Killing mobs specifically for wealth gain is called farming.
Gold has many uses:
- Purchasing goods and services from players
- Purchasing items from NPCs
- Paying for maintenance costs associated with buildings and vendors
- Upgrading vendors, guards, and buildings within a city
- Repairing damaged buildings
- Funding the use of a Siege Spire
There is a limit on the amount of gold the player or their buildings can hold at once, and gold may not be deleted.