Invisible Frog (who is actually transparent, and appears to be a goblin) is the boss in Epic War 3's Cave of Trial 5. Beating Cave of Trial 5 does not unlock Invisible Frog, but awards the Bezerker Spell. The Invisible Frog is the most powerful boss in all of the Epic War games.
Epic War 3Edit
In Epic War 3, Invisible Frog in not unlockable and is the boss in Cave of Trial 5. Invisible Frog is invincible, and does 1 hit K.O. for everything (even your castle). The idea is to keep him pushed back or stunned so that you destroy the castle before he kills you. Like all other units he appears to die once the castle is defeated. In the mobile version of game his appearance is changed from being a normal sized but transparent black Goblin in the PC version to being red and slightly bigger than an average Goblin.