Illyasviel von Einzbern (Fate/kaleid)

Illyasviel von Einzbern (イリヤスフィール・フォン・アインツベルン) is the main protagonist of Fate/kaleid liner PRISMA☆ILLYA. She appears as Caster (キャスター), a Caster-class Servant able to be summoned by the Protagonist in the Grand Orders of Fate/Grand Order.

Background
Ilya 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.

Personality
Illya exhibits a cheerful and positive attitude; but unlike her counterpart, she is shy and easily flustered 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.

Fate/kaleid liner PRISMA☆ILLYA
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 Card that appears 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!
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 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 cast 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 co. collected. She defeats Luvia and take 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 propose 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.

Suddenly, from the rift of the worlds that Ea created, Angelica and Beatrice Flowerchild appears and took Miyu to their world. Illya and her friends are transferred to that world, too.

Fate/kaleid liner PRISMA☆ILLYA 3rei!!
In the parallel world, Illya met Tanaka and encounter 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 that was captured. Angelica appeared and Gilgamesh fights against her, 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 destroy 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 have an adventure in Ainsworth castle, where she met Beatrice and her obsession with Julian, also Rin and Luvia that are hypnotized to become Ainsworth maids. After escaping from Rin and Luvia's cleaning attacks, Illya found Sapphire and assume Kaleid Liner Sapphire form. She fights back, and succeeding to return to her body, until Angelica ambushed her and began to explain Ainsworths' true intentions.

Abilities
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 created a technique called Schneiden, a thin blade of magical energy with high cutting power and low cost. Illya was also able to learn how to fly, a difficult technique, without effort, because she believes that "all magical girls can fly".