Illium is a classic garden world, developed to serve as entrepot between the Terminus Systems and the Asari Republics. To abet this trade, the normally stringent customs laws of Council space on product safety, proscribed materials, and sapient trafficking are relaxed. Officially Illium is not an asari world; it is colonized and operated by asari corporate interests. This gives it the same legal latitude enjoyed by the human corporate research enclaves of Noveria.
Illium is one of the youngest asari colonies settled during the 7th Expansion Wave. The world is hot and massive; ground settlement is only possible at the higher polar latitudes. In more equatorial locations, the population is housed in arcology skyscrapers to escape the heat of the surface.
During the First War, Illium was conquered by the Combines and reduced to ruins with it's enhabities enslaved. this planet servived the combines as a location of one of four Catherdels that was located in the Riz'ro Universe during the early years of the First War and when the newly created Citadel Alliance invaded the planet they then destoryed the Catherdal, destory the first of four