Wrath of the Righteous
A demon lord is a very powerful and unique demon. They are by definition rulers of at least one layer of the Abyss, and have hordes of lesser demons in their service. Being creatures of chaos, however, not all demons are servants to a demon lord. As the Abyss is nigh infinite, so too are the number of demon lords.
All demons are created from larvae, the Abyss-damned souls of evil mortals. By amassing tremendous power and prestige, any demon can theoretically transform itself into a unique member of its species. These creatures have not yet achieved the full status of demon lordship, including demigod status, and are as yet somewhat unformed. They must continue serving more powerful demon lords until they come into their own. These creatures are known as nascent demon lords, and they exist in their hundreds or thousands in the Abyss. Of this large population, however, very few survive the trials and tribulation of the Abyss and its denizens to ascend to full demon lordship.
All demon lords are technically—if not actively—at war with one another almost all the time. While some alliances are forged and uneasy truces held, most demon lords are actively at war with one or two others. Often these combatants have similar interests (and are therefore rivals for mortal worshipers), or have adjacent layers.