Viewed from space, Illarreen Prime appears to be a fairly typical gas giant, with swirling bands of cobalt blue, violet, aquamarine, and turquoise interspersed with glowing white and pale yellow. The whole planet is covered in a network of linked floating cities, which appear and disappear from view as the coloured clouds whip around them. On closer approach, a pilot will notice an oddity: none of the floating cities are domed or shielded. Illarreen Prime is a rarity—a gas giant that holds a layer of oxygen and other breathable gases and is capable of sustaining life for many sentient species. Many of the floating cities occupy this zone, which is approximately five kilometres deep, as the oxygen-rich layer negates the need for expensive filtration and oxygen supply equipment. This factor alone reduces the operating cost of a floating city on Illarreen Prime by as much as a third compared to comparable cities on other, more typical, gas giants.

Illarreen Prime completes a rotation around its axis, which is tilted at an angle of nineteen degrees, every twenty-seven standard hours and a complete orbit of the system’s star every six hundred and eighty days. With relatively unoffensive average temperatures for a gas giant, life is somewhat more comfortable for the billions of sentients that call Illarreen Prime "home". The planet’s main industry is the extraction and production of tibbanagas, with every city boasting a number of factories, refineries, and warehouse/transport facilities. The second-largest industry is food production, with billions of cubic metres of space dedicated to hydroponics and the farming of edible fungi. Animal husbandry is quite limited, which is unsurprising considering the lack of any solid planetary substrate, although small-scale farming of edible rodents does take place in many cities. These rodents provide a welcome change from the workers’ usual fair of tank-grown greens and fungi, and the industry is growing quickly. The system government plays a part in helping new industries take root by providing generous subsidies as well as favourable tax rates for innovative products that can enliven the otherwise mundane lives of the planet’s citizens.