Illyasviel von Einzbern, commonly called Illya, is a homunculus crafted by the Einzbern family to act as the Holy Grail vessel in the fourth Fuyuki Holy Grail War. Her parents, Kiritsugu Emiya and Irisviel von Einzbern, abandoned the ritual when she was eight months old, sealing her war memories and magical powers. These sealed memories formed a distinct personality, Kuro, who accumulated experiences alongside Illya. Raised in Fuyuki City under the care of maids Sella and Leysritt, alongside her adopted brother Shirou Emiya, Illya lived as an ordinary elementary school student. Her frequently traveling parents allowed her a relatively normal childhood, separate from her magical heritage. Physically, she possesses long silver hair, red eyes, and the youthful appearance typical of Einzbern homunculi. Initially, Illya combines cheerfulness with timidity, contrasting with her solitary counterparts in other timelines. Easily flustered, she enjoys anime, cute animals, and has a fascination with maid outfits. Her early magical girl activities reveal reluctance in combat and cowardice, though she displays agility. Across series seasons and films, she matures significantly, developing unwavering determination to protect friends and confront overwhelming threats. This growth includes facing impossible odds, such as vowing to save both Miyu Edelfelt and a dying parallel world. Key relationships define her character. She forms a deep bond with Miyu Edelfelt, her initial rival as another magical girl wielding the Kaleidostick Sapphire. Their dynamic evolves into a close partnership, marked by Illya's fervent dedication to their shared battles and daily life. Kuro (Chloe von Einzbern), her manifested alternate personality, begins as an adversary but integrates into the Einzbern household as a sister figure, leading to playful rivalries and mutual reliance. Interactions with characters like Rin Tohsaka and Luvia Edelfelt often position Illya as a voice of reason in morally ambiguous or comedic situations. Contracted with the sentient Kaleidostick Ruby, Illya gains transformative abilities, adopting a pink-themed outfit and wielding magical attacks. She later temporarily uses Sapphire, resulting in a purple costume variant. Her combat prowess expands through Class Card installations, enabling temporary channeling of Heroic Spirits. Her Saber-class installation accesses a "Princess Knight" aspect. In critical battles, she combines Ruby and Sapphire into the Zwei Form, gaining cosmic-style wings and enhanced power, pivotal against adversaries like the manifested Caster under Fuyuki Bridge and Gilgamesh in the eighth Class Card conflict. In *Licht - The Nameless Girl*, Illya confronts Julian Ainsworth's plan to sacrifice Miyu to save a dying world using the Holy Grail. The film depicts her resolve to find a solution preserving both Miyu's life and the world, positioning her as the central force challenging the Ainsworth family's methods. Her journey culminates in this high-stakes conflict, emphasizing her evolution from a reluctant magical girl to a protector defying fate.