Illyasviel von Einzbern (イリヤスフィール・フォン・アインツベルン, Iriyasufīru fon Aintsuberun?) is the main protagonist of Fate/kaleid liner PRISMA☆ILLYA. She also appears as Caster (キャスター, Kyasutā?), a Caster-class Servant able to be summoned by Ritsuka Fujimaru in the Grand Orders of Fate/Grand Order.
Illya differs from her Fate/stay night counterpart in many different ways. She was born directly to be utilized in the fourth Fuyuki Holy Grail War, and she was given the knowledge needed at birth. Her father and mother, Kiritsugu and Irisviel, had been discussing completely abandoning the ritual and the Einzbern family, and Irisviel was given the final choice. They decided when Ilya was eight months old, and sealed her magical abilities and her memories up until that point. They remained within her as a separate personality, Kuro, that continued to accrue the same memories as her.
She was brought to Fuyuki from the Einzbern castle and raised as a normal child along with her adopted brother, Shirou. Their parents were away for long periods of time, so they were left with Sella and Leysritt much of the time. She had a normal life for ten years without any knowledge of her background, and had no idea about her parents' activities.
She has basically the same appearance as her Fate/stay night counterpart, even though here she is younger. Being originally an Einzbern homunculi, Illyasviel has crimson eyes and long white hair just like her mother, Irisviel. She wears many casual outfits but the more recognizable ones are her regular school uniform, summer school uniform and her pink Magical Girl outfit after contracting with Magical Ruby. While using Magical Sapphire, she wears a purple outfit, a little bit different from Miyu's.
In the Zwei Form where she wields both Magical Ruby and Magical Sapphire, her outfit changes to a purplish color with and she obtains cosmic-like wings. As a Card User she is able to install Class Cards and to obtain outfits and equipment of various Heroic Spirits. She only becomes able to do it by herself during her first fight with Beatrice Flowerchild.
Illya exhibits a cheerful and positive attitude; but unlike her counterpart, she is shy, easily flustered, and more innocent at the beginning. In her first fight, she is shown to be agile but rather cowardly. Also, Illya is an ardent fan of anime, much to Sella's disappointment. She secretly harbors feelings for her brother, Shirou, something that Ruby highlighted much to her embarrassment.
When interacting with her friends at school, she shares a dynamic relationship with them where she usually acts as the voice of reason, a role that is very much like a Tsukkomi (a person who throws punchlines). This is particularly expressed when it comes to suggestively lewd or comedically immoral situations.
As the series progresses, Illya matures into a strong individual who's willing to face overwhelming odds for what she cares about while also maintaining her innocent nature and strong morals. This is proven when Illya also wants to protect everyone, especially her friends. It is shown as Illya proclaims that she will help Miyu and her world, even though Julian stated that it is almost impossible.
This characterizes the immeasurable amount of kindness Illya possesses that she is considered a natural genius in becoming friends with her enemies. 
Despite her growth in maturity, she still holds behaviors fitting of her age such as childish tempers, trying to act mature, and being stubborn towards things she dislikes. Like all young girls her age she adores cute things like animals and stuffed toys. In stark contrast to her original version, she really likes cats.
Fate/kaleid liner PRISMA☆ILLYAEdit
Illya lives as a normal 10-year-old girl with her family in Fuyuki City, not knowing her true nature as a Grail conduit. One day, when she's having a bath, she met Magical Ruby and accidentally made a contract. Rin then confronts her to take Ruby back, but Ruby refuses to return to Rin. So, Rin appoints Illya as her "servant", to collect the Class Cards that appeared in Fuyuki.
In her first battle, she is cornered by the Rider Class Card manifestation until Miyu Edelfelt helped her. The next day, Miyu transferred to Illya's elementary school and instantly grabs attention with her talents. Meanwhile, Magical Sapphire explains Miyu's situation.
Her next enemy is the manifestation of the Caster Class Card. But, Illya, with Rin, Miyu, and Luvia got defeated very quickly. The only way to defeat Caster is to bypass her magic circle in the sky, so they must fly. Illya can fly easily because of her magical girl imagination, but Miyu can't. So, Illya helps Miyu to learn to fly. In the end, Miyu still could not fly, but they could defeat Caster with two magical girls' teamwork.
Suddenly, the manifestation of Saber Class Card appears and instantly defeat Rin and Luvia. Illya and Miyu then make a plan to defeat it: give the Kaleidosticks to the more experienced magus. Rin and Luvia, in their Kaleid forms seemed to win until Saber unleashes her black Excalibur. At this moment, Illya's seal of her Grail power cracked and she unconsciously Installed Archer Class Card. With Archer's abilities, she defeats Saber.
The next day, Illya comes down with fever and Miyu pays her a visit. They deepen their friendship, while Ruby and Sapphire discuss Illya's true power.
