The author deals with a set of problems related to formation of empires as super-ethnic entities. The author accepts cultural and linguistic diversity and co-existence of religions as indispensable properties of empires. However the crucial property of an empire is the single ideology and strictly regulated state cult. In all epochs an empire as a fact of the world history presupposes the domination of a single idea, one universal mythology. The author points out that with no answer to the question what was the specific essence of the Mongolian empire and the ulus system which emerged all over the Central Asian space it is impossible to understand the subsequent development of separate states that existed with the Mongolian sphere. To answer the question one has to reconstruct the very mythology of the Mongolian empire. Religious toleration and ability to integrate more and more tribes and nations within the sphere of the Mongolian empie’s influence were determined by enormous impact Tengrianism had as the state religion and a complex cult. Mongols of the Middle Ages perceived the earthly and celestial worlds as the indivisible unity which could not be decomposed.