Saber of Red

A “Red” Servant, but one that has actually gone over to the “Black” camp. In contrast to the way the “Red” camp was unified under Shirou Kotomine as the only Master, she alone formed a partnership with Shishigou Kairi as her Master, as done in a normal Holy Grail War.
Her true identity is Mordred, one of the Knights of the Round Table. She is the Knight of Rebellion who ended King Arthur's legend. And she was also born as an inhuman being like King Arthur. After all, her father is King Arthur, and her mother is the mortal enemy of King Arthur, the witch Morgan.
Mordred's true identity is that of an artificial life-form; in other words, a homunculus. Accordingly, her life-span was extremely short, and she was born expressly for the purpose of killing King Arthur.
Far from hating King Arthur, she came to feel only yearning and admiration for her father, but when she confessed to King Arthur that she was his legitimate child not knowing what else to do, the king declared that he wouldn't acknowledge her as the next king, and this caused her longing to change completely into hatred.
And then, as if guided by a blood-stained destiny, Mordred fought against King Arthur on the Hill of Camlann. Though she was defeated, she managed to deal a fatal wound, and thus brought an end to King Arthur's legend.
As a Servant, she is first-class. Though her overall specs are lower compared to her father Arthur, the King of Knights, she possesses power worthy of the Saber class. By combining her jet propulsion through “mana Burst” and her sword “Clarent: Radiant Sword of the King,” her attacks can cut down most Servants in a single slash. Also, the defensive strength of her armor is also considerable aside from its abilities, so she was able to avoid a fatal blow despite being hit by a fully-powered attack from Berserker of “Black” that was strengthened by a Command Spell.
Her position in the story, rather than her actual character, is like that of Bonnie and Clyde, who lived by the motto “We have no tomorrow.” In the initial plot, it was decided that she would merely “rampage around and then exit the stage.”
Mordred's story also progressed in the background of the main story. She thought over her past in the form of a dream, and the meetings she then had with various Servants—particularly the conversation she had with the homunculus like her and his Servant—served as a turning point for her.
As a result, Mordred finally understood what her father sought when he pulled the sword from the stone. In the end, it was because she didn't understand that that Mordred continued to live in anguish. She did not feel fear towards the king like the other knights. After all, she herself was an inhuman being.
Even so, let's suppose that she might happen to encounter her father in a Holy Grail War somewhere. She would immediately fight and try to slash her father apart. Believing she has managed to understand her father and passionately wanting to surpass her father are separate matters for her.
She hates being treated as a woman, but also feels dissatisfied with being treated as a man, making a very complicated, or rather bothersome, Servant. She chose her clothes herself, so she does not seem to have a problem with her appearance being seen as feminine by others.
Also, she is being supplied with plenty of mana, but she is the type to proactively eat food in order to enjoy the present age without caring about the necessity. Her food preferences lean somewhat towards junk food, and she loves carbonated drinks.
Perhaps due to being summoned with a vague catalyst like a splinter of the Round Table, she has miraculously good compatibility with her Master Shishigou. Though it was not mentioned in the story, she liked Shishigou from the start based on his clothing due to her overflowing rebellious spirit.

Fate/Apocrypha material: Fate/Apocrypha Encylopedia