The Castle Throne is where you can use gold or crystals to purchase new Heroes to lead your army.
Upgrading the Castle Throne to higher levels opens up new heroes to buy. Heroes available in the next level of upgrade are shown darkened, and cannot be purchased until the building is upgraded.
Upgrade Levels
Level 1
Cost: Free. (It starts at level 1)
Heroes: Grullborg Grimtooth, Steel Armoured Popo
Level 2
Cost: 1,500 gold.
Heroes: Oni the Brute
Level 3
Cost: 6,000 gold.
Heroes: Robo Jack Mk. II, Joey the Skull-Splitter
Level 4
Cost: 15,000 gold.
Heroes: Rhino the Executor
Level 5
Cost: 28,500 gold.
Heroes: Lutea the Summoner, Dragonzord
Level 6
Cost: 62,000 gold.
Heroes: Khobbit the Spartan, Jasmine Timberlake
Level 7
Cost: 92,000 gold.
Heroes: Omni Knight, Frei The Sky Princess
Level 8
Cost: 128,000 gold.
Heroes: Sir George Lancelot, The Mighty GhatotKacha
Level 9
Cost: 170,000 gold.
Heroes:Khronos, Sir Kholai, Lilith The Succubus Queen
Level 10
Cost: 218,000 gold.
Heroes: The Great Sun WuKong, Holy Angel Seraphiel, Power Go Goblins