The Abyss

Where the devils of The 9 Hells represent primal Law and primal Evil, the demons of the abyss are the incarnation of primal evil and chaos. They embody all that is gruesome and chaotic, and the abyss itself reflects this. Though it is known as 'The Abyss', it is infact an infinte gathering of layers, each ruled by it's own demon lord. These layers appear to appear around particularily powerful demons and dissapear with them, meaning that as long as there is a demon lord there is an abyss.
The demons seek to concquer the world, but unlike the devils they are not united. Each demon lord have their own goals and methods, and rarely do they work together. They do not either have armies, just hordes of varying sizes that ravage whatever they come across. More powerful demons may have the intelligence to gather warbands, forcing lesser demons into their service through displays of power or tricking mortals into doing their bidding - though unlike devils they are not obligated to keep their end of the deal.