The illustrated Bestiary of Creatures starting with the letter...

Rot

The Rot is made up of various decayed corpses being held together by putrid slime that forms a decaying rotting blob. This creature can also be in the form of a disfigured skeletal stem or a sludge pool. They emit a foul stench and like quicksand, can seize and devour its victims. The Rot can secrete a deadly acid spay at its victims. Do not poke it with a stick!