Prester John, also referred to as a Presbyter, was the subject of a legend popular in Europe throughout the medieval period and Renaissance. It envisaged a godly king who was said to be a descendant of one of the Three Magi. He represented the possibility of a universal Christendom, as he was thought to rule over a king in the East - variously in India, central Asia or Ethiopia - among Muslims and other religious groups. Myths of this virtuous ruler became associated with other longstanding idyllic places: some retellings saw his kingdom as the site of the Gates of Alexander, the Fountain of Youth or even the Earthly Paradise, the Garden of Eden.
Editors. "Prester John". The Literary Encyclopedia. First published 31 July 2012
[http://www.litencyc.com/php/stopics.php?rec=true&UID=1423, accessed 23 March 2017.]