Gear
Your heroes can equip one weapon and piece of armor. However after being equipped, that equipment cannot be removed without spending premium currency. You can replace existing gear, however the older gear will be destroyed after removal. Instead of doing this, consider upgrading your gear instead by sacrificing unwanted items.
Team
Each hero has a type (offensive, defensive, support, etc.). Create a balanced team with heroes from each type. Use offensive types to do damage, defensive types to take incoming damage, and support types to heal. Your team's formation determins how your heroes will attack. The default formation consists of two slots in front, and three in back. Heroes that are in front will usually be attacked by enemies more often. Try to place your heroes in a way that is in your favor. Set defensive heroes in front to lessen the chance of weaker heroes in the back from being attacked. There are three other formations that you can set. Each formation conveys a passive stat boost to different spots. For example, the default basic formation allows 1% more defense to everyone in front.
Upgrades
Level your heroes by sacrificing unwanted heroes. After completing a level, you may recruit monsters or other heroes. If their stats are not great and do not seem useful, sacrifice them to improve your favority heroes.
