In 5th Century England, a Magus named Merlin arranged for King Uther Pendragon to sleep with Igraine, the wife of his enemy Gorlois. Merlin did so following a prophecy that stated this would lead to the birth of a legendary hero who would become king and save this dying country from ruin. However the child born was not a boy, but a girl, which brought despair to the king who could not make her his successor, but Merlin was not concerned, as he had faith she would still fulfill that destiny regardless of her gender.
The child, named Arturia Pendragon, was taken to the family of Sir Ector to be raised as their child. Nobody knows why, but even looking at Arturia, people could tell there was something wrong with her. She was a kind, compassionate, and gentle person, but she never seemed too happy for herself and it seemed like she never did anything for fun, almost as if there were some kind of mental distortion where she did not value her own life. She could only gain happiness from seeing others smile, unable to smile for herself. No one knows why she was like this, whether she was like this from birth or something traumatic had happened, though it is believed by many who knew her that being born into this period known as The Dark Ages, and seeing all the misery of those around her, is a large part of it. From as far back as she can remember, she looked at the suffering around her wishing to bring an end to it. She believed if she worked and trained hard enough, she could become a king that could save this country, and swore to hold the sword without ever being asked to. She spent most of her life up to the age of 16 training and preparing for that day, almost as if she felt it was the only thing she existed for. Day and night she trained to become stronger than anyone and became a master of swordsmanship.
When she was 16, an event was held to select the king. A naked sword was stuck in a stone, and only the one who could pull it out would be crowned king. Nobody could pull it so the knights turned to jousting to select their king. With the area around the sword empty, Arturia approached it and went to grab it, but Merlin stopped her, warning she would no longer be human after this, and that she would die a miserable death resented by all humanity. He showed her a vision of herself alone on a hill of swords dying, but she only nodded back, saying the smiling faces in that vision were worth that price. Without even a slight hesitation, she pulled the sword, discarding her life, and most of all, her humanity. Becoming a king meant no longer being human as the responsibilities placed upon her would require someone without human emotions to fulfill without flaw. She only wanted to protect everyone, but had to throw away the emotion of wanting to protect them to do so.
From that moment on she was like a machine, completely stoic and without doubt. With the help of Merlin’s magic, she was viewed as a male by those around her and would go by King Arthur. Those around her looked down on her as a small child, but were forced to follow her because she pulled the sword out, in order to win their hearts she had to show results of perfection that made them accept there was no-one better, but this meant there was no room for the human being known as Arturia, so she became isolated by her own kingship, not even spoken to by any of her knights if it wasn’t about important business.
For 10 years and 12 battles she ran through defeating invading armies, delivering hope to her country, and rallying divided kingdoms together and uniting them. Her efforts were not without sacrifice and she would end up taking more lives, including her own civilians, than any other knight in existence. Were there any guilt, she did not show it, suppressing herself completely to make what truly was the right choice, if not the easy one. And after many years of flawless kingship, one knight murmured that she did not understand human feelings and left Camelot. Nobody wished for her to be human yet they turned away from her for not having human feelings. The one time she did act with humanity it lead to her downfall, she noticed her queen and Lancelot were together and kept the secret to herself, only for it to be exposed later by her most hated enemy, Morgan Le’Fay. She hated Arturia for becoming king instead of her and made many attempts to undo King Arthur’s rule, including the theft of the sheath of Excalibur and the construction of a clone homunculus of Arturia known as Mordred. Mordred seized the throne when Arturia was on an expedition and Arutira had to return with her tired troops and slash away at the cities and knights she once protected and fought for. This battle, The Battle of Camlann, ended with King Arthur and Mordred face to face in personal combat, and the king victorious, but at the price of Mordred dealing a fatal blow to her. She lay there on a hill of swords, dying, and she realized this was the end that had been foretold, as she let go of the sword, her King Arthur persona vanished at the completion of her duty, but Arturia was not able to accept this, and tried to continue to act as the king she once was. Wondering how it could have ended like this, she concludes it was because she was not good enough, that she was picked by mistake, and that there was another hero who should have pulled the sword.
Laying there, she wished for the Holy Grail to go back and redo the selection, so she made a contract with the world to obtain it before dying on the condition that she becomes a Counter Guardian after dying. At that moment, Arturia was frozen in time and shortly thereafter summoned as a Saber class Servant into the fourth Heaven’s Feel in the very late 20th Century. Arturia’s time in the 4th ritual was unpleasant to say the least. Her kingship was talked down to her by a rival, her Master would not speak to her, and she discovered that Lancelot, one of her few friends, had become a Berserker, and learned it was because she did not punish him for loving Guinevere when she initially found out, which only made Arturia feel more responsible for the failure of her kingdom. Finally, Kiritsugu Emiya, her Master, ordered her to destroy the Holy Grail when it was right in front of her and never explained why he did so.
As she returned to the hill of swords, she was overwhelmed in despair until a light shined over her, she was called again, even though she destroyed it last time. When she answered the call this time, she was summoned as Saber into the fifth Heaven’s Feel one decade after the fourth. Her Master was a boy named Shirou Emiya, the adopted son of Kiritsugu. Despite having many reasons to not trust the son of the man who betrayed her, she felt some unexplainable need to protect him from the moment she saw him, not just as a Servant, but in general. She chose to suppress this emotion like all others and acted professional as his Servant.
