly 20 km across, well-forested and extremely mountainous. This island contained abundant underground deposits of verdenicine gas. ("Survivors of Yamatai")

Original inhabitants
Around the 4th century BC, Yamatai was home to a race of humanoids who had created an early-warp civilization. The geography of the planet was very different during this time, with much lower seas, and humanoids built a research facility on a mountain that would later become the Main Island. They used the facility to research polaric ion energy, developing a crystal which could be used to focus and stabilize the energy. Unfortunately something went wrong at the facility and a catastrophic polaric ion explosion resulted, destroying all life on the surface of the planet (and possibly raising the sea-level).

A number of the humanoid inhabitants of the planet were transformed into energy beings rather than being killed outright, however the polaric energy they were composed of was inherently unstable and soon dissipated, killing them. Only one energy being managed to escape this fate by bonding itself with a fragment of the stabilizing crystal from the research facility. This being then commandeered a starship and departed for Earth, where it possessed a human woman and became known as the Sun Queen Himiko.

Japanese colonization
After ruling on Earth for four centuries, Himiko returned to Yamatai, bringing a number of her human subjects with her. She terraformed the desolate planet, introducing various Earth flora and fauna, including various deciduous and coniferous trees, deer, wolves, and crows. She eventually moved her capital to the Main Island on Yamatai (which was now truly an island). Her subjects built a monastery to worship her on the site of the original inhabitants' research facility and constructed a palace for the Sun Queen overlooking a valley nearby. Humans became permanent residents on Yamatai and numerous villages were built.

It was during this period that Yamatai received its name. Yamatai served as the capital of Himiko's primitive, but far-flung empire for over a century, but her reign came to an end when one of her priestesses, Hoshi, whom she had chosen to become the next host to her non-corporeal form, committed suicide in order to foil the transference of the energy being. Himiko became trapped in a decaying body in the Chamber of the Sun at the highest point of her monastery on Yamatai. Furious at her defeat, she used polaric energy to lash out, destroying the human civilization that had sprung up on Yamatai and creating dangerous storms in the surrounding Dragon's Head Nebula. The only remnant of the Japanese colonization were the ruins, preserved by being infused by polaric ions, and Himiko's Stormguard who were similarly preserved and acted to guard her at the monastery, but were no longer under her direct control.

Dominion War
For over 2,000 years, the Dragon's Head Nebula was a hazard to interstellar shipping. While this was attributed to the natural prevalence of ion storms in the area, the storms were actually caused by Himiko who used them to bring down any ship passing nearby on Yamatai and prevent crash survivors from leaving, even shooting down their craft with polaric ion discharges if necessary.

During the Dominion War, the Dominion took note of this natural hazard and realized it was not natural but artificially controlled. In early 2375, the Dominion sacrificed several cargo ships to establish an expeditionary force on Yamatai. The expedition's mission was to determine the cause of the unnatural storms and devise a way of controlling them, so that this control could then be used as a weapon against the Federation and its allies. The expeditionary force established a research base on the east coast of the Main Island and a communications base in the mountains on the west side of the island.

They tried a number of approaches to investigate the source of the storms. Ultimately the most successful was archaeological surveys of the Japanese ruins on the planet, which led them to the location of Himiko and the Star of Yamatai. Unfortunately, this also brought them to the attention of the Stormguard who attacked the Dominion expedition and wiped it out.

Solarii
Only a handful of Dominion personnel survived the Stormguard attack. Among them was a Cardassian record-keeper, Matan, who came to believe that Himiko was a goddess and was keeping him on Yamatai with her storms until he found a way to release her from her old body. To that end, beginning in 2386, Matan set up the cult of the Solarii made up of male survivors of subsequent crashes. He trained them to worship Himiko and to gather up human female crash survivors and subject them to the Ritual of Fire (attempted burning at the stake) in order to determine whether or not they were "the Chosen One"--Himiko's next host who would set the Sun Queen free and the Solarii with her.

The Solarii mostly used existing structures for their purposes, but did build a shantytown of scavenged materials in the valley beneath the Sun Queen's old palace, which became their new headquarters. The shantytown was built to neighbor a downed Romulan warbird, which the Solarii powered up using verdenicine gas taps. The Solarii also used gas taps to restore the old Dominion communications base to serve as the center of their communications network. They were careful to leave the Stormguard and the monastery alone.

In 2407 the USS Nautilus (NCC-31910) traced samples of ancient Japanese pottery back to Yamatai. The Nautilus deployed a shuttle to investigate, but it was caught in an ion storm and crashed. They deployed a second shuttle to rescue the away team from the first, but Himiko brought the rescue shuttle down as well. The Orion-controlled bird-of-prey OSS then attempted to retrieve the Starfleet away teams from the planet, but was also shot down by Himiko. Throughout this time, the survivors of these recent crashes clashed repeatedly with the Solarii. Eventually, following the research left behind by the Dominion, they traced the storms to the Star of Yamatai and the Chamber of the Sun in the old monastery. While the Solarii attempted to use one of the survivors, Samanatha Hayashi, as a new host to set the Sun Queen free, another survivor, Carlin Drel entered the Chamber of the Sun and destroyed the Star of Yamatai.

With the destruction of this stabilizing crystal, Himiko's polaric ion energy built up uncontrollably and was catastrophically released in an explosion that vaporized all life on Yamatai and caused subspace ruptures in the nebula around the planet. Starfleet predicted that it would make travel back the planet impossible for the better part of a decade. ("Survivors of Yamatai")