Zeldris, the Demon King's younger son and Meliodas's brother, initially led the Ten Commandments as the holder of the Commandment of Piety. Serving as his father's representative and executioner, he ruthlessly enforced demonic law, earning the epithet "the executioner." Three millennia before the main events, he idolized Meliodas during their shared tenure in the Commandments. His personality fractured after two traumas: Meliodas’s betrayal of the clan for the goddess Elizabeth, and the Demon King’s order to execute the rebellious Vampire Clan—which included Zeldris’s lover, Gelda. Defying his father, Zeldris secretly sealed the entire Vampire Clan to spare Gelda, an act fueled by love. This choice and Meliodas’s abandonment bred deep resentment toward his brother and Elizabeth, whom he blamed for Meliodas’s actions.

Outwardly calm, collected, and commanding, Zeldris displays strong leadership and combat confidence bordering on arrogance against weaker foes. Beneath this façade simmers explosive rage when facing betrayal or past trauma, fueling open hostility toward Meliodas and Elizabeth. Yet fragments of his former sincerity endure—loyalty to his mentor Cusack and reluctance to harm women unnecessarily. His core motivation was attaining the Demon King’s throne to revive Gelda, whom he believed dead. This ambition clashed directly with Meliodas’s quest to break his and Elizabeth’s curses, culminating in a brutal Camelot duel where Zeldris unleashed his signature "Ominous Nebula," a dark vortex powered by the Demon King.

A turning point came when Meliodas revealed Gelda lived, merely resealed, and offered her freedom for Zeldris’s aid. Instantly abandoning his throne quest, Zeldris relinquished his Commandment and allied with Meliodas to gather the remaining Commandments and shield him during their absorption. This alliance shattered when the Demon King possessed Zeldris after Meliodas rejected the full power. Manipulated by his father’s illusion of Gelda falsely accusing Meliodas of deceit, Zeldris realized the Demon King would never permit their reunion. He consciously rebelled, resisting possession internally. Combined with attacks from Meliodas, Ban, and Ludociel, this forced the Demon King from his body.

After the Demon King’s defeat and Meliodas’s sacrifice of his demonic powers, Zeldris assumed rulership of the Demon Realm. Sixteen years later, during *Four Knights of the Apocalypse*, he governs with demonic power visibly covering much of his body. His underlying drive for underworld peace and harmony, once noted by his father, hints at a potential return to his pre-tragedy sincerity.