The universe is populated by thousands of ring worldsdrifting in space. Each ring wraps around a single pulsating star which provides its sunlight. All of these rings themselves were once part of a much larger structure, similar in design to an O'Neill Cylinder
The ring on which Austraeoh takes place, which from henceforth shall be termed "Urohringr", drifted into "...a chaotic patch of space" over 100,000 years ago and was overrun by chaos energies. At approximately this same time, the ring was broken into pieces in a cataclysmic event called "The Sundering".The edge of the "organized" universe, or in other words, the inner surface of the universe's sphere, is called the Plains of Harmony by the alicorns. It is their birthplace and the source of light and life to all.