Ruten is the primary world of the material plane in the campaign. It is the center of all the current and foreseeable future story arcs, and is the focal point of the gods' attention. Unless something drastic happens, while on the material plane, Ruten will be the only planet the players visit.
Ruten has drastically different terrain depending on where you are on the planet. About 60% of the surface is covered by water, with the rest being covered by land and ice.