Archer is an Archer-class Servant able to be summoned by the Protagonist in the Grand Orders of Fate/Grand Order.
Archer's True Name is Euryale the Far-Flier, the second daughter of the Gorgon Sisters and the younger sister of Stheno and older sister of Medusa, who were goddesses born from the wishes of mankind for ideal idols, the embodiment of the yearning hearts of men. While she and Stheno were "perfect goddesses" who would not age, Medusa had some kind of flaw that allowed her to grow. They should have been three united sisters, but this divide allowed them to become three separate individuals. While Medusa was different from the start, her existence also brought irregularities in the two who were still the same. Due to the jealously of Athena, Medusa was cursed, had the faith of her followers taken away, and was banished to the Shapeless Isle as a monster. She called Stheno and Euralye monsters because they would never grow old, but that was a lie to cover the fact that they were "perfected goddesses."
Euryale was pictured as the "ideal girl", displaying a carefree demeanor, an overflowing smile, and the essence of purity in her actions and words. It is said that men will tremble in honor and swear to protect her at the cost of their lives should just their names pass from her lips. Unlike their younger sister who is an expert in fighting and disliked humans, she and Stheno perfect themselves as idols who liked humans, welcoming the men visiting the island, comforting them, and sending them on their adventure. Though her image on the surface seems to paint that as the very meaning of her existence, that is only to those observing them from afar. She is a devil who loves everything pretty and cute, freely and unconditionally. While she loves humans, it is not as "living beings", but rather in the way of toying with those she likes, embarrassing and driving them to ruin while watching them struggle. In reality, they truly hate men, while their sister is the one who bares them no ill will. They, loved by men, should be destined to be violated by them day after day. Though she despised her fate, Euryale had given up until Medusa became the one to protect them.
Stheno and Euryale appear briefly in Carnival Phantasm Episode 12.