Zouken Matō, originally Zolgen Makiri, serves as a pivotal antagonist in the Holy Grail Wars. As the Matou family patriarch, he masquerades as the grandfather of Shinji and Sakura Matou, concealing a lineage stretching back five centuries. A co-creator of the Fuyuki Holy Grail War system with Justeaze Lizrich von Einzbern and Nagato Tohsaka, he devised the Command Seals and Master-Servant structure. Once motivated by reverence for Justeaze’s sacrifice as the Grail’s core, his prolonged lifespan corroded this idealism into a singular fixation on immortality. Centuries of decay forced him to sustain his crumbling body through Crest Worms—parasitic familiars that prolong his life and manipulate others. These worms were implanted into Sakura Matou after her adoption, a calculated move to revive the Matou lineage’s fading magical prowess. Her brutal indoctrination involved infestations conditioning her to host Angra Mainyu, the Grail’s corrupted essence. This fusion entwined her destiny with the Grail’s malignant energy, birthing the Shadow—a ravenous entity devouring Masters and Servants alike. In the Fourth Holy Grail War, Zouken exploited Kariya Matou, offering Sakura’s freedom in exchange for securing the Grail. Kariya’s demise cemented Zouken’s nihilistic convictions. By the Fifth War, he pivoted to leveraging Sakura as a pseudo-Grail vessel. When Shinji proved inept as a Master, Zouken summoned True Assassin, weaponizing the Shadow’s rampage to eliminate competitors. Sakura’s unraveling psyche and the Shadow’s independence eventually fractured his command. Kirei Kotomine’s exorcism annihilated Zouken’s corporeal form, yet vestiges of his consciousness lingered within worms embedded in Sakura. Confronted by Illyasviel von Einzbern—a homunculus mirroring Justeaze’s visage—he briefly reclaimed the memory of his ancient oath to honor her sacrifice. This ephemeral clarity allowed him to embrace dissolution, his final worm expiring as he faded into oblivion. Zouken’s methods epitomize merciless pragmatism, deploying psychological torment and Crest Worms—emblems of his parasitic magecraft—to dominate his kin. These creatures enabled both regeneration and subjugation, reflecting his fusion of sorcery and predation. Though once driven by altruistic aims, centuries of decay morphed him into an avatar of corruption, sacrificing all to perpetuate his hollow existence.