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Riyona was an ancient empire that stretched north of the Sern River in Timandra.  Its fall (roughly a thousand years before the Moth saga begins) marks the beginning of the common Timandrian calender.

Riyona stretched across a vast area roughly analogous to the current kingdoms of Arden, Verilion, Mageria, and Orida.  All those four kingdoms currently speak dialects of the old Riyonan language.