Furina

In the medical and mystical lore of Genshin Impact, Collei is a mortal human native to Sumeru whose body once served as a battleground between two deadly supernatural afflictions: congenital Eleazar and injected Archon Residue. Eleazar—the Sumeru-specific manifestation of Irminsul's forbidden knowledge corruption—caused dark, hardened scales and progressive nerve numbness across her limbs from infancy. To make matters worse, Fatui experimenters under Barnabas and Dottore infused her body with the wrathful remains of dead gods (Archon Residue), granting her cursed black serpent flames at the cost of excruciating agony.

After General Mahamatra Cyno sealed the dormant Archon Residue inside her in Mondstadt and Lesser Lord Kusanali later purified Irminsul's forbidden knowledge at the climax of the Sumeru Archon Quest, Collei was finally cured of Eleazar completely. Her constellation, Leptailurus Cervarius (the Serval Cat), symbolizes her resilient wilderness instincts and her handmade cat plush doll, Cuilein-Anbar.

Born in Sumeru with severe Eleazar, young Collei was handed over by her desperate mother to a Fatui operative named Barnabas, who promised that the 'seer' Il Dottore could cure the terminal disease. Instead of receiving humane care, the child was subjected to horrific human experimentation inside a Fatui laboratory, where Archon Residue was forced into her bloodstream to suppress Eleazar's progression. Although she survived where countless other test subjects perished, the trauma left her distrustful, illiterate, and haunted by the black flames coiled inside her soul.

After escaping the destroyed laboratory and wandering across Teyvat as a fugitive, Collei arrived at the gates of Mondstadt during the Ludi Harpastum festival (chronicled in the official Genshin Impact prequel manga). Although her fear and awakening Archon Residue initially drove her into conflict with the Knights of Favonius, Outrider Amber refused to give up on her, showing Collei unconditional friendship and kindness. With the help of Amber, Diluc, Kaeya, Lisa, and visiting Sumeru scholar Cyno, the rogue Fatui experimenter Barnabas was defeated and Cyno sealed the Archon Residue inside Collei's body.

Returning to Sumeru with Cyno, Collei was entrusted to the care of Forest Watcher Tighnari in Gandharva Ville. Later, while rescuing a lost child from ferocious beasts in a stormy rainforest canyon without hesitating over her own frailty, Collei earned a glowing Dendro Vision of her very own.