True to his title of 'Avatar of Greed', Mammon is naturally greedy and always seeking out opportunities to profit without putting much work.

Although he's the second eldest, he acts immaturely when he doesn't get his way and is the biggest troublemaker of the brothers. 

He's egotistic and prideful, though it seems that it is only a façade to cover up his soft nature. 

There are moments where his true personality comes out — such as when he enjoys the Human Realm’s snow with you.