How do I upgrade my Heroes?
The effects and stats of your Heroes can be improved by using Coins of War and Wisdom earned via Island Quests. Click on the hero icon in the right menu, then click on "Help this hero to reach the next level", then click on "Use coins".
Spending coins will increase their overall experience toward a level. Once you reach a new level, the abilities of your Hero will improve, up to a maximum of level 20.