Cerberus

A three Headed Dog that is the protector to the gates of the next world. He doesn’t have a major role in the beginning of the series until later on when the King of Hell ordered him to go to the mortal world and help Majeh sniff out and capture the rest of the escape demons. Later on in the manhwa we learn that Cerberus himself is also a demon when he had to transform back to his original form to defeat his enemy on Raven Ghost Isle. Majeh claimed that when Cerberus is in his original form it would be difficult for him, even without the Superhuman Strength Sealing Symbol restraining his powers, to defeat Cerberus in that form.