The world of Zothune, started as a Dwarven mining colony, has been abandoned to fate by the Pact Worlds, in order to prevent an extended conflict with the Azlanti Star Empire. Taking up the name of a group of ancient Dwarven defenders from Golarion, the Gardathir must defend this harsh world with limited resources and too few personnel against the Azlanti while avoiding Pact World military units tasked with arresting them as "agitators."
Zothune is the closest world in the system known as Firehelm by the Pact Worlds. The planet is tidally locked, meaning the same side always faces the sun, a low-luminosity red dwarf star. The far side of the planet is frigid, since it never sees the star. Its only source of warmth is winds from the warmer half of the planet. Even so, the cold side regularly sees temperatures below −100 C.
On the sunward side of Zothune, water ranges from near-boiling to vaporous, when it is present at all. Surface temperatures can exceed 200 C.
In between these two "halves" of Zothune is a thin ring of habitable zone. This ring is but a few hundred miles at its widest point, and thins to just over 20 miles at the southern pole. Here, water can be found in a liquid state, and one sees an odd type of water cycle, with glacier-like constructions on the dark side being continually melted by the warm air blowing in from the hot side. Melted water flows in gigantic rivers to the hot side, where it evaporates and cycles back around to fall as snow on the cold side. It was here, in the habitable zone, that the original Dwarven colonists settled for mining expeditions both within the habitable zone and just beyond either side of it.