The mythologies of the Turkic and Mongolic peoples are related and have exerted strong influence on one another. Both groups of peoples qualify as Eurasian nomads and have been in close contact throughout history, especially in the context of the medieval Turco-Mongol empire. The oldest mythological concept that can be reconstructed with any certainty is the sky god Tengri, attested from the Xiong Nu in the 2nd century BCE. Geser (Ges'r, Kesar) is a Mongolian religious epic about Geser (also known as Bukhe Beligte), prophet of Tengriism.