Race: Slime ➔ Demon Slime ➔ Ultimate Slime Affiliation/Status: Leader of the Jura Tempest Federation / One of the Octagram Disaster Rank: Special S Class (Catastrophe) Titles: Chancellor of the Monster Federation, Newbie, Chaos Creator Raphael (Lord of Wisdom) ➔ Ciel (Manas): Rimuru's partner who handles thought acceleration and analytical appraisal. Later develops a "will." Beelzebuth (Lord of Gluttony) ➔ Azathoth (God of Void): The ability to prey upon, absorb, and convert anything into his own power.

Noir (Primordial Black) / Diablo. Rimuru's subordinate. A Demon Lord with absolute loyalty. Azazel (Lord of Temptation): Authority to completely dominate opponents through mental control, thought manipulation, and hallucinations. Azathoth (God of Void): An Ultimate Skill bestowed by Rimuru. It warps the laws of the world.

Race: Demon ➔ Demon Lord Affiliation: Jura Tempest Federation / Black Numbers Status: Direct subordinate of Diablo, bodyguard to Masayuki Title: Mad Demon Lineage: Black Lineage (Diablo's lineage) Generation: Modern Breed (A relatively young demon born a few hundred years ago) Unique Skill 'The Decreaser': A combat-specialized ability that attenuates or nullifies an opponent's defense and resistance, making it easier for his attacks to land. Indomitable Spirit: His core as a spiritual lifeform is incredibly sturdy, possessing miraculous toughness that allows for immediate regeneration even after taking hits from superior foes.

An "Otherworlder" who came to the different world from Japan. Appearance: A beautiful boy with blond hair and blue eyes (transformed upon crossing over). Personality: An extreme coward and an ordinary pacifist. Unique Skill 'Chosen One': Constant Luck: Every action leads to a convenient result (a miracle). Absolute Misunderstanding: Just by standing silent in fear, those around him favorably misinterpret him as a "hero of deep insight." Absolute Charisma: Enemies lose their will to fight, and allies break their limits to grow stronger. Automatic Evasion: Enemy attacks all miss due to accidental happenings. Ultimate Skill 'Rudra (Lord of Heroes)': As the story progresses, this evolves into a terrifying ability to summon and manifest past heroes or "strong individuals he once had a connection with" from the Soul Corridor to fight.