Archer

Archer is the Servant of Rin Tōsaka. Archer is actually Shirō Emiya from one of the possible future worlds. He is ultimately the winner of the fifth Holy Grail War in his world, and is a living incarnation of the "Hero of Justice". The Throne of Heroes, which preserves the souls of all Epic Spirits, exists outside of any conventional timeline, so Archer can be called from any point in history. He is linked to the jewel used to save Shirō's life, which allows him to be summoned.