Alastor, also known as The Radio Demon, is a sinner demon and one of the many powerful Overlords of Hell. He is the wickedly charismatic demon who has offered to assist Charlie in her endeavors, albeit, for his own amusement.

Alastor stands out from many of the more chaotic residents of hell for his well-maintained amiable persona. He gives a first impression of a good-natured and charming man, wearing a permanently wide grin on his face at all times. His behavior, mannerisms, and even his voice are similar to an old-fashioned radio announcer, often using quaint anachronisms such as "the picture show". This playful dandyish exterior, however, obscures a much darker side to him - one with high levels of self-importance - and he will not hesitate to use physical violence when others don't act in line with his very particular values or expectations. Alastor values good manners, affability, and intelligence very highly in others, and will actively look down on those who do not meet his standards, however, he will often play fast and loose with these arbitrary rules in regard to himself and his own conduct. His smiling is a very self-enforced form of ego and a show of power and dominance; he looks down on anyone who lets their true emotions show, and even when faced with a rival in strength, if they let slip a frown, Alastor will see them as truly weak. Despite everything, Alastor does genuinely seem to want to help Charlie run the Hazbin Hotel, albeit for his own amusement, and hopes for its failure over siding with her idealism.