Archer

Rin Tohsaka: Master
Illya and Berserker: Enemies, rivals for the Grail
Shirou Emiya and Saber: Temporary allies
Lancer: Rivals

The Servant of Rin, due to a summoning issue he has been left with amnesia and has no idea what heroic spirit is supposed to be.

His weapon of choice are two seemingly mundane daggers.
A bowman who fights with swords.
A cynical and sarcastic man.

That is all that is known about this enigma of a man.