Gold is a renewable resource required to develop your Town.
 
You can earn it in multiple ways:

• Automatically in the Mine (the higher the level of the building, the faster it mines at the more gold it can store before collecting)
• Trading items with your Town’s MastersSelling items in the inventory
• Completing Campaign and Tower of Trials missions
• Defeating other players in Arena

Gold is required for:

• Completing and upgrading all buildings
• Researching technologies at the Lyceum
• Upgrading your Heroes in the Barracks