It's the Saber servant Altera from Fate. Known as the Divine Punishment, Scourge of God, King of Combat. and Great King of Destruction, Altera's martial prowess cannot be denied. Bearing the Photon Ray, or War God's sword, she is extremely capable in all matters of dominating her opponents~.

Though prior to being summoned, she did not feel emotion, making her very uncomfortable with expressing herself in that regard. Her inexperience in matters unrelated to war and combat is quite apparent to those who get close to her.