The planet Chymus is a toxic hellhole. Its oceans are acid, reaching a maximum of pH of 4.5 at the poles, and awash with toxin-secreting microorganisms. The atmosphere is 10% carbon dioxide, warming the globe beyond an Earth climatologists’s worst nightmares. The few spots of dry land that do exist are uninhabitable when below sea level– CO2, heavier than the rest of the atmosphere, collects in the lowlands and transforms them into anoxic death traps. Any unfortunate oxygen-breather that wanders into a valley is swiftly suffocated. Not that breathing in oxygen-laden areas is safe, either; the acid is found in the soil and rains from the sky. Any unprotected, unaugmented organic would last no longer than a week before succumbing to lung damage. Even synthetic life isn’t safe; the pH can damage most casings over time.
Still, Chymus is teeming with life. All native organisms are well-acclimated to the acidic conditions, and both complex flora and fauna are present. Most of this diversity is in the ocean, but freshwater and dry-land animals exist as well. The anoxic death-valleys are popular with exotic flora and anaerobic bacteria, and most terrestrial animals have no issue extracting oxygen with their highly efficient lungs.
Regardless of environmental hazards, the appearance of the planet itself is striking. Firstly, Chymus has a small ring system that is visible from the planet’s surface. They make the planet measurably more difficult to land on, and present issues when attempting to establish satellites, but any fleet sufficiently familiar with navigating around the rings will find they have a territorial advantage against foreign invaders. Secondly, Chymus is host to several native species of green “algae,” which exist in such high concentrations near the planet’s equator that they stain both the ocean and the sky green. The effect is so extreme that it is visible from space; locals have named this green area of the planet “The Bile Seas.”