Ten years ago, in the aftermath of the Fourth Holy Grail War, Illya had a vision of her mother Irisviel "Iri" von Einzbern, who claimed her husband and Illya's father, a participant in the war, betrayed them by refusing to accept the Holy Grail when it presented itself to him. At first, she refused to believe it, but realized the truth when her father did not return home. As time passed, she stumbled upon a pool in her home, containing numerous homunculi that were created to serve Illya's purpose, only to fail in their missions. Realizing she is also a homunculus from their dying messages, Illya became disillusioned with her life. Later on, she met Leysritt and Sella, who assisted her in summoning Berserker. However, she initially did not want him, resolving to participate and win the Holy Grail War by herself. During the final test of her link ritual, she was separated from Berserker and lost her way in the nearby snowy woods. A pack of wolves attacked her, but she was rescued by Berserker. She realized that he protected her of his own free will afterwards. In the present day, Illya and Berserker continue their battle against Gilgamesh as Shirou and Rin arrive to witness the event. Gilgamesh reveals Berserker's God Hand gives him twelve lives, one for each of the Labours of Heracles, and steadily depletes them with his countless Noble Phantasms from Gate of Babylon. As the battle reaches the main entrance, Gilgamesh eventually restrains Berserker using another Noble Phantasm, Enkidu, a set of unbreakable binding chains. Gilgamesh impales Berserker with a large spear, then blinds Illya and stabs her with a sword. As she crawls to Berserker's side, he breaks the chains and makes one last attempt to strike Gilgamesh, only to be killed. Shirou tries to intervene, but Illya dies in comfort, believing Berserker is still at her side.