When you get here, your first sight is likely to be these most welcoming stinky creatures called Stinkblobs:
Although what you are looking for is a placeholder called
Deep Artery Valley - 1300x2330
Rot Plague appears to be on a 20 minute spawn timer, and also seems to have about a 20% chance each 20 minutes or thereabouts to spawn the stinky creature you are looking for.
When you have killed Rot Plague and triggered the spawning of The Pest you will be faced with a level 200 creature and his friends.
The Pest Pus can be a little annoying to say the least, more and more are spawned by The Pest, but with a little skill on your part we are certain you will be walking away with some of the above items really soon!