Quagfing floats through the air, releasing a thick, polluting smog. It lacks any malicious intent in this; it is simply oblivious to the toxic nature of its own gasses.
Getting up close to a Quagfing will give you a chance to observe, through its thin skin, the toxic gases swirling inside. A Quagfing hunts by leaving its mouth wide open in water and waiting for its prey to blunder in.