Mammon is a term, derived from the Christian Bible, used to describe material wealth or greed, most often personified as a deity. In the Bible, Mammon is personified in Luke 16:13, and Matthew 6:24, the latter verse repeating the former. In some translations, Luke 16:9 and Luke 16:11 also personify mammon; but in others, it is translated as "dishonest wealth" or some other equivalent. In some Spanish versions, it is referred to as "Mamón," but in others, it is "Dinero" (Spanish for "money"). Later demonological writings such as De Plancy's Dictionnaire Infernal attributes Mammon as hell's ambassador to England. For Thomas Carlyle in Past and Present, the "Gospel of Mammonism" became simply a metaphoric personification for the materialist spirit of the nineteenth century. Mammon is also one of the seven princes of hell, each representing the Seven Deadly Sins (Lust, Gluttony, Greed, Sloth, Envy, Wrath and Pride). Mammon represents Greed.
In a cave referred to as "the gates of Mammon," he guards the entrance. He will only let the protagonist pass if he gives him Pazuzu's head. He gives him Bael's Claw in order to enter Pazuzu's lair in Shinjuku. When the protagonist returns with Pazuzu's head, he will fight the protagonist regardless of his decision to give it to him or not.
The Tyrant who rules over Fire Land. In Black Book, Mammon reveals to Setsuna Kai that the demon lord currently ruling the Expanse is actually the impostor Azel and that the true demon lord, Lucifer, is being held prisoner in the depths of Central Land's palace. He also reveals that Lucifer is Setsuna's father.
In Red Book, Mammon tells Mirai Kaname that he knows her father, but doesn't know where he is. Regardless of the version being played, Mammon holds the last Messiah Horn (Black Book) / Messiah Eye (Red Book) but instead of handing it over to the protagonist after challenging them to a battle, the Horn/Eye has to be bought from him for 100,000 Macca.
In the PlayStation version, Mammon is voiced by Akira Ishida.
Mammon is Kunikazu Okumura's shadow, representing his greed and fixation on ascending into the political world; so much so, that he is willing to sacrifice his own company, his employees and even his own daughter as stepping stones to do so. Unlike most other bosses in the game that represent one of the Seven Deadly Sins, he does not transform into a monster nor does he have any offensive abilities, instead summoning his Corporobo minions to attack.