A undisclosed civilization has been having an issue with their sewer system. Plumbers were sent, and haven't returned. Ominous groans have been heard that shake the foundations of the buildings. The people are freaked out and have sent a distress signal to anyone that could possibly deal with this mysterious ordeal. Since huge monsters will soon be a thing, I thought a mission could benefit with customized giant po golems or maybe even something more sinister and raunchy to deal with. Namely, The Clog; a massive conglomeration of flushed items (not necessarily all biological waste) that is quite resourceful with it's various appendages of volatile objects and living (or once alive) things. Something that'll make you go " ohh No No No, that's just nasty." and progressively go into "NOPE! NOPE! This needs to die! DON'T TOUCH ME!" Some players may argue and disapprove of how a grand and messy boss battle such as this would be a little too excessive in nature, but I feel that if you're going to be in an active alien sewer, that's just what you would have to risk dealing with. As for the reward, I'm sure some players might be shaken up a little in disgust, so maybe something nice!
It must have the Gas Belch, Fly Swarm, and Fish Spray attacks. Because those things attacks are just nasty. I could see it as a large sort of "immobile" boss that basically occupies one wall of the battle arena.
