Kingdom of darkness is the sixteenth and last stage. Its boss on the epic stage is The Dark Prince.
Unlike the other stages, every round has 4-5 minions and a boss.
The bosses are:
- Normal stage: Earthquake Serpent, Water Elemental, Nerezza the Assassin
- Mighty stage: Crimson Dragon, Mighty Mammoth Rider, Dorar the Fallen
- Valor stage: Waterio, Cockatrice, Chimera
- Honor stage: Phoenix, Hydra, Ghostbeard
- Epic stage: Swamp Kraken, The Roc God, Cerberus, The Dark Prince (2 forms)
All bosses are stronger than in the previous stages.
In older versions, there was an alternative with 7 rounds, where the last round has the boss.