The Sayshell Union was an interplanetary confederation that existed during the Interregnum. Located in the Periphery near the central regions of the Foundation Federation and with its capital at the planet Sayshell, the Sayshell Union was notable for resisting all types of military, political, and economic control.
The Sayshell Union came into existence shortly after the collapse of the Galactic Empire, although Sayshell Sector had always been a relatively low-tax, left-alone territory during all the years of Imperial control. The Union apparently went unscathed through the early centuries of the Interregnum, and was left in peace even by the Mule during his wars of conquest.
The biggest threat by far to the independence of the Sayshell Union was the Foundation Federation, the economic and political influence of which it tried desperately to resist. Although under Mayor Harla Branno the Foundation and Sayshell almost went to war, at the conclusion of a brief conflict they signed a neutrality treaty which cemented Sayshell's unique position in galactic affairs.
The true reason for the Sayshell Union's untouchable status was the presence of the mentalic planet Gaia within its borders. Through the application of her mentalic field, Gaia was able to, for most of history, deter exploration and therefore any possible threat to herself by keeping Sayshell a neutral backwater.