The Stupid is the Embodiment of Evil, and predates the birth of the Fictosphere.
The Stupid assisted in the birth of the Fictosphere, and went on to shut Deity Guy off from the Fictosphere's gestation. This resulted in all the beings in the Fictosphere trying to kill each other, which suited the Stupid just fine. They then decided to stay out of things.
The promise was upheld until they appeared to Subject M in a hallucination, setting him on his quest. This led to the Stupid trying to destroy Subject M. He did not interfere again until quite recently, meeting on a neutral plane and forcing Antwon and Baco to battle.