Mammon's greed overwhelms everything else. He deals with mortals who desire material wealth and provides them with the ability to spread that greed like an infection.
The greedy duergar and even some dragons are prone to falling prey to Mammon's temptations, and merchants and trade guilds are vulnerable to his bargains.
Mammon's cultists can gain the Grasping Hands trait. Cult leaders can also gain the Promise of Wealth trait.
Grasping Hands (Recharges after a Short or Long Rest)
As a bonus action, this creature makes a Dexterity (Sleight of Hand) check contested by the Wisdom (Insight) check of a creature it can see within 15 feet of it. If this creature succeeds, one hand-held item of its choice that it can see on the target magically teleports to its open hand. The item can't be one that the target is holding, and it must weigh no more than 10 pounds.
Promise of Wealth (Recharges after a Short or Long Rest)
As a bonus action, this creature chooses one creature it can see. Up to five allies of its choice become convinced that the target carries great wealth. Until the end of this creature's next turn, those allies gain advantage on all attack rolls against the target.