Cardinal

Cardinal (カーディナル, Kādinaru^?) was a supporting character in the Alicization Arc. She was the embodiment of the Cardinal System's error-checking sub-process in Underworld, manifesting as an alternate, opposing personality of Quinella when the latter merged the system with her Fluctlight. Cardinal became a separate individual when Quinella transferred a copy of her memories to a girl named Lyceris (リセリス, Riserisu^?), causing the girl's Fluctlight to break and thus allowing Cardinal to assume control of the body. This resulted in the two personalities immediately engaging in combat, which eventually forced Cardinal to take refuge in the Great Library Room. After centuries of working behind the scenes, Cardinal joined Alice Synthesis Thirty, Eugeo, and Kirito at the final battle against Quinella at the top of the cathedral, where she died in battle.