Archer (Unlimited Blade Works)

Archer is one of the antagonists of the Unlimited Blade Work Route and unlike the other two routes he is on the antagonist side

Past as Shiroe
Archer is not a proper Heroic Spirit in the sense of other heroes. His true identity is that of Shirou Emiya of an alternate timeline from that of Fate/stay night who made a contract with the world and became the Heroic Spirit EMIYA. He acts as a Counter Guardian for the world as payment for the contract. He is summoned because he still has the jewel pendant that Rin used to save his life after Lancer stabbed his heart. The jewel he owns is the actual catalyst used for his summoning rather than the one that Rin still has at the time of his summoning. After the end of each of the three routes in Fate/stay night, the possibility for Shirou to become Archer still exists, but the chance is it happening is close to zero.

After winning the fifth Holy Grail War along with his Servant Saber, Emiya Shirou was all the more inspired to pursue his dream of becoming a superhero. To this end, he stubbornly trained himself to his peak and began working as a freelance magus similar to his father. It was during this time when he received his signature red overcoat as a gift from Ciel of the Burial Agency. In order to save the lives of a hundred of people dying before him in a calamity, for the sake of saving the lives that his eyes could see and for the sake of saving even more lives as a Heroic Spirit after his death, he made a contract with the world and became a hero. Although he desperately fought to end a war, he was in turn branded as the mastermind behind that war and subsequently executed. His belief that he would continue to save many people as a Heroic Spirit did not happen, but rather he was made to clean up after human actions and forced to take many lives to save humanity as a whole instead. After seeing human self-destruction and forced to oppose his own ideals countless times, he began to deny himself and his ideal. Even knowing that the Throne of Heroes was isolated from time and space, Archer desperately came to believe that his only hope of release was to have himself summoned into an era where Emiya Shirou exists and kill his past self, hoping that the double paradox created by Emiya Shirou being killed before having a chance to make the contract with Alaya and that the killing was done by an Emiya Shirou which successfully made the contract with the world would create a time paradox great enough in magnitude that could potentially erase his existence as a Counter Guardian.

The Fourth Grail War
On the night of the second day, his statement that his memories were vague and he didn’t know his identity due the imperfect summoning was halfway true and halfway false. He no longer possesses Shirou’s memory, although he can still remember some key events such as being saved by Kiritsugu Emiya and meeting Saber. While Rin slept, he reasoned out his situation and realized that he may have the opportunity to achieve his goal. This was affirmed when the girl who summoned him introduced herself as Rin Tohsaka the following morning.

Archer betrays Rin, aligning with Caster because, he claimed, she had the highest chance of acquiring the Holy Grail.

He then betrays Caster and her master and kills them both, revealing his true intentions. Archer needed to be free from Rin's command seal in order to accomplish his goal of killing Shirou. Archer then kidnaps Rin after she forms a contract with Saber, forcing a situation where Shirou faces off one on one against Archer.

Archer loses the fight, but only because he does not attack Shirou as he is stabbed through the chest. However, he survived the blow thanks to Independent Action, and remains hidden until the final battle where he saves Rin from the Holy Grail and eliminates a cornered and near-defeated Gilgamesh.

He then disappears for good with a smile on his face, confident that Rin will stop Shirou from taking a path that he will regret.