In the Abyss, in all the nine floors of the realm of pure darkness roams creatures that are not demonic nor sentient. These are called Paragons.
The Paragons are creatures that were born from pure evil and they created their own society. Even the Forsaken who rules the entire Abyss has little control over them. Instead of taming these creatures, he let them wander around the floors and maul every demon they see.
The Forsaken loved chaos, and the more suffering in the Abyss was, the more powerful he gets. As he let the Paragons do what they want, he didn't realize that they had developed a human-like minds. They could now communicate and some are sentient.
He was not expecting this until the leader of the Paragons, King Paimon, entered his castle. King Paimon wanted his child to experience life in Terra, the realm above them. The Forsaken did not think it through and agreed.