Song of Yste - a book of “preglacial” origin (Thulean? — it was known to the antehumans of Thule according to the Book of Eibon ) which was translated in mediaeval times into Greek, Latin, Arabic and Middle English by the Dirkas Monks. It may have taken the form of a classical epic poem (it is compared to the Hindu epic poems), although the poetry has been lost in translation and it is now a rather dull, heavy read. It seems to mention the antehuman land of Arkya.
The Song of Yste was created by Rober A. W. Lowndes; and expanded on by Lin Carter and Laurence J. Cornford.