ゼギオン, 幽幻王 (Yuugen Ou), Mist Lord
One of the ninth group of subordinates to be named by Rimuru Tempest. He was originally an injured monster that looked like a Japanese rhinoceros beetle which he thought was cool so he took him in and sheltered him inside the Labyrinth. Source: The Time I Got Reincarnated as a Slime wiki