Artoria Pendragon, better known as Arthur Pendragon and King Arthur, is regarded as a male in history but is actually female. She is the "Once and Future King" and a legendary hero of Britain known as the King of Knights. She used to wield the sword from the stone, Caliburn, but it was eventually destroyed and the Lady of the Lake gifted her with Excalibur and Avalon.
In Fate/Prototype: He is presented as male instead, conserving his original name of Arthur Pendragon. Also called Prototype Saber, he is the Saber-class Servant under the control of Ayaka Sajyou.
In Fate/stay night: Saber is summoned in the Fifth Holy Grail War as the Servant of Shirou Emiya. Shirou had been having dreams of Excalibur in the days leading up to the start of the Holy Grail War after receiving his Command Spells and, while stumbling in his shed during his escape from Lancer, Avalon, hidden inside him, reacts to the traces of a magic circle and summons Artoria as his Servant.
In Fate/stay night: Heaven's Feel: Corrupted by Angra Mainyu, Artoria is vastly different from her normal self. She is also called Saber Alter/Black Saber. The results of her alteration is not only within Artoria's interior but also extends to her outward appearance. The color of her skin becomes pale, and the pupil of her eyes that were at first concealed behind a black visor during the moment of her summoning becomes golden from her original green eye color as well. Because the armor she wears was dyed jet black and grew in weight due to changing into a heavier armor, its power has increased more than normal.
In Fate/Zero: Saber is summoned by Kiritsugu Emiya to participate in the Fourth Holy Grail War on behalf of Jubstacheit von Einzbern and the Einzbern family. Kiritsugu partners Saber with Irisviel von Einzbern, to act as Saber's Master in the open while he acts from behind to win with his own methods.
In Fate/Grand Order - First Order: She remains the corrupted version, known as Saber Alter.
In Fate/Grand Order Camelot: The being called Goddess Rhongomyniad came into existence in the world that Bedivere, due to the wish of wanting his King to not perish after the battle of Camlainn, refused to throw Excalibur back into the Lake even after the third time.
