Cosia was located in Cosian Space, a region of the Deep Core, the innermost region of the galaxy, in a star system that shared its name. The planet was the only inhabited world in the system, which was home to only one star. Cosia had two moons, Tabu and Tebu, which were in full view in the nighttime sky.

The planet was covered in rolling hills that were home to the immense cosa tree, which made up the planet-spanning forests. The cosa tree produced massive palm leaves, over a hundred meters in length. Within those forests were numerous Cosian cities, like the planet’s largest—Nu-Cosa—that were built into the cosa trees. The homes in those cities were connected by finely carved wood stairways, and walkways of etched planks and cultivated vines.