Aldebaran

Aldebaran, or Al,an eccentric, helmet-wearing, one-armed knight summoned from Japan 18 years ago who initially serves as Priscilla Barielle's loyal vanguard but later emerges as a central antagonist After surviving a brutal decade as a sword slave on the Gladiator Island of Ginunihive, Al developed a hyper-pragmatic outlook and a localized, reality-bending temporal power called Matrix Redefinition, which allows him to loop time upon death within a specific domain to outmaneuver stronger foes. uncovering that his true name is Rigel Natsuki and that he is actually an artificial creation crafted 400 years ago by the Witch Echidna rather than Subaru's actual future child This deep connection to the ancient past fuels his drastic shift where he turns against the Emilia Camp with the ultimate, terrifying objective of completely erasing Natsuki Subaru from existence