Formerly the gateway to the Sith Empire, Ziost is but an icy reminder of past Sith glory. Located in the Stygian Caldera's northwestern reaches, the planet Ziost is one of four planets in the system of the same name. Although vast, ancient forests and tundra once covered the planet, the Sith species' arrival and subsequent mass deforestation transformed the surface, making it akin to the tomb worlds Korriban and Dromund Fels. Ziost owes its current appearance to an ice-age some 5,000 years ago, the result of a deviation from its orbit. The subsequent planetary glaciation left massive swathes of ice covering much of the surface, broken only by spots of geothermal activity, which, in some places, has allowed forests to spring up once more on the otherwise desolate world.
The Sith species first colonized Ziost some 27,000 years ago in a mass exodus from their home planet Korriban, following centuries of internal strife, and the planet flourished in the millennia that followed. The Sith used their adopted homeworld as neutral ground where feuding factions could meet to discuss matters concerning the Sith domains. This role secured Ziost's significance, even as these domains expanded, and Ziost became the capital of the First Sith Empire approximately 7,000 years ago. That Empire's fall, coupled with the planet's sudden glaciation, rendered most regions uninhabitable and left Ziost largely lifeless and forgotten. The New Sith Empire later recolonized Ziost as a key trading hub, giving it the nickname "Gateway to the Empire", but the planet never regained the prominence it had once held as the undisputed capital of a vast stellar dominion.
Following the Sith Order's complete disappearance approximately 1,000 years ago, the planet lay forgotten once more. Wildlife retook the planet's surface during this period, though it can hardly be said to flourish in the vast ice sheets covering Ziost's surface. With the rise of the Galactic Empire, limited resettlement has been achieved, mostly concentrated around the planet's equator; however, travel to and from the surface is still heavily restricted. Access is only granted to a select few Imperials. Archaeologists from the Imperial University supervise various excavations, endeavoring to uncover what remains of the ancient cities, temples, and fortresses which once peppered the surface; while the Sith Order is also rumored to have established a presence on Ziost (perhaps seeking to discover the secrets of their predecessors). Among the points of historical interest are the ruins of the Citadel Complex atop Mount Midwan, edified to serve as the administrative heart of the fledgling Sith Empire, and the derelict temple of the Sith Emperor, where, for centuries, cultists gathered to worship the Sith ruler as a deity.
Ziost's few permanent inhabitants face numerous challenges. Vast glaciers, several kilometres thick, make dwelling underground extremely impractical, while their surface is frequently ravaged by winds of almost 200 kilometres per hour. The planet's average temperature hovers around -30° standard all year round. Life on the planet is therefore centered around the geothermal hot spots, where temperatures can reach as high as 15° standard, allowing miniature ecosystems to develop, relying on what little surface ice has melted in the area and providing fertile ground for cities to grow. These hot spots, in stark contrast to the barren wastes dominating the rest of Ziost, boast a diverse array of flora including several types of moss and fungi. The most unusual native specimen is the unique ror`jhan tree, known for its needles which secrete a fast-acting necrotoxin lethal to most living organisms. Dangerous fauna is rare, as the limited habitable regions do not provide enough territory to sustain larger predators. Most of the indigenous animals are small herbivores. The only notable exceptions are the predatory vine cats which, while few in number, pose a significant threat to any errant settlers unlucky enough to happen upon a pack.