Epic War 1Edit
In Epic War 1, the Blue Dragon costs 2500 mana to summon, 20000 exp to unlock, and is your troop equivalent to the enemy's Red Dragon, that first appears in stage 6 of the game. It is recommended that you farm exp and unlock the Blue Dragon before you take on stage 6. It is also stronger then the enemies Red Dragon.
Epic War 3Edit
In Epic War 3, the Blue Dragon is unlocked by completing Cave of Trial 2, and the Blue Dragon appears in the battle with the final castle if the final battle is against Gald the Conqueror, or Abe Mukanaga.
Epic War SagaEdit
In Epic War Saga, they are called Sea Serpents, and have water element. For more information click here.