Pluto is bonded to hellhound Cerberus.
Pluto manifests in a fairly standard configuration for a demon. His body is regal, refined and wise in aspect: unostentatious but very well-designed. He wears his age well, but it is apparent that he is not a young demon. As with most traditional demons, he shows no obvious primary or secondary sexual characteristics, but takes the male pronoun as a courtesy to visitors who insist on labelling him one way or the other.
Cerberus is a relatively large, relatively lean and strong, short-haired hellhound with an obvious mutation: three heads. All three have working muscles, eyes, ears and the rest. However, Cerberus has only one mind.
Pluto and Cerberus have shown remarkable stability in surviving this long. (Time is a tricky area in hell, and for demons who spend most of their time at home, there is no way to translate hell's time to a useful Earth-year equivalent.)
Pluto is invariably calm and quiet. He receives visitors graciously, and always seems pleased to talk.