Homunculus of the Einzbern family and later the wife of Kiritsugu. Carefree and innocent, she has both the elegance of a woman and the childishness of a kid. Still, she can understand well what Kiritsugu is going through even if she can't actual understand the meaning of his ideal.
Iris is artificially created by the Einzbern to serve as a vessel for the Holy Grail. Kiritsugu who was employed by the Einzbern to secure the Holy Grail gave Iris more than a purpose. Iris became Kiritsugu's lover and the mother of his child, Illyasviel who is artificially created using Kiritsugu's sperm and Iris's egg with sorcery. Iris was grateful to Kiritsugu who gave her love and a family and shown her that she is more than a puppet.
Irisviel von Einzbern is created by Gen Urobuchi and designed by Takashi Takeuchi as one of the main characters for the Fate Zero anime series. She originally appears in the visual Fate Zero, and makes her first anime debut in Fate Zero episode 1, Summoning the Ancient Heroes. She is voice by Sayaka Ohara in the Japanese version.
In her original design, she had antenna hair which was removed in her final design. She still retains her hairstyle that involves parting her hair down the middle.
Additionally, she appears in Fate/Kaleid Liner Prisma Illya - episode 9 "I'll End It Here" as a minor character. She makes subsequent appearances in the sequel series, Fate/kaleid liner Prisma Illya 2wei! as a supporting character. She makes another anime debut in a Type-Moon series called Carnival Phantasm.
Being a Homunculi, she has striking red eyes and white hair that extends past her nape and shoulders. For clothing, she wears her regal white dress when she is at the Einzbern mansion. In Fuyuki city, she usually wears a violet, long sleeved shirt with a white skirt.
She is a kind and sweet woman who is very outgoing and determined. She does not want others to have pity on her when she hides the fact her body is failing from Saber and Kiritsugu. She only tells Maiya who is not sympathetic. She often tries to patch things between Saber and Kiritsugu whose philosophies are stark opposites.
In season one of Fate/Zero, Irisviel and Kiritsugu welcome their daughter, Ilyasviel to the world. Upon obtaining the scabbard of Excalibur, Iri hopes that Kiritsugu can summon King Arthur of the Saber class. She and Kiritsugu are both shocked to see that King Arthur is a girl. Despite this shock, Iri seems to have a much closer bond to Saber than Saber does with Kiritsugu. Iri seems pleased to hear that Saber admires her wishes to save the world as she shares a very similar goal.
After arriving to Fuyuki City, Iris and Saber tour the city because this is Iris's first time outside Germany. After their tour of the city, she and Saber encounter Lancer at the docks. Observing the battle between Saber and Lancer, Iris then serves as Saber's healer during the period of the battle. When Lancer unleashes an attack using his Noble Phantas: Gae Buidhe, Saber is left with a wound on her left hand which leaves her unable to use it. Even Iri's healing fails to heal the wound. She and Saber then learn that Lancer's Gae Buidhe can cast wounds that cannot be healed. During the battle, Berserker assists Lancer against Saber, Saber asks Iris to retreat while she holds off Berserker and Lancer for as long as possible. Iris refuses to leave the battle and tells Saber to believe in Kiritsugu, who she knows is present at the scene and who has been observing the battle using his own tactics. Iris and Saber's battle ends when Rider threatens to assist Saber against Berserker and Lancer which causes the masters to pull back their servants.
Later on, Iri and Saber are driving on a road until they encounter Caster who believes that Saber is his long-lost love, Jeanne. Caster disappears from Iris and Saber's sight. Afterwards, Iri voices her concerns over Caster's motives in terms of sacrificing and killing children. Kiritsugu refuses to go after Caster despite his wife's protests. Kiritsugu confesses he would rather take Iri and their daughter and live somewhere peaceful. Then, Iri senses Caster and watches him through a crystal-ball. She is shocked to find him with more children in the forest. When Caster kills one of the children as a threat, Iris sends Saber to stop Caster. With Kayneth attacking the castle, Kiritsugu orders Maiya to get Iris away from the castle.
