Ouken, a prince of the Underworld royal family, rose to prominence as Commander of the Underworld Order, renowned as the "Sword King of the Underworld" for his unmatched martial skill. He began as a compassionate visionary, striving to forge a knightly order to oppose his brothers’ tyrannical armies. This idealism shattered at age 25 when he inherited true immortality from his divine father, Satun. The curse corroded his humanity, warping him into a merciless, pleasure-driven predator who savored orchestrating others’ torment. As an immortal, his form mutated into a silhouette of liquid shadow encased in silver armor, its horned helm twisted into a demonic visage. The metal fused with his regenerative body, healing seamlessly from damage. Upon regaining mortality, he reverted to a human physique—tall, black-haired, mustached—though his combat instincts remained. Immortality rendered Ouken a near-unstoppable force. He wielded swords with surgical precision, targeting limbs and tendons to prolong victims’ pain. His signature "shirasampe" technique launched debris at blinding speeds to disorient foes, countered only by Bojji’s reflexes. Superhuman strength let him pulverize fortifications and battle entire armies single-handedly. Yet his fractured psyche made him a pawn for manipulators like Miranjo, who unleashed him to siege Bosse Kingdom. Notable clashes pitted him against Queen Hiling’s guardian Anne, his former Underworld knights, and Bojji, whose speed initially outmatched him. Ouken’s regeneration and relentless brutality tipped scales until King Bosse crushed his form into a metal orb, entombed in stone. Later freed by Kingbo, his severed head lay inert until retrieved from a cavernous catfish. Redemption arrived when his eldest brother Desha traded his memories to the Divine Treasure Vault, stripping Ouken’s immortality and restoring his mind. Freed from the curse, Ouken reclaimed his noble spirit and strategic genius, later slaying a deity in solo combat. His arc hinged on fraternal bonds: Desha’s unwavering loyalty led him to prioritize Ouken’s salvation over his throne, while mentor-brother Despa championed Ouken’s right to rule, cementing their fractured yet enduring kinship.