|Voice actor:||Yuichi Nakamura|
|Character type:||Servant (Master: Unknown)|
|Addresses self as:||Ore (我, ?)|
Archer is an alternate version of Gilgamesh, the king of Uruk and the hero from humanity’s most ancient epic.
Archer is still the most self-centered person in the world like his Fate/stay night counterpart, but he lacks the same kingly temperament and he is able to properly read the situation around him. While he is not an evil person, he has a callous personality. He has no real interest in the Holy Grail, so he instead wishes to establish himself as the strongest of Heroic Spirits. He finds incomparable joy in the battle of heroes splendidly fighting each other to the death for a miracle, and is angered by the fact that such an event never happened during his lifetime. Due to his Master’s influence, he is a Servant accustomed to the modern society.
He falls in love with the glasses-less Ayaka Sajyou much like a typical shoujo manga. Unlike his counterpart's haughty declaration that Saber will become his possession, Archer proposes to Ayaka in a somewhat more normal manner. He finds her beauty to be incomparable to even that of the women of Uruk, who had never won his approval during life. In contrast, he bitterly detests ■■, whose name is left blank, due to the similarities he sees between her and Ishtar. He believes “women who are absolutely confident in their good looks are repulsive creatures!”
He, as the "best and strongest hero under the sky", wishes to be the highest ranking Servant. Having two above him enraged him to the point where he wanted to kill his own Master, but he decided to forgive Berserker because he did not hesitate to sacrifice his reasoning to seek power. He instead focuses on Saber, referred to as Holy Blade Wielder (聖剣使い, Seiken Tsukai?), as his target, seeing him as a formidable opponent. Though his Master commands him to simply let Saber perish on his own, he thinks that a disgustingly formidable opponent is more precious than gold. Wanting to kill another person from the bottom of one’s heart is something that can only be experienced once in a lifetime. He is still quite cocky towards him, telling Saber that he should smile at being Archer's opponent even with his Master on the verge of death, else he deserves to be trampled upon.
While it is unknown if he still retains it in Fate/Prototype, he had a Noble Phantasm in the planning stages of the original novel that imparted the ability "Absolutely Survive" (絶対に生き残る, ?). It would have clashed with Berserker's Noble Phantasm at the time, which was to "not lose for eleven battles." The concepts of the two abilities clashed and the paradoxical situation had to be resolved. Berserker eventually died even though he won, while Archer lost but survived.
Archer is the prototype version of Gilgamesh that was to be used in the original Fate/stay night novel that was penned and left uncompleted. He was only briefly mentioned in notes detailing the plot of the novel, and received an expanded role in Fate/Prototype. He is summoned by the unnamed owner and president of a skyscraper that overlooks the city. He dislikes his Master's methods, calling him a boring man. As a person careful to the end, he is a coward who will miss a good show like Archer's fights by using indirect methods.
While Saber and Ayaka fall into a romantic mood as they are alone in her classroom, Archer suddenly enters and begins a passion-filled speech on the Holy Grail War from atop the teacher's desk. He declares two things about the War leave him unsatisfied, their rankings and Ayaka. He, as the Archer-class Servant, is ranked third, while Saber is ranked as first among the seven Servants. He is currently focusing on Saber to obtain his rightful ranking, and he declares his attraction to Ayaka, telling her to become his empress once he overthrows Saber. Saber, displeased by the display, downplays it as insane talk, so Archer challenges him to show their difference in power with Enki.
After a week, Ayaka ends up poisoned by Sancraid Phahn, and Saber, while searching for him, meets Archer within the downtown subway at midnight. Challenging Saber with an arrogant, proud expression, he presents a medicine that can cure any poisons hurting her even if he doesn't actually know the specifics of them. Using that to issue their final duel, he tosses the bottle toward Saber and races towards him while wearing a fierce smile. As they fight through the subway to open air, they dogfight between the skyscrapers of Fukutoshin while engaging each other.
It is a close battle between them, and as each has met the conditions to unleash their final weapons, they are each looking for an opportunity of sure-kill. Once they reach the end of their fierce melee, Saber is knocked to the ground and Archer obtains his chance from atop a skyscraper. Summoning Enki, he seeks to overwhelm Saber with the tsunami. He is so exhausted that he can hardly move, but still manages to laugh as if it is the duty of the victor. Saber tells him it is too early to celebrate, unleashes Excalibur, and cleaves through not only Enki, but the arrogant king as well, as he sighs with despair at his defeat. He is not killed during their battle, and it is noted he later goes on to crush Berserker.