Atalante, the Archer of the Red faction in Fate/Apocrypha, is a heroic spirit summoned from Greek mythology, known as the chaste huntress with unparalleled speed. Her background is defined by a deep wound of abandonment. Born a princess of Arcadia, her father, desiring a son, left her to die in the wilderness moments after her birth. She was saved only through the intervention of the goddess Artemis, who sent a she-bear to nurse and protect her. This traumatic origin forged her most defining trait: a fierce and absolute devotion to the protection of children. She was later found and raised by hunters, growing into a formidable warrior who joined the legendary Argonauts and was the first to draw blood from the Calydonian Boar. However, her life was also marked by a vow of chastity to Artemis, a promise she was forced to break when a suitor, Hippomenes, used three irresistible golden apples given by the goddess Aphrodite to win a footrace against her, an event that cemented her deep distrust of men.

In terms of personality, Atalante possesses a demeanor that is both feral and strangely archaic. Having been raised in the wild, her senses are as sharp as an animal's, and her green eyes hold a fierce, beast-like glint. She speaks in an old-fashioned manner and is characterized by her straightforward, honest nature, lacking the pretension of royalty despite her birth. Her worldview is rooted in the law of the wild; she sees taking what one needs to survive as natural and is not easily moved by the deaths of adults. This cold pragmatism, however, vanishes completely when a child is in peril. This contradiction stems from her own suffering; she wishes to repay the kindness she received by ensuring that no child ever experiences the loneliness and terror she felt when she was abandoned.

This singular, overwhelming motivation defines her actions throughout the Great Holy Grail War. Her wish upon the Holy Grail is not for power or glory, but for a world where every child can grow up surrounded by love. Initially summoned under a Master who was already a puppet of the priest Shirou Kotomine (Amakusa Shirou Tokisada), she serves the Red faction without strong loyalty to its leader, finding his goal of salvation compelling as it resonates with her own desires. While she distrusts schemers like her master, she cooperates to achieve her wish.

Atalante's key relationships are largely defined by conflict and tragic irony. She shares a notable dynamic with her Red faction comrade, Achilles (Red Rider). In life, she had been close to his father, Peleus, and her speed is considered by the centaur Chiron to be rivaled only by Achilles himself. She also forms a critical and ultimately destructive bond with Jeanne d'Arc (Ruler). Initially allies against a rampaging Berserker, their relationship sours during the battle with Black Assassin, Jack the Ripper. Jack is a grotesque amalgamation of the souls of abandoned, murdered children, a fact that strikes at the very core of Atalante's trauma. When Jeanne later uses her holy flag to purify and destroy Jack's lingering spirits, Atalante perceives it not as salvation but as the annihilation of the very children she had sworn to protect. This leads to a bitter and absolute enmity, as she brands Jeanne a false saint and vows to destroy her.

This marks the beginning of Atalante's tragic character development. Consumed by a vision of a grieving child and the curse of the defeated Assassin, her rationality crumbles under the weight of her own hatred and sorrow. In the final battle on the Hanging Gardens of Babylon, she is driven to unleash her forbidden Noble Phantasm, Agrius Metamorphosis. By donning the cursed pelt of the Calydonian Boar, she sacrifices her reason for immense power, transforming into a monstrous, berserk entity. In this state, she can no longer distinguish friend from foe. Her tragic end comes at the hands of Achilles, who, seeing the woman he respected reduced to a mindless beast, uses his own Noble Phantasm to deliver a mercy killing, destroying her Spirit Core and ending her rampage. Her story concludes not with the fulfillment of her wish, but with the tragic irony that her desire to protect children ultimately led to her own self-destruction.

As a Servant, Atalante wields several notable abilities. Her primary weapon is Tauropolos, the bow of heaven blessed by Artemis, which she uses to fire powerful shots. Her signature Noble Phantasm is Phoebus Catastrophe, the Complaint Message on the Arrow, a devastating anti-army attack. She fires an arrow as a plea to the gods Apollo and Artemis, who answer by raining down a torrent of magical light arrows upon her enemies. She also possesses skills like Crossing Arcadia, which allows her to leap over any obstacle on the battlefield, and Aesthetics of the Last Spurt, a technique reflecting her legendary footraces that lets her analyze an enemy's initial move and then counter faster than they can react. Her most dangerous ability, however, is her second Noble Phantasm, Agrius Metamorphosis: Boar of Divine Punishment. This cursed pelt, when worn, seals her bow but dramatically raises all her parameters and grants her power equivalent to A-rank Mad Enhancement. In exchange, she loses her sanity, transforming into a monstrous, bird-winged creature that can fire arrows woven from magical energy. Due to its self-destructive nature, its use is considered a last resort and a path to certain annihilation.