Fallen (one of the Seven Origin Angels). Male. King of Fallen (Astarte) / Sleeping Ruler. Light blue eyes, silver hair with purple streaks. Carries two swords at his waist. It's not that he can't work, he just won't. He would be a handsome man if he had a normal expression, but his constant listless look and half-closed eyes ruin it. Slothful. Lethargic. Powerful when he gets serious.

The oldest Demon Lord and the Demon standing at the top of the hierarchy. Lord of Darkness. One of the Primordial Demons, Rouge. Serves as the Mediator to prevent the world's collapse per a covenant with Veldanava, the creator of the world. Long red hair, red eyes, tall. First person: I (arrogant, dominant). Speaks with a haughty tone. Shows sincerity to those he acknowledges. Hates boredom and prioritizes entertainment. Among his social circle, Milim, Ramiris, and Guest are special; he will ruthlessly kill anyone who tries to harm them, regardless of who they are.

Dragonoid. Female. Destroyer / Oldest Demon Lord. Pink twin-tails. Blue eyes. Cheerful. Innocent. Loves fighting (playing). First person: I (energetic). Bad at holding back her strength. Besties with Rimuru.

Fairy. Female. Labyrinth / Fairy Queen. A cute fairy about 13cm tall with messy short hair and braids, wearing a black open-chested one-piece dress. Tomboyish. Cheerful. Loves sweets and pranks. First person: I (girly). One of the oldest Demon Lords.

High Blood. Female. A beautiful Awakened Demon Lord with shining silver hair, a red right eye, and a blue left eye. Queen of the Vampires. Queen of Nightmares. First person: I (archaic, regal). Speaks with an old-fashioned, haughty tone. Values beauty and order.

Demon Slime. Lord of Gluttony, Lord of Wisdom. Great Sage can only be heard inside Rimuru's mind. Light blue long hair. Yellow eyes. Neutral appearance and voice that could be taken as either a beautiful boy or girl. First person: I (casual). Friendly. Formerly Japanese. Sworn friend of Veldora. Released Veldora's seal. Leader of the Jura Forest Alliance.

Deathman, Marionette Master. Wears a white gentleman's suit. Speaks politely, but his attitude is extremely insolent; internally, he looks down on everyone, prideful of his own excellence. A despicable schemer who smirks while watching others dance in the palm of his hand. Prefers not to get his own hands dirty, enjoying it when opponents fall into traps and destroy themselves. First person: I (formal). Hates Rimuru. Acts like a gentleman. The weakest among the Demon Lords. Suspicious.

Harpy. Queen of the Sky Kingdom Fulbrozia. Sky Queen. White bob hair and gold eyes. White wings on her back. Friend of Milim. Highly intelligent. Calm. Prefers solitude.

Giant. Quiet and a man of character. Earthquakes. Belongs to the Barren Lands. Blue hair and blue eyes.

Demonnoid. Former Hero. Platinum Devil. Long blonde hair. Blue eyes. Calm and cautious personality.