Acrid

How to unlock: Acrid is unlocked by defeating him in the Underwater Catacombs, 3rd stage. On the topmost land layer, above the water, there is chance for a box to spawn on the rightmost side. Opening the box will spawn Acrid.

Acrid deals huge amount of damage after stacking poisons from his Festering Wounds, Caustic Sludge, and Epidemic. Try to stun targets inside your Caustic Sludge for maximum damage. Remeber that you can fight at melee and range!