Zeldris, younger brother of Meliodas and son of the Demon King, commanded the Ten Commandments as his father’s enforcer during the Holy War 3,000 years ago. Bearing the title "Piety," he acted as the Demon King’s executioner and representative, his spiky black hair and shifting demon mark over his left eye mirroring Meliodas’s features. His crimson-clad form, armored with silver gauntlets, later transforms into demonic battle-plate with an exposed chest upon ascending as the Demon Realm’s ruler.

Outwardly composed yet ruthless, Zeldris harbors bitterness from Meliodas’s abandonment of their clan for Elizabeth of the Goddess Clan. This resentment fused with silent grief after he defied his father to spare Gelda, leader of the rebellious Vampire Clan, whom he secretly loved. Forced to seal her clan instead of executing them, his defiance sowed lasting internal strife, eroding his loyalty to the Demon King once he realized their reunion would be forbidden.

In battle, Zeldris merges innate demonic power with devastating techniques: Ominous Nebula, a spiraling vortex that devours and redirects assaults, and Hellblaze, unquenchable flames that halt regeneration. Though temporarily empowered by the Demon King’s borrowed might—a force dwarfed by his father’s true strength—he relies equally on strategic cunning, manipulating allies like the memory-altered Estarossa to maintain control over the Commandments.

Post-war, Zeldris assumes rulership of the Demon Realm, prioritizing stability over conquest. His alliance with Meliodas shifts from hostility to pragmatic cooperation, fueled by the latter’s vow to free Gelda and the revelation of her survival. This uneasy truce underscores his enduring capacity for loyalty and a veiled yearning for peace, balancing cold pragmatism with unresolved ties to his past—a ruler driven by duty, vengeance, and the fragile hope of reconciling love with legacy.