In the fight against Assassin's Class Card manifestations, Illya unknowingly unleashed a devastating magical attack that demolished the enemies and almost killing Miyu, Rin, and Luvia. Scared of her dangerous power, she resigns from her duty as a magical girl.
With Illya leaving the team, Miyu confronts Berserker Class Card alone, and she is cornered. Meanwhile, Irisviel comes back and talks with Illya about life when she is away. Illya comes to realize her friendship with Miyu and decided to help her. Miyu Installed Saber Class Card to fight toe-to-toe with Berserker until God Hand kicks in, and at this time Illya came to help. Together, they defeat Berserker, and with his card, the Class Card collection is completed.
Fate/kaleid liner PRISMA☆ILLYA 2wei!Edit
Sometimes later, Rin and Luvia kidnapped Illya and Miyu to perform the next task from Zelretch, to stabilize the flow of mana in Fuyuki city. They came to the cave beneath Ryuudo temple and seemingly succeeding their task, but the cave collapsed. Illya, using her Grail power, installed the Archer Class Card again to save the party with Rho Aias. Suddenly, Kuro appears from within Illya and escaped.
The next day, Kuro attacks Illya and Miyu. She explains that her purpose is to kill Illya and take her place, and defeat the both of them before Illya shred her clothes. Rin and Luvia then organize a plan to capture Kuro, using Illya as a bait. They ultimately succeed, and Rin casts a pain-sharing curse to Kuro so she can't harms Illya anymore.
Kuro then transferred to Illya's school and kissing most of Illya's close friend (and Taiga), causing Illya to confronts her again. After dueling at a ball game, Illya protest to Kuro that she want her life to returns to normal, making Kuro fighting against Illya and Miyu again, because she doesn't want to be forgotten. In the fight, suddenly Irisviel appears and knocking both Illya and Kuro out. She then takes them to Luvia's bath. Kuro asked Irisviel about her true nature, apparently she is Illya's part of memory that sealed simultaneously with Illya's Grail conduit. She then began to disintegrating, but Illya gave her mana so that Kuro can still exists. Irisviel then introduce Kuro as Illya's distant cousin, so she stayed within Einzbern household. Illya and Kuro's relationship then become not unlike real sisters.
One day, Bazett appears to seize the Class Cards that Illya and the others collected. She defeats Luvia and her butler and later takes Illya, Miyu, and Kuro head-on, until Rin appears and use the same pain-sharing curse that Illya and Kuro have to her. Rin also told Bazett about the 8th Class Card and proposes to cooperate with her. After that, Bazett retreats.
After Illya, Miyu, and Kuro's birthday party at the beach, they confront the 8th Class Card with Bazett. With great teamwork, they seemingly win against the enemy until he draws Ea and destroy the Mirror World, escaping to the real world. Caren appears and explains that the 8th Class Card is going to Mount Ryuudo. Illya and Miyu confront the enemy, until Illya unknowingly pushes the manifestation, Gilgamesh out from its darkening form.
Gilgamesh explains that he came from Holy Grail War at a parallel world, Miyu's homeworld and that Miyu is the Holy Grail of that world. Miyu then surrendered herself to Gilgamesh. To take Miyu back, Illya borrowed Sapphire's power to became Kaleid Liner Zwei Form. She then defeat Gilgamesh and saved Miyu.
Fate/kaleid liner PRISMA☆ILLYA 3rei!!Edit
In the parallel world, Illya met Tanaka and encounters Beatrice again, until she is called by the Ainsworths. Illya and Tanaka then visit Kirei's ramen shop, where they met Gilgamesh again. He agreed to help fighting against Ainsworths, because "it is interesting".
At Ainsworth's castle, the party met parallel world Shirou who was captured. Angelica appeared and Gilgamesh fights against her announcing that she was his goal, whilst Illya and Tanaka escaped. Beatrice intercepts and wallops them, until Illya reunited with Ruby and fights back with Caster Install. Before Beatrice and Angelica took them seriously, they escaped. Kuro and Bazett then appear to assist them in escaping.
Using Illya's primary school as team's headquarters, Kuro then confronts Illya to know her true feelings about their situation. Illya defeat Kuro with Lancer Install, and confirmed that she will help Miyu whatever it takes. Bazett then spreads a rune bounded field to warns them against intruders, but Erika can bypass them because she holds no ill intent. After that, Darius Ainsworth came to pick up Erika, and in the process, hold off against the attack of Illya, Kuro, and Bazett with his unknown Noble Phantasms. After Tanaka destroyed his barrier Noble Phantasm, he retreated.
