Archer's identity is Arash. He is a famed bowman sung in Persian myths and accomplished the great feat of saving thousands of people during battle.

A hero of legend from ancient Persia. He brought an end to the 60-year war between the Persians and Turkish while serving under King Manuchehr, who was known as the last king of the age of gods in west Asia. This hero is the savior who brought peace and order to both these peoples.

(Source: Type-Moon Wiki)