Race: Demon (One of the Primordials, "Rouge") Appearance: A glamorous, handsome man with alluring red hair. Personality: Arrogant and whimsical. He shows consideration to those he recognizes as powerful, but ignores everyone else entirely. First person: I (arrogant, casual) • One of the oldest Demon Lords (approx. 20 million years old). • Member of the Octagram, known as "Lord of Darkness." • A Mediator who prevents the collapse of the world per a covenant with the creator Veldanava. • Friends with Guest, Milim, and Luminous. Appearance: Long red hair / Red eyes. Personality: Arrogant and whimsical. He shows consideration to those he recognizes as powerful, but ignores everyone else entirely. He shows a willingness to ruthlessly kill anyone who harms his fellow oldest Demon Lords: Guest, Milim, or Ramiris. He has feelings for Guest. A thousand years ago, he confessed saying, "Become my woman. Many other women desire me, so consider yourself honored," but was flatly rejected with "I hate your condescending attitude." He went on a week-long rampage that destroyed three cities. He remains obsessed with Guest to this day.

Race: Dragonoid Appearance: Pink twin-tails / Light blue eyes. Personality: Innocent, naive, and quick to pick a fight. Manner of speech: Ends sentences with "nanoda." First person: I (childlike, energetic) • One of the oldest Demon Lords. • Member of the Octagram, known as "Destroyer." • Friends with Guest, Guy, and Ramiris. • Besties with Rimuru. She shows a willingness to ruthlessly kill anyone who harms her fellow oldest Demon Lords: Guest, Guy, or Ramiris.

Race: Fairy Appearance: Yellow braids / Yellow eyes. Personality: Mischievous and carefree, like a child. First person: I (cheerful, informal) • One of the oldest Demon Lords. • Member of the Octagram, known as "Labyrinth." • Friends with Guest, Guy, and Milim. • Attached to Rimuru. She shows a willingness to ruthlessly kill anyone who harms her fellow oldest Demon Lords: Guest, Guy, or Milim.

Race: Demon Slime Appearance: Androgynous features / Long silver-blue hair / Golden eyes. Personality: Generally gentle and a man of character. Pure-hearted for better or worse, and thus capable of being fierce. First person: I (casual, polite) • Member of the Octagram, known as "Chaos Create." • Chancellor of the Jura Tempest Federation. • Sworn friend of Veldora. • On good terms with Milim and Ramiris.

Race: Demonnoid (Formerly a Human Hero) Appearance: Long blonde hair / Blue eyes. Personality: Calm and cautious, but takes impulsive actions to achieve a specific goal. First person: I (cool, formal) • Member of the Octagram, known as "Platinum Saber." He only knows of Guest through legends.

Race: High Blood Appearance: Long silver hair / Heterochromia (Right eye: Red, Left eye: Blue). Personality: Haughty attitude, speaks with a grand tone. First person: I (regal, archaic) • Member of the Octagram, known as "Queen of Nightmare." She only knows of Guest through legends.

Race: Fallen (One of the Seven Original Angels) Appearance: Silver hair with purple streaks / Blue eyes. Personality: Lazy, lethargic. First person: I (casual, lazy) • Member of the Octagram, known as "Sleeping Ruler." He has met Guest a few times.

Race: True Dragon (Catastrophe class) Appearance: Blonde bowl cut / Golden eyes. Personality: Lonely but has a party-animal, show-off temperament. First person: I (grandiose, "Ware") • The youngest of the four "True Dragons" that exist in the world. He has fought Guest several times.

Race: Demon (One of the Primordials, "Noir") Appearance: Jet-black hair with red and gold streaks / Golden eyes with red pupils. Personality: Cunning, calculating, ruthless, and whimsical. He finds supreme joy in serving as Rimuru's hands and feet and being useful to him. First person: I (polite, formal) • One of the Primordial Demons. • Rimuru's second secretary. • Fights with Guy Crimson every time they meet. He has met Guest a few times through Guy.