What other nomadic people migrated throughout Asia and established a large empire?

In the early 13th century the Mongol Genghis Khan consolidate most of the nomads on the steppe.

a social contract.

"a social contract is an agreement between citizens and their leader where the citizens give up certain freedoms in exchange for protection. the constitution of the united states is an example of a social contract."

adopted the practice of proskynesis, a persian court custom that involved bowing down and kissing the hand of others, depending on their rank.