Source

Source is an artificial planet made from reflective metal that shines the color of tarnished silver. Its origin remains a mystery, save for the name scholars attribute to its ancient creators, the Progenitors. However, this unique planet is much more than a subject of idle curiosity to the inhabitants of the spheres. Source contains the system’s only producer of nectar: an ancient fuel believed to be liquefied starlight which is necessary to operate the system’s more powerful and essential artifacts.
Ever since the end of the first civilization, societies have fought amongst one another to control Source and its nectar. The Alliance was founded when King Nasser Graham seized the planet from The Undying Empress in an attempt to put an end to the constant warfare that plagues the system.

Geography

The planet's reflective surface rises to scolding temperatures when exposed to sunlight, leaving most of it unhinhabitable. However, settlements exist on its south pole, including the Alliance's capitol, Lion City. A pool of water functionally the size of a sea along with millenia of various civilizations building over the planet's original surface make the southern sea and its fixtures difficult to distinguish from those of a natural planet.
Actually setting foot on the planet, it would be impossible for a newcomer to make that mistake. Tremors, audible hums, and even entire blocks expanding or compressing are all commonplace as the titanic machines beneath the surface shift and sputter, or a buried ancient city finally falls into the planet’s liquid core. Telling a “native” Source resident from a tourist is as easy as watching their face when the ground beneath them sifts, since over time the “activity” beneath the surface becomes as mundane to residents as a cloud passing over the sky on any other planet.

Orbit

Equally curious is the planet's trajectory across the system. Technically, calling Source a planet is a misnomer, as it does not--strictly speaking--orbit the sun. Rather, it periodically shifts locations seemingly at random, usually settling over another sphere like a moon for centuries or millenia before it wanders off to find a new roost.
The Koan artificers and their advanced technology may have helped the Empire hold onto Source for an anomalously long 300 years, but the original conquest of the artificial planet is largely attributable to the fact that Source just happened to settle so close to (what were at the time) Republic controlled lanes and spheres.
Because of their polar location, the inhabitants of Source do not experience a “natural” night-day cycle; however the passage of one of four neighboring moons sends the sky around the city in to complete darkness for roughly six hours once every day, or roughly twice every day when Source’s orbit aligns with Io’s.
Two of Io’s moons, Spring and Topaz, serve as the intermittent gateway for the Homyn (and the occasional Mong Bal) into the city. Koa and Geit are afforded easier access from Sera’s two moons; Aspidai and Hastati, which provide lanar ingress to the city throughout the entire year.

What Lies Below

What Source's habitable zone lacks in surface area, it makes up for in depth. The planet's geography is divided between two zones--the oversea and the undersea. Beneath the "surface" travelled by most who visit the sphere, lies a deep and vast layer-cake of ancient ruins, some of which adjoin subterranean oceans.
As the system's only font of nectar, countless civilizations established settlements and capitol cities on its surface--which slowly sink into the planet's depths as its tectonic gears shift. Intrepid explorers often travel to the undersea in search of undiscovered nectar wells or artifacts from ancient civilizations. Those who do so, however, should be ready to face the protectors those ancient civilizations left behind, whether they take the form of patrolling automata or vengeful spirits.

Ecology

Source's ecology reflects the diversity of the many civilization that have inhabited it. While lacking native life of its own, the planet hosts several ecosystems born from imported animals. Some are domesticated or game species native to other planets, such as Tyrant's strider hounds or Mong Bal's Titan Koi, while others are ordinary animals that speciated over time and exposure to nectar radiation into unique forms, such as the massive Queen Crabs who guard sandbars over Source's seas.
The undersea also sports a population of "native" mutants created from exposure to nectar radiation. Most trips into Source's bowels are relatively harmless, however over generations, exposure to nectar can cause genetic drift and mutation to the point where they no longer consider themselves part of the races of their ancestors who originally colonized source. Some of these mutants' lineages are easy to spot, like the scurrying Bridge Goblins who still bear a striking resmblance to their Koan ancestors. Others, prove a bit more difficult owing to a more ancient lineage or more severe exposure to nectar, like the thin and ghostlike Pale Men.
The mutants beneath Source adhere to a variety of customs. Some are disinterested or friendly to visitors beneath the surface, others hostile, and still more are elusive subjects consigned to urban legend, a menagerie of cryptids unique to the machine planet. Many mutants follow the rule of King Kaloo --a seemingly immortal being blessed with regenerative properties. However, his reign is better seen as controlling a strong plurality of near-surface mutants rather than the ruler of all who live in the lands beneath Source. The machine planet's endless undergrounds certainly hold many other civilizations barely glimpsed by surfacers--perhaps as varied as the many cultures who inhabit the spheres themselves.

Maps