The Mongols, added to Civilization III in Play the World, have the Keshik as their unique unit. They replace the Knight, which is obtained through Chivalry. They cost 60 shields. Their attack/defense/movement ratio is 4/2/2, which is a downgrade because the Knight's ratio is 4/3/2. Unlike the Knight, however, Keshiks do not require Iron in their strategic resource box to create; they only need Horses.
The skill of a Mongol on horseback was notoriously keen. Having been taught to ride on horseback from the age of three, and by five given bow and arrows to use from horseback for hunting and war, it was a natural way for the Mongols to conduct war. The Mongol's harsh, nomadic lifestyle had prepared them well for the rigors of war; they often thrived in conditions that would be considered intolerable by any other military of its time. When the need arose Mongol horsemen could last up to ten days at a time without cooking food, during which they would sustain themselves by drinking the blood and milk of their horses.