One of the smaller planets in the Rrulinn system, Rrulinn IV is a study in contrasts. Although more than half of the planet is a frozen wasteland, magma blisters from beneath the planet's thin crust make over a third of the surface uninhabitable. And while poisonous gases force most of Rrulinn IV's inhabitants to take cover in domed shelters, they are the primary reason the planet is inhabited at all.

Activity on Rrulinn IV is focused on the areas where rising magma pockets meet the slow-moving glacial flows on the surface. At these locations, toxic phenodain gas released from the melting ice reacts with methane rising from the magma pockets to form an inert substance called tarocin. A remarkably lightweight crystal with a smooth plasticine texture, tarocin is useful in a variety of applications from large prefabricated windows to small decorative figurines.

After the first samples of tarocin were documented by an Old Republic geological survey team, a number of small manufacturers established collection bases and later developed a process for refining pure tarocin, free of the impurities found in naturally-occurring tarocin. In yet another contrast, these industrial interests were soon followed by a handful of small artist colonies.

Because the artists preferred to continue using the natural tarocin eschewed by the industrial manufacturers, the diverse groups managed to form a mutually compatible relationship. Together, they established the port city of Blue Sky, named for the ionization effect of the force field that keeps out the planet's toxic atmosphere, from which to ship their wares to the galaxy at large.