Caster-class variant of Artoria Pendragon, introduced during the Fate/Grand Order 5th Anniversary event. First debuted in the second opening of Cosmos in the Lostbelt and is a major character in Lostbelt no. 6: Avalon le Fae.
She is an alternate version of Artoria who was chosen by the Staff of Selection instead of the Sword of Selection, leading her to study magic instead of becoming a knight. Notably, she does not bear the Pendragon name, unlike her selves from Proper Human History. This is because Artoria Caster is completely unrelated to the Artoria from Proper Human History; she was created explicitly to fulfill the prophecy of Faerie Britain and destroy the Lostbelt, a mission originally assigned to Lostbelt Morgan that she abandoned.
Her outfit changes based on her Ascension level: