Keystone is the second planet from the star Camos, the densest planet in its star system, and the only planet in the Camos system with complex indigenous life and a readily-habitable ecology and environment. Its native ecology is estimated to have formed from the development of single-celled life some 4 billion years ago. The planet itself is estimated by geologists to be 5 billion years old, roughly a billion years older than the Earth.

Life was able to flourish in part due to its placement from its star, a strong geomagnetic field, the presence of an ozone layer. The presence of living organisms allowed the formation of a layer of ozone in the atmosphere, shielding its nascent ecology from the most harmful of its star's radiation. Since half a billion years ago, life began to grow ever more diverse, and Keystone hosts some of the greatest native biodiversity in the Outer Colonies. Keystone is home to some 6 million species of organisms, though some of the most populous complex organisms are invasive species not native to the planet.

Approximately seven centuries ago, Keystone was discovered by Terran astronomers. In the early 2700s, the Terran Empire mounted a century-long research and survey expedition with a few hundred people, establishing the first human settlement on the world at a site that would later become the city of Fort Dusken. In 2811, a full settlement expedition was launched after the planet was properly studied and surveyed, consisting of 5,000 settlers. These settlers were drawn primarily from people of Russian and Northern European ethnicity, though many other ethnic groups composed the demographics of Keystone's early settlers. The population steadily rose over the centuries as a few major cities were founded and thousands of towns were created. Today, Keystone claims a population of around 1.1 billion people, who depend on the planet's native biosphere and minerals to provide a self-sufficient living. The population is mostly concentrated in the equatorial belt and its many waterways, with gradually less dense population outward from the equator. Lakeside City, the planet's formerly-most dense and populous city and home to over a million people, was destroyed in the Keystone Incident of 3280; some ten million people in total perished in the incident and over twelve million were displaced or seriously injured. The planet's population has mostly recovered from the violent events, and now hosts its capital at Port Glimmer in the Oka Islands. The planet's economy is dominated by agriculture, light industry, tourism, and technology, with extensive exports of finished goods and agricultural products. Despite this, it still lacks a space elevator and accompanying infrastructure. Instead, its external economic activity is conducted by use of ground-based space launch facilities and a network of orbital stations.

Keystone's lithosphere is, as in many garden worlds, divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. Almost sixty percent of Keystone's surface is covered with water in the form of large polar ice caps, turbulent narrow seas and the large, calm Oka Ocean, with the remaining surface consisting of continents and islands that together have many lakes and other sources of water that contribute to the hydrosphere, including the Great Marian Lakes and Lake Orange. The landmasses tend to be dominated by stout mountains, arid tundra, and temperate prairie, with swamps and rainforests most abundant at the equatorial band. Foreign planting and settlement has led to the proliferation of invasive tree and other plant species. The majority of its native plant life consists of xenograsses, mosses, and low shrubs. The planet's age has led to a more stable volcanic geology and largely eroded the vast mountain ranges. Rainfall is light but even, lending to the world's productive agricultural economy. It has also staved off the worst effects of desertification. Its poles are mostly covered with ice that includes ice sheets and sea ice, with widespread glaciation across its northern hemisphere; Keystone is considered by its geologists to be in the midst of an ice age. Its interior remains active with a solid iron inner core, a liquid outer core that generates the magnetic field, and a thick layer of relatively solid mantle.

Keystone gravitationally interacts with other objects, most notably its star Camos and its only natural satellite, Voussoir. At one time in its distant past, Keystone possessed another satellite formed from the impact that produced Voussoir as well as the Oka Ocean impact crater. However, this satellite was unstable in its orbit and collided with Keystone, forming the Oka Islands. This long-disappeared moon has been tentatively referred to by astronomers as "Fallstone". Voussoir's gravitational interaction with the planet stimulates ocean tides, stabilizes its axial tilt and rotation, much like Earth's moon. Voussoir is, however, smaller in comparison to Earth's moon and hosts only a small research facility and a military outpost, with no extensive settlement.

Keystone is classified as a Colony world, and is overseen by the Department of Colonial Affairs within the Ministry of the Interior. It is locally administered by an elected governor and legislature, with civil and judicial authorities appointed by the planetary government. Its current governor, elected in 3282, is native Artem Meshcheryakov.

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