Demons

Unlike devils, demons are said to have always existed, long before the Divines, perhaps even before the Prime Elementals. Whether they always had their current form though is unknown. What is known though, is that destructive beings of chaotic evil have existed as long as any good or order has existed in the Underworld or Mortal World, perhaps to create cosmic balance.

There are at least 100 times more demons than devils, however, demons constantly destroy one another and usually attack as mindless hordes, unlike the disciplined armies of the Nine Hells, thus preventing them from wiping out their rival or gathering enough to destroy the mortal world

The closest thing to "order" to exist among the demons is the rule of power, and the only control powerful demons have over their "servants" is through fear alone. Yatath, as a fallen Divine, is simply the most powerful being in the Abyss (and even this is uncertain), and thus, he is able to steer them in the direction of his goals to some degree.

Since demons do not have a hierarchy in the way the devils do, powerful demons are constantly born and destroyed, and there might be thousands of demons who have made pacts with mortals, only to be wiped out and replaced by others shortly after. '

There are however, a few who are powerful enough to have survived through millennia.