High Sky, sometimes known as Upper Sky, was the topmost layer of the atmosphere in the Edgeworld. It began at the altitude of the top of the Loftus Observatory and included the infinite expanse of sky above. During the age of the Sky-Scholars, High Sky study was the most fashionable discipline in Sanctaphrax. According to Stob Lummus, dust particles in High Sky were responsible for the glowing quality of sunsets. High Sky was where the Edge's gulf stream was located.