Jeanne d’Arc

Heroic savior of France in the middle ages, and tragic saint blindly venerated by Caster. Jeanne was a mere shepherdess, but she joined in on the Hundred Years War after receiving a revelation from God. It’s said that she helped free Orléans, which was surrounded by the English army, thereby contributing to France’s victory. However, in the midst of the war, she became caught up in strife between French factions vying for the throne, and during a battle near Compiegne, she was taken prisoner by the English army. After that she was found guilty for heresy and burned at the stake. Catholics believe that the flesh will eventually revive again, so burning at the stake is considered to be one of the most severe punishments. Caster despairs Jeanne’s tragic end and despises God for not saving her from her horrible fate. This spurs Caster to commit atrocities as a means of blasphemy against God.

Fate/Zero Animation Guide I: Glossary of the holy grail war I

Jeanne is a Ruler-class Servant in Altera’s army.
She is world-renowned as the “Holy Maiden” and the savior of France in the Hundred Years War. Although the end of her story was far too tragic and cruel, she does not curse her own fate, but accepts it as she fights on with a soul of steel.
Like Iskandar, she is a Top Servant.
She acts as a peacekeeper after being summoned by the Moon Cell.
However, after she fights Altera, she realizes that Altera’s true nature is not evil, but that she is full of uncertainty. Jeanne joins Altera’s side in order to develop a better understanding of her.
She is much closer to Altera than the other two knight-class Servants.
“The Ruler who was trusted to handle the situation is making waves once again…” the rumor mill might say. It would seem that Jeanne’s penchant for running off and stirring up trouble remains a hot topic even in the Servant world. “…what a cruel twist of fate.”

Fate/EXTELLA material: Encyclopedia of Fate EXTELLA