While Maiya and Iri manage to escape from Einzbern castle, they soon encounter Kirei Kotomine. Iri tells Maiya that they are going to confront him, and she orders Maiya to go by whatever means she needs to in order to defeat Kirei, not by what she was told to do by Kiritsugu. The two woman confront Kirei, but soon find they are outmatched by him. Kirei grabs Iri by the throat and begins to interrogate her about Kiritsugu. He orders her to tell him who ordered the two of them to attack me. When Iri does not respond, Kirei comes to the conclusion that they chose to fight them by their own means. Assassin arrives and informs him of Saber's approach. Kirei stabs Iri and departs, leaving her for dead. Saber finds Iri, who asks her about the whereabouts of Kirei. Saber takes responsibility for what happened to Iri, stating that if she had been quicker than Kirei would not have had the chance to stab her. Iri sits up, much to the amazement of Saber, and reveals that she healed herself. In truth, due to the fact she carries Avalon inside her, Iri's wound began to heal the moment Saber arrived.
While Maiya transports Iri and Saber to their new headquarters, Saber questions Iri due to the fact that Iri has allowed Saber to drive them to their new base of operations instead of driving herself. Saber eventually catches on to Iri's change in behavior when she realizes that she is avoiding touching anything. This leads to Iri confessing that her powers have weakened. This seems to concern Saber a lot. She proposes that Iri see a doctor, which is when Iri has to remind her that she is not a normal human being. Later on, Saber and Iris make a temporary alliance with Rider to stop Caster and his monster.
Iri observes as the battle with Rider, Saber and Lancer takes place against Caster's demon. While all methods of defeating the demon seem to fail, Kiritsugu manages to contact Waver and informs him of Saber's left hand, which houses her Noble Phantasm. He tells Waver to pass the message onto Lancer, who destroys his Gae Buidhe. Saber's wound instantly heals, and Iri watches on as she uses her Noble Phantasm - Excalibur to create a large blast of golden light which destroys Caster's demon and Caster.
Iri and Saber later arrive to the location where Lancer is. Lancer questions them on the whereabouts of Sola, who has gone missing. Iri and Saber are unaware that Kiritsugu and Maiya have kidnapped her. While Saber and Lancer engage in battle, Kiritsugu confronts Kayneth and threatens to shoot Sola. Kayneth is forced to agree to his terms, in which he uses his remaining command seal and orders Lancer to commit suicide much to the horror of Saber and Iri. Before Lancer disappears, he curses those around him. Iri can only stand in silence as Kayneth is shot by Maiya. Begging for Kiritsugu to kill him, Kiritsugu refuses. Saber puts an end to Kayneth's suffering before she confronts Kiritsugu over his actions. An argument between Saber and Kiritsugu rises, but Iri does not side with anyone. When Kiritsugu informs Iri of why he killed Kayneth and Lancer, Iri simply tells him that he should not be explaining his actions to her, but to Saber who needs to hear his words. After Kiritsugu leaves with Maiya, Iri collapses from exhaustion. Iri later wakes up to find Saber watching over her. She admits she feels guilty over the fact she has made Saber worry about her again. Saber dismisses her words and informs her that she only cares about the fact Iri is truly alright and safe. Iri is then informed by Maiya that Tokiomi has suggested an alliance. Iri agrees, but on the condition that Kirei is no longer allowed to participate in the Holy Grail war and that he leaves the city. Tokiomi agrees, and Iri leaves with Maiya. Afterwards, she confesses to Maiya that she is the vessel for the Holy Grail and so she will die near the end of the war. Maiya makes a promise to protect her from harm until the time comes.
Kiritsugu visits Iri, who hands Avalon back to him. She asks him to bring their daughter Ilya to Japan so she can explore it for herself after the war has ended. Maiya tells Kiritsugu that Saber has gone to fight Rider, and so Kiritsugu asks Maiya to protect Iri whilst he goes to kill Tokiomi. Iri and Maiya bond, with Maiya telling Iri about her childhood. This leads to Iri asking Maiya to live her life after the war is over. She also confesses that she hopes this will be the last Holy Grail war as she wants Ilya to be able to live a normal life. Very soon, Rider attacks Iri and Maiya at their location. Kiritsugu uses one of his command seals and orders Saber to get back to Maiya and Iri. There, Saber finds Maiya who is gravely wounded. Maiya tells her that Rider took Iri. Saber engages in a chase against Rider on her motorcycle. After she finally catches them, she finds that they do not have Iri. It is then revealed that Berserker was the one responsible for kidnapping Iri, and disguised himself as Rider. Berserker's master, Kariya, reveals that this is a part of Berserker's Noble Phantasm. Iri wakes up at Caster's lair and is interrogated about Kiritsugu by Kirei. After she tells him of Kiritsugu's wish; a world without conflict, Kirei kills her out of disappointment. Iri's soul then finds itself in the Holy Grail.