Sola-Ui is described as a woman who gives off the feeling being an extremely cold and possessing a severe and temperamental sense of authority. She behaves according to her background as a high-class woman born as a prestigious aristocrat, though she is also a person who is sentimental.
Cruel and careless, Sola-Ui is both devious and clever, often taking advantage of circumstances to get what she wants. She has no affection for Kayneth and does not get along with him well, deriding him harshly as a coward for not confronting his enemies openly. In contrast, she has no qualms about developing feelings towards Lancer and deferring to him when he defends Kayneth's behavior.
She is engaged to Kayneth El-Melloi Archibald as a result of a strategic marriage arrangement and the decision of her family to entrust their crest to her older brother, Bram Nuada-Re Sophia-Ri instead. Because her brother did not succeed as a mage, there is increasing pressure from her family to marry Lord El-Melloi.
Sola was designed to be a girl with a strong nose bridge, so Takashi Takeuchi designed it to be straight. He wanted to do something different with her costume, but it turned into a simple blouse and ribbon design after he simplified it a great deal. One of the comments from Gen Urobuchi was "Isn't she too cute?" Her cuteness caused Nasu to "come down with a strange disease", and he turned down Takeuchi's idea to make her more lively. Urobuchi thinks team Lancer would fit better into a comedy in contrast to the misfortunes they suffer in the story, and wondered if he should have given her longer scenes after becoming Lancer's Master.
Fate/ZeroEditSola-Ui is Kayneth's fiancée and apparently does not get along with him. While Kayneth acts as Lancer's Master, Sola-Ui maintains the materialization energy for the Servant. Her first appearance occurs in the second novel of the series, after the melee battle between the Servants.
She openly calls him a coward for not facing the other Masters face-to-face and criticizes his strategy when commanding Lancer against the other Servants. However, she is quickly chastised by Lancer, who stops her from arguing any further with Kayneth. As a result, he suspects that she may be developing affections for the Servant. Before the issue is addressed, Kayneth's stronghold in the Fuyuki Hyatt Hotel is attacked by Kiritsugu Emiya and Maiya Hisau.
After several confrontations with Kiritsugu, Kayneth is eventually severely injured. Sola-Ui coerces him into surrendering his command seals to her, under the threat of killing him if he refuses. He reluctantly agrees, given the extent of his physical injuries. Sola-Ui, now Lancer's Master, is disappointed that Lancer only sees her as a proxy to Kayneth because of his sense of honour and his guilt towards abandoning his previous Master when he was alive because of a woman.
Sola-Ui later witnesses the battle between Caster and the other Servants from a distance, after Lancer refuses to take her into battle. During the battle, she is suddenly attacked and knocked unconscious by Hisau Maiya. Maiya chops off one of Sola-Ui's arms, the one which carries the command mantra of Lancer, and then takes the woman as bait for Kiritsugu to use against Kayneth. The anime adaption depicts Sola-Ui's arm being cut off before Maiya renders her unconscious, forcing Sola-Ui to endure the horror of being unable to use any Command Spells to summon Lancer or forcing him to reciprocate her love.
She proves to be effective collateral against Kayneth; during Lancer and Saber's fight, Kiritsugu appears before El-Melloi holding Sola-Ui captive at gunpoint. Kayneth agrees to a mage's contract, an unbreakable agreement between mages at the cost of permanently being unable to use sorcery, where Kiritsugu agrees not to harm either Kayneth or Sola-Ui on the condition that Kayneth forces Lancer to kill himself. In the sound drama, she was still conscious when she saw Lancer commit suicide and was devasted when Lancer dies but in the novel and anime she was unconscious. She and Kayneth are shot by Maiya soon after and Sola-Ui dies of gunshot wounds.
Sola-Ui is a descendant of the Sophia-Ri family and possesses considerably higher numbers of magical circuits than an average person. While her status as a magus is low because her family entrusted their family crest to her older brother, her bloodline is prestigious enough that her match with Kayneth is seen as definite assurance that the next generation will exceed their ancestors.
Though few of her skills as seen, Sola-Ui was able to heal Kayneth's wounds after he was almost killed, but unable to restore his magic. She has sufficient mana to maintain the materialization energy for Lancer, even after losing her arm containing the command seals for the Servant and enduring the pain to remain alive afterward, in spite of severe blood loss and only receiving basic first aid.