A slime standing 160cm tall. Genderless, soft-hearted, and deeply protective of his companions.

The Labyrinth Fairy who created the dungeon in Tempest. She conducts various research projects inside the dungeon.

The final boss of the 100th floor of the dungeon. He also assists Ramiris with her research.

Noir, the Primordial Black. An eccentric individual who deifies Rimuru. He currently serves as Rimuru's second secretary.

A companion brought by Diablo, formerly Blanc, the Primordial White. Appointed as Tempest's diplomatic attaché, she attends Council meetings. She has a calm but cold personality and was responsible for the Lake Shore Incident in the Eastern Empire.

A companion brought by Diablo, formerly Jaune, the Primordial Yellow. She is the Chief Justice of Tempest's Supreme Court. She frequently bickers with Ultima, requiring Diablo's mediation. While they don't seem to hate each other, they are highly competitive. Arrogant and mischievous, she used to drop nuclear magic on Leon's territory whenever she was bored.

A companion brought by Diablo, formerly Violet, the Primordial Violet. Appointed as the Chief Prosecutor of Tempest. She often fights with Carrera, with Diablo acting as the mediator. She is very fond of Rigurd, calling him 'Uncle', while Rigurd dotes on her like a daughter, calling her 'Young Lady'.

Originally a high-ranking spirit under Leon Cromwell, given to Shizue, then absorbed by Rimuru. He was manifested at Veldora's request and named Charybdis by him. Originally a high-ranking fire spirit, he evolved into a Flame Lord upon receiving his name. Having spent a long time inside Veldora and Rimuru's stomach, he can now use wind magic as well. He serves as Veldora's assistant.

One of the Octagram Demon Lords. Originally living in Dagruel's territory, he was kicked out and came to Tempest. Rimuru initially tried to refuse, but accepted him due to Guy's request and Ramiris's lack of staff. He now works as Ramiris's assistant.