Story-related; unlocks for defeating the Gruesome Twosome mini-boss fight in the DLC story mission, ‘Shit Hits The Fan’.

The Clotter is basically a mini version of The Dirge that can teleport around the area. The have a couple basic attacks where they charge at you and a ranged attack where they shoot a constant stream of blood in one direction. Simply avoid their attacks and lay into them with your best weapons and fury mode like any other zombie. They will become recurring special type enemies throughout the rest of the DLC from this point.