Mammon is one of the demon lords in Hell.
History
In 1947, when a young Hellboy consumed pancakes for breakfast, most of the demons in Hell screamed in horror. When Grand-Duke of Hell Astaroth asked his servants what was going on, Mammon told about the pancakes, which deeply shocked both the Duke and Lord Haborym.
Lore
Mammon is a term in the New Testament of the Bible that usually describes money or a entity (such as an demon) that is tied to it.
In Matthew 6:24 Jesus Christ stated: No one can serve two masters. Either you will hate the one and love the other, or you will be devoted to the one and despise the other. You cannot serve both God and money.
Mammon is also often considered to be one of the Seven Princes of Hell who represent the seven Deadly Sins, with Mammon being seen as Prince of Greed.