The volcano explosion originated a ball of destructive energy and unleashed a wave of fire that extended for hundreds of thousands of meters.
The wave immediately reached the place where both devils armies fought and had more than enough power to reduce Rank 4 life form to ashes.
Just when the flames were about to consume more than five hundred thousand devils, the eight Marquises positioned themselves in front of their soldiers, and they used their consciousness to form an invisible wall that stopped the wave.
Both sides worked together not because they care about the lesser devils but because their burdens would be greater in the subsequent battles if they are gone.