Alastor is the infamous entity known as "The Radio Demon", one of the many powerful Overlords of Hell. He is a major character in Hazbin Hotel and offered to assist Charlie in her endeavors, albeit, for his own amusement. 

Alastor's behavior, mannerisms, and even his voice are similar to an old-fashioned radio announcer, for instance when he refers to modern television as a "picture show". Alastor deviates from the crass nature prominent in Hell in favor of an amiable persona. As a result, he is always smiling and acts polite. He never stops smiling because he believes it shows power and dominance. If a rival were to frown, he would see them as weak.[2]

He is narcissistic, not seeing many people quite up to his level. However, that does not make him reckless. Despite being extremely powerful, Alastor is fully aware that there are other demons and entities that rival him in terms of power, such as the Overlords. For this reason, he is wary around such demons, as they could potentially harm him if he is not careful.

Alastor also seems to have a moral compass, which is actually "not normal".

He has been noted to be quite sadistic and to have masochistic tendencies. Despite this, he genuinely wants to help Charlie run the Happy Hotel, albeit for his own amusement rather than idealism. Alastor even dismisses the idea that redemption is possible.

Once again, no changes from the show.