Ydahr is a gleaming opal of a world, blue and green, aswirl with clouds that drift over a surface almost totally swamped in seawater. Ydahr is the homeworld of the Ydahri and the G’ahnli.

The predominant terrain type on Ydahr is the swamp or bog, which extends even to the frozen polar caps.

There is a thin layer of water across most of the planet, in some places opening out into chained lakes and small seas of various depths.

The closest one comes to land masses are tight tangles of vegetation, similar to those created by mangrove trees on Sol III.

The lack of a large axial tilt reduces the effects of seasons, providing a transition from a rain season to a drizzle season as the Ydahr year progresses.

The swamps of Ydahr have high animal, fish and plant life form readings, of a wide variety of species ranging from plankton herds to large carnivorous predators.

The dominant species are the Ydahri themselves, an amphibious intelligent life form. While extremely low in mineral resources, Ydahr has a high concentration of natural resources, ranging from exotic fish and crustacean-like creatures for food export to rare plants and biological compounds that could be useful in medical research.