Sayshell was a planet in the Periphery. It was the capital of the Sayshell Union, which was renowned for having resisted the control of the Foundation Federation for several hundred years during the Interregnum, despite being completely surrounded by Federation territory. Sayshell features heavily in Foundation's Edge.
According to the legends of Sayshell, the planet was founded by a group of colonists who were not known to hail from any other colonized world, leading some historians, such as Janov Pelorat, to conclude that Sayshell was a colony founded directly from Earth. The Sayshellians themselves believed (incorrectly) that Earth was located somewhere within Sayshell Sector.
Due to the protection of the mentalic planet Gaia, Sayshell was never truly threatened by outside forces for all of its history. Under the Galactic Empire, Sayshell received minimal taxation and enjoyed a large degree of independence from Imperial controls. Later, after the fall of the Empire, Sayshell remained untouched by the anarchic war which consumed most of the Galaxy, and eventually from the control of the Mule's Union of Worlds and the Foundation Federation.
Sayshell was briefly threatened by the Foundation Federation under Harla Branno, who in reality wished to destroy the planet Gaia (which lay completely within Sayshellian territory). However, Gaia used her mentalic influence to convince the Sayshellians that, in the end, Mayor Branno was looking for a neutrality-trade treaty, marking the end of Sayshell's brief stint in galactic affairs.
Sayshellian culture was noticeably different from that of the ultra-scientific Foundation Federation. It stressed mysticism (especially the influence of dreams) and the respect of nature, as evidenced by the percentage of Sayshellian wildlife that was still preserved from human influence. Sayshellians also had excellent cuisine, and a minor dislike toward outsiders, especially Foundationers. The religion and philosophy of Sayshell seems to be modeled on Buddhism.