Greed begets greed, and by casting Avarice you will find that much of your enemy's coin becomes your own. Be wary, though; Avarice is costly to perform, and using it too often may result in a net loss of gold.
Avarice is one of the rituals within the Vein of Greed. In a new update, you are now able to not steal your enemies coins but you can now create your own by using your mana and transform them into Gold. Making the need to Mine Gold is rare to do.