Shirou was not an experienced Master, he did not even understand what this ritual was or what Servants were. Saber still agreed to be his Servant despite this and fought many battles to protect him. Just as Saber’s mind was distorted and lacked value for her own life, Shirou’s was the same, while he was not yet as skilled as her, he would still put his own life in danger to protect hers. Unlike everyone else who saw her only for the warrior on the surface, Shirou saw a truth that she had hid even from herself, that deep down, the innocent girl named Arturia was still there. Shirou could only see her for this, not the mask she wore of a machine king. This initially led to friction between them as Shirou did not want to see her fight and she wanted only to fight and win the Holy Grail. Eventually they would compromise to both fight and protect one another.
As time passed Saber’s actions became less and less pragmatic with each day, and more concerned simply with protecting this boy. Much of their time was spent not fighting enemies, but waiting around for info on their enemies at Shirou’s home, which gave them a lot of time to bond as people. With each day Saber became more and more nervous around Shirou, who was nervous around Saber from day one, seeing what he believed to be them most beautiful person he had ever met. Eventually Saber ran out of Magical Energy, and due to a faulty contract, could not replenish from Shirou, leading them to be forced to engage in sexual intercourse to resupply her and to recreate the contract so the path between them was no longer obstructed. While they were able to defeat one of their strongest enemies in the battle that followed immediately, their interactions had become much more awkward the next day, with Saber now being unable to suppress her emotions as she could before, with her heart racing every time she saw him. She also had caught a glimpse of his past in a dream, as he had hers. She confronted him about his distortion, believing he needed the Holy Grail as much as she did to save him from the fire that killed his family.
As Shirou saw more of Saber’s past, he found her life to be too unfair and wished to do something about it, noticing that she had smiled in a way she never smiled in life while she was living with Shirou. Eventually he learned of her wish on the Holy Grail and was infuriated because he knew it would mean her elimination. He was determined to free her of this distortion. He made her go on a date with him to try to get her to enjoy her time with him to convince her. She did enjoy her time with him, and at many points seemed happier than she had ever been in her life, but once Shirou tried to convince her to stay this way, she put the mask over her emotions and lied to herself and him that the only thing that mattered was her duty as a king. Only this time, that lie actually hurt, not because she wanted to be with him, but because she knew he wanted to be with her and that by denying it, she wasn’t just making herself unhappy, she was also doing so to him, so each denial of her feelings broke her heart as she saw his face in reaction.
Eventually they would be confronted by Gilgamesh: King of Heroes, whom stayed from the fourth Grail War. Both Saber and Shirou were defeated by him, but Shirou stood up, even with a half sliced body and told Saber how much he loved her, leaving her amazed that someone could see so much value in her who never saw value in herself other than as a king. When it seemed that Shirou would be killed, a familiar sheath formed in his hand that protected him from Gilgamesh’s attack. After Gilgamesh retreated, Saber was overwhelmed with happiness, her sheath had been inside Shirou’s body and even though she could not save anyone else, she had saved him. That night, Shirou continued to try to convince her to return to being Arturia, and she continued to refuse, her face coming closer to crying every time she did so. She did give in to her feelings that night however and choose to make love to him, but under the excuse that she needed more Magical Energy, planning to “return to her regular self” after, but found herself unable to, so she let herself sleep the rest of the night away with him like this before trying going back to her professional self.
When she woke up the next morning, she couldn’t find him, and the only thing she could think about was him, even going so far as to try to predict his future with the stars, something she had never tried for anyone, and then she realized the huge change in her thinking from when she only cared about obtaining the Holy Grail. In the middle of a conversation with Rin Tohsaka, she senses that Shirou is in danger at the church and runs to his rescue. When she gets there she sees Shirou trapped in his own personal hell, a room full of victims of the event he survived and has shaped him for his life. Kirei Kotomine offers the Holy Grail so he can change that event, and he, with tears in his eyes, refuses, believing, from his attempts to convince Saber, that one must accept the past as unchangeable and make change happen in the present and future. Saber is moved by this choice, unable to comprehend how he could refuse it, and then Kotomine tells her to kill Shirou in exchange for the Grail. She goes to him and raises her sword, but ultimately she was unable to bring it down. For the first time, someone who was a source of happiness for her, was more important than her ideals and her kingdom, and she could not bring herself to sacrifice that one person for it the way she did to so many others. This inability to make this decision makes her realize she isn’t King Arthur anymore, and that she stopped being that person when she let go of the sword, meaning there was no mistake, she fulfilled her duties as the king until the end and she should be proud of them. Having come to terms with her kingship, and letting go of the wish she had to redo it, she chooses to fulfill her role as his sword and shield, a role she choose willingly.
It is then revealed to both of them that the Holy Grail is actually corrupt, and this is why Kiritsugu ordered her to destroy it. Shirou and Saber both resolved to destroy it, realizing that if they don’t, it would have been the end of the world. They did so with the mindset that Saber will disappear in this battle. They approached their final opponents, Gilgamesh and Kotomine. Shirou faced Kotomine and Saber faced Gilgamesh. To the end Saber refused Gilgamesh’s advances and when he tried to insult her for being destroyed by her own country, she simply told him it was better than destroying her own country. Prior to the final battle, Shirou gave Saber back her sheath, which she used to defeat Gilgamesh. It isn’t known how, but when the Holy Grail was destroyed, Shirou found a way to do so that wouldn’t expend the last of Saber’s Magical Energy. With the restored path between them Shirou was able to supply her, but his circuits were so weak that he needed help from Illyasviel and Rin Tohsaka while he trained his circuits to become more adept at supplying magical energy. Within a few years he should be able to maintain her on his own with an occasional dalliance if he trains his circuits enough. On the night the Grail was destroyed, Saber finally admitted her feelings to Shirou and accepted herself as Arturia. She is satisfied with her efforts as the king and accepts that her end will not change. Until that day comes, she continues to stand by the side of her former Master turned lover, having claimed the peace she never could before and finally smiling for herself as well as those around her.