At night, Angelica used her hypnotism to capture Illya and insert her soul into a bear stuffed toy. Illya then has an adventure in Ainsworth castle, where she met Beatrice discovered her obsession with Julian, and also Rin and Luvia who were hypnotized to become Ainsworth maids. After escaping from Rin and Luvia's cleaning attacks, Illya finds Sapphire and assumes Kaleid Liner Sapphire form. She fights back, and succeeds returning to her body, until Angelica ambushed her and began to explain the Ainsworths' true intentions to save the desperate world by using Miyu. Suddenly, Kuro comes to the rescue, stating that she would still choose Miyu over the world, which confuses Illya. After a battle between Angelica and Kuro, Illya finally exclaims that she would try to rescue both Miyu and the world. Then, Kuro gives Illya all of her cards, and pairing Sapphire with Ruby, Gilgamesh, and Bazett which comes and hitting Luvia and Rin's seal, so their minds could return to their bodies. After that, Kuro destroys the Central Tower and Gilgamesh rushes to rescue Miyu's older brother.
After that, Illya flies in to rescue Miyu. Darius then tries to incapacitate Illya by using Crown Undertaker and Ninth Prayer, but Illya uses Saber Install, foiling those two Noble Phantasms. Illya then strikes at Darius with Saber's Sword, which has no effect. Illya then uses Rule Breaker via installing Caster's card to stab Darius' chest which successfully harms him allowing his facade to gradually fade, and makes him relocate the castle. Beatrice appears and attacks Illya, but Illya throws Sapphire to Miyu, and finally they reunite.
After relocating the Castle, Darius' Facade was completely destroyed, and revealing that he is actually Julian Ainsworth. Claiming he has to complete his Legend, he personally warns Illya not to intervene with his plans, and destroys Illya's Caster Card. Meanwhile, after the Pandora Box spawn endless army of Mud, he asks Miyu to return, which suddenly Illya interferes and asks Miyu not to return to the Ainsworths, which make Julian orders his Mud army to fire arrows at Luvia, Rin and Bazett. Then Emiya Shirou appears, blocking the arrows with Rho Aias and helps them to fight the Ainsworths. Together with Kuro, they defeat Angelica even after she accelerated the Noble Phantasms to an unreactable speed. Following her defeat, Shirou rushes to Julian brandishing Kanshou and Bakuya.
Sakura suddenly appear as the last line of defence for Julian when Shirou attacks him. Seemingly appearing from the mud below Julian's feet, she attacks using the power of the Berserker, Lancelot. Catching him by surprise, she severely wounds him. Stating that she had been waiting for him a very long time, she is attacked from behind by Miyu, who uses the Gilgamesh class card to attack. Despite he onslaught of weapons Miyu uses, Sakura is able to take control of them. Before Miyu can launch into another barrage, her personality starts to be overtaken by that of her own class card, and Julian interrupts, taking the Archer card from her.
No longer possessing that power, Sakura proves overwhelming, nearly killing Miyu before Julian once again intervenes. Using the power of his Assassin class card, Julian restrains Sakura and Miyu and, taking Shirou's image, convinces her to halt her assault. She is last seen being dragged back into the mud by the Assassin's Noble Phantasm.
After that, Julian is confronted by Gilgamesh, who tells him that his wish can't come true unless he has two Holy Grails to accomplish it. Gilgamesh then notices Erica, and after hearing her, he notices something, laughs, and telling the Ainsworths he's going to enjoy watching it, and disappears from sight when Beatrice swings Mjolnir at him.
While in the abandoned school, Tanaka reawakened. Illya is struggling defending Rin who tries to heal Emiya Shirou's wound. She charges Excalibur with prana and , and succeeded to blow away a lot of the Mud creatures. But her mana is depleted because of that, and Julian simply stated that the Mud Creatures will reform and endlessly swarm them. Tanaka, from the distance throws her hand, revealed to be a Sword, to Illya. The sword proves to be Lethal against the Mud and Pandora Box. Illya succeeded in stopping Erica and the Pandora Box, and proclaimed to Julian that this is her victory. Julian then permits Beatrice have two swings of Mjolnir, which she gladly does. But Illya and Miyu survived thanks to Shirou's Rho Aias. As this occurred, Rin successfully heals Shirou with the gem on her necklace found by Bazett.
After that, the glowing hot red sword turned into a arm/hand which begins to tease Illya and chasing her and unbeknownst to Illya, it was actually Tanaka's hand. Shirou then invited them to his house, which all agrees, even Angelica, which has been rescued by Illya earlier. Upon arriving at the house, all members except for Shirou and Miyu were surprised at the immense size of the size, saying that it was comparable to a mansion. Illya and Kuro took a bath, and discusses Miyu's identity, while Tanaka's hand comes and touch them. Surprised, they threw the hand. That hand reveals that it is Tanaka's, which shows them they haven't picked up Tanaka yet from the school. After that, Illya and the others present at the Living room, preparing to hear Miyu and Shirou's story about them.
