That Time I Got Reincarnated as a Slime (2018)

S2E24 Octagram

Rimuru confronts Clayman, pressing him for information about his mysterious benefactor. However, even when faced with defeat, Clayman refuses to divulge any secrets. With no options left, Rimuru eliminates him. Following Clayman's demise, Carrion and Frey declare their resignation from their roles as Demon Lords, reducing their ranks from ten to eight, including Rimuru. Guy insists that Rimuru devise a new name for their alliance, leading Rimuru to propose "Octagram," symbolizing the eight Demon Lords as eight-pointed stars. This marks a significant turning point, with a slime now among the Demon Lords, heralding a new era.