Gold

Gold is the only paid feature in this game and it is not mandatory to obtain. Gold can speed up the construction of buildings, can speed up the training of troops, and can be used to bet on auctioned troops. The developers are always adding ways to spend gold. Recently they added the option to build a Mark Tower.

There are far more uses of gold. There are ways to obtain gold for free such as auctioning your troops and allowing another player to buy them for gold.