It was from there, Illya learns of Miyu's and Shirou's past from how they met, how Miyu becomes Shirou's actual little sister, Matou Sakura's death, Julian, the Ainsworths Holy Grail War, Shiro's involvment in the war, the Archer Card's identity, and how Miyu came to Illya's world. The revelations brought Illya to tears where she then told Shirou what happened to Miyu in her own world.
Magical Girl Diaries ~Prisma Corps~Edit
While she wields the Kaleidostick, Magical Ruby, she is granted A~Rank Magical Barrier, Physical Protection, Accelerated Healing and Increased strength. Due to her free spirited nature, Illya was also able to learn how to fly, a difficult technique, without effort, because she believes that "all magical girls can fly". This level of imagination can even allow her to move and speak in the body of a stuffed animal that her mind was transfered to.
As a Lesser Grail, Illya possesses unnaturally high magical output, though it is greatly reduced after Chloe was created. To compensate the loss in output, she devised ways to refine the shape and utilization of her attacks. An example is a technique called Schneiden, a thin blade of magical energy with high cutting power and low cost. Another example is how she has demonstrated a clever usage of her magical barriers. She created a barrier technique called Pyramid where she deployed a forward physical shield in the shape of a pyramid and used her barriers as forms of restraints.
When wielding both Magical Ruby and Magical Sapphire, she is able to enter a new powerful form called Zwei Form. This transformation grants her an immeasurable boost in her magical girl abilities that makes her a match against Gil and Gilgamesh together. However, this takes an extreme toll on her body as it turns every part of her body, primarily the muscular, nervous, vascular and lymphatic tissues, into a Magic Circuit. Ruby points that such a form can potientially cease all her body functions, killing her which makes it a last resort.
Through the Class Cards, she is able to include and install them, granting her the abilities of a Heroic Spirit.
She posseses a strong mental fortitude that makes her immune to brainwashing and can protect her memories and emotions in a conceptual space that Chloe left when the two seperated. This strong will has also made her more resistant against Berserker's Mad Enhancement.
Because of her kind nature and ability in seeing the good in others, she has the notable skill in making enemies into her allies. Examples include Miyu, Chloe, Bazett, Gil, and Angelica.
 Fate/kaleid liner PRISMA☆ILLYA 3rei Volume 2, p.97 - Saber
Excalibur: Promised Sword of Victory: A++
The pinnacle of the "Holy Sword" category. Owner's magical energy is converted to light, increasing it's momentum via convergence and acceleration to it's utmost limits before releasing it in one slash. It is said to reach the class of Divine Spirits. Because it is an amplifier that converts the owner's magical energy, when blackened Saber used this Holy Sword, it was black as well.
Obtains King of Knights Artoria Pendragon's abilities. Britian's legendary King Arthur who pulled out the selection sword. Attack, Defense, Reactions, Magical Ability, and Noble Phantasm are all lend to her being called the most excellent Heroic Spirit. A Heroic Spirit with a serious personality as straight as an arrow, however, personality-wise there are many sides to her as well. The figure the time Ilya uses her is not in the role of a King but rather the strong expression of her Princes Knight side.
Invisible Air: Bounded Field of the Wind King: C
The wind bounded field that covers the Holy Sword in many layers. Usually, it is used to hide the excessively famous holy sword's shape by changing the air's refractive index. However this is no such need in this work so the Holy Sword is normally in it's released state.
「聖剣」というカテゴリにおける頂点。所有者の魔力を光に変換し、収束・加速させ運動量を極限まで増大して 放たれる究極の一閃は、神霊クラスにも手が届くと言われる。所有者の魔力を変換する増幅器であるため、黒化 したセイバーが振るっていた時はこの聖剣もまた黒く変色していた。
夢幻召喚 - The original manga volume version included Rider's description by mistake, and was later corrected.
- ↑ 2.0 2.1 Fate/kaleid liner PRISMA☆ILLYA 3rei!! Chapter 42
- ↑ Fate/kaleid liner PRISMA☆ILLYA Volume 1, Chapter 01
- ↑ Fate/kaleid liner PRISMA☆ILLYA 2wei! - Chapter 10
- ↑ Fate/kaleid liner PRISMA☆ILLYA 2wei! - Chapter 14
- ↑ Fate/kaleid liner PRISMA☆ILLYA 2wei! - Chapter 26
- ↑ Fate/kaleid liner PRISMA☆ILLYA 2wei! - Chapter 27
- ↑ Fate/kaleid liner PRISMA☆ILLYA 3rei!! Chapter 5
- ↑ Fate/kaleid liner PRISMA☆ILLYA 3rei!! Chapter 13