Elionois, Leonois, Lyoness
The ancestral land of Tristan, ruled by his father Rivalin or Meliadus (Meliodas).
Its early history is supplied by the Prose Tristan describes its history, including Kings Pelias who was succeeded by hit son Lucius, who in turn was succeeded by Apollo, who unwittingly married his mother but later wed Gloriande, by whom he became the father of Candaces who, in time, became king of both Liones and Cornwall.
It was thought to lie between Cornwall and the Isles of Scilly, and to have sank into the sea, this is identical to Lyonesse. It is perhaps identical to Marie de France’s Leon. Despite its given location, the name is probably a variation of Lothian, besides, in the Vulgate Version, Lot is said to be one of the early Kings of Liones, which would seem to suggest that Liones and Lothian are the same..
In some versions of the Tristan legend, Tristan makes his tutor, Governal, king of the land. In Tennyson, it seems to be Arthur’s kingdom, and it is the site of Arthur’s final battle with Mordred.
Sources
Prose Tristan | 1230-1240
Idylls of the King | Lord Alfred Tennyson, 1859-1886