Born the daughter of Uther Pendragon, Altria Pendragon, originally King Arthur, was concealed during childhood due to her gender being deemed unfit for kingship. Raised by Sir Ector under the name Artorius alongside his son Kay, she trained as a knight. At fifteen, she fulfilled the prophecy of Britain's rightful ruler by drawing the sword Caliburn from a stone. This act halted her aging, transforming her into a symbol dedicated solely to her kingdom's welfare. Her reign united Britain against invaders like the Saxons and established Camelot with the Knights of the Round Table. Internal strife, including Lancelot's betrayal and Mordred's rebellion, culminated in her mortal wounding at Camlann. Dying, she entrusted Bedivere with Excalibur's scabbard, Avalon, harboring regrets over her kingship. Summoned as a Saber-class Servant in multiple Holy Grail Wars, Altria served Kiritsugu Emiya during the Fourth War (*Fate/Zero*), clashing with his ruthless tactics. Her wish for the Grail was to undo Britain's destruction by selecting a different ruler. In the Fifth War (*Fate/stay night*), her path diverged: The "Fate" route saw her bond with Shirou Emiya, reject her wish upon discovering the Grail's corruption, destroy it, and return to her era. During "Unlimited Blade Works," Caster enslaved her before her contract transferred to Rin Tohsaka. In "Heaven's Feel," the Grail's mud corrupted her into Saber Alter—a darker, colder version serving Sakura Matou. As Saber Alter, she retained strategic brilliance but embraced tyranny, rejected her past ideals, and favored junk food over refined cuisine. In the parody spin-off *Fate/Grand Carnival*, Altria appears as "Mysterious Cat X" in comedic segments where Chaldea's Servants address perceived deployment inequalities. This lighthearted role contrasts her usual solemnity, aligning with the event's absurd tone. Altria is central to the "Saberface" phenomenon, where characters resemble her due to shared designs. This includes her alternate selves (Saber Alter, Saber Lily) and unrelated figures like Jeanne d'Arc, representing different individuals or aspects across media. Her combat abilities center on wielding Excalibur for massive energy attacks, augmented by skills like *Charisma* (boosting allies' attack) and *Mana Burst* (enhancing Buster-type attacks). Post-upgrade, she gained *Dragon Reactor Core*, temporarily converting all card types to Buster and amplifying her Noble Phantasm damage. As Saber Alter, she wields the corrupted Excalibur Morgan.