Who is Momus?

Actually, ‘Momus’ was a Greek god.  So it’s a he, not a what.

According to the very short entry at Wikipedia:Momus or Momos (μῶμος) was in Greek mythology the god of satire, mockery, censure, writers, poets; a spirit of evil-spirited blame and unfair criticism. His name is related to μομφή, meaning ‘blame’ or ‘censure’. He is depicted in classical art as lifting a mask from his face.”

So there you have it, Momus.