She is the wife of Kiritsugu Emiya and the mother of Illyasviel von Einzbern. For the Fourth War, Jubstacheit von Einzbern decided to create a humanoid shape as the Grail consultation drawing in a child’s life that has a consciousness and can be independent to defend itself from harm.
He used the archetype base of Justeaze Lizrich von Einzbern to create Irisviel, thus referred to as a Justeaze-late model. Kiritsugu Emiya first met Irisviel when she was created inside a tube. Through his interactions with her, he found her to be useless and Kiritsugu expressed his frustration to Jubstacheit regarding Irisviel’s lack of understanding towards protecting herself and interacting in society. In response, Jubstacheit decided to prove Irisviel’s durability by casting her into the wastes of the Einzbern forests. Because the plan of conceiving Illyasviel was decided after Irisviel was coined, her pregnancy of Illyasviel was not much of a natural development since it was an additional role imposed onto her that she originally was not supposed to have. An exception among Einzbern homunculi whose functions are determined when they are designed.
It was due to Jubstacheit’s judgement that it would be more efficient to nurse a child rather than produce a homunculus. Made to be a puppet with no desires, she managed to find happiness in her existence when she gave birth to Illyasviel. Furthermore, nine years is a long time to maintain a relationship with a human. Before her, there were no precedents of an Einzbern-made homunculus with such a colorful and eccentric personality. She was the first Einzbern homunculus to be treated like a human being and learn human emotions to such an extent. As a homunculus of the Einzbern, Irisviel possesses a genetic resemblance to her ancestor, Justeaze Lizrich von Einzbern, who formed the core of the Holy Grail when the Holy Grail Wars began. Her long silver hair and red eyes are distinctive traits of Einzbern homunculi, such that Tohsaka Tokiomi recognizes right away that she is a member of the Einzbern family.