Temples are areas where you can use gold or crystals to purchase new units for battle.
Upgrading a Temple to higher levels opens up new units to buy. Units available in the next level of upgrade are shown darkened, and cannot be purchased until the Temple is upgraded.
Upgrade Levels
Level 1
Cost: 500
Units: Puppy Dragon
Level 2
Cost: 1,500 gold.
Units: Skeleton Archer, Mad Bull, Anu-Ki Warrior
Level 3
Cost: 6,000 gold.
Units: Fire Succubi
Level 4
Cost: 15,000 gold.
Units: Dragon Rider
Level 5
Cost: 28,500 gold.