Rider's identity is Ramesses IIm the third pharoah of the Nineteenth Dynasty of Egypt. He likes to refers to himself as the King of Kings, and also prefers being addressed as Ozymandias by other Servants and people. He was friends with Moses in his life, and hold a special place in his heart for one of his wives, Nefertari. However, it could be that their friendship ended when Moses became prophet of the Israelites and began to preach the teachings God, denouncing the gods of Egypt. (Source: Type-Moon Wikia)