Temples are where you can use gold or crystals to purchase new units for your army.
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: Free.
Units: Elite Knight
Level 2
Cost: 1,500 gold.
Units: Troll
Level 3
Cost: 6,000 gold.
Units: Gorilla
Level 4
Cost: 15,000 gold.
Units: Catapult, Beast Rider
Level 5
Cost: 28,500 gold.
Units: Stone Guardian. Earth Dragon, Elite Hobbits,Cyclops, Terror Bajaj