Demons of the Outer Dark

Outside the Aether is just black, empty void. Not even air to breathe.

By Agostino Arrivabene

No. That’s wrong. It only seems that way because of your primitive instruments. You know, the ones rolling around inside your skull.

Out there is primordial chaos. The monsters that the gods cast out before time began. Call the tiniest whisp of that stuff into the material plane, and it congeals into a corporeal form known as a demon. Being forced to take on a material body appeals to it about as much as being pressed through a red hot sieve appeals to you. It reacts to your summons accordingly. That’s just one reason why you’d be wise to keep the thing contained with strong magic.

Ades Pantocrater - Agostino Arrivabene

Magic circles and the like are often effective just because they’re a complex, orderly geometric pattern. Any kind of organized structure might be sufficient to send the demon’s physical form into a crash state. Or maybe not.

Killing the physical vessel doesn’t free them, though it might disperse weak entities enough that they can’t reassemble their physical form.

They must be banished with tools mortals cannot create themselves (certain rituals and items handed down by transcendent entities, cleric spells). The disintegrate spell also annihilates demons permanently, creating a small amount of Black Aether*.

It's hard to say whether demons exist as discrete entities outside the material universe, or if their individual nature manifests only when drawn into our world. It's possible that the ritual and the sacrifice itself is what shapes raw chaos-stuff into a physical form.

While their powers can be terrifying to behold, they are summoned and tormented most often for knowledge. Their realm exists outside and throughout the material universe. It's likely they know more than the gods themselves.

http://www.agostinoarrivabene.it/paintings/

While a demon may take on numerous forms, and manifest subtly different powers with each summoning, it's one pleasure on the material plane is to degrade order into disorder. Set loose from its bonds, it endeavors to turn families into broken individuals, orchards into ashen waste, and kingdoms into chaotic orgies of death and destruction followed by silence.

It has no name, but you can be certain it will always remember you. It's fondest wish is to return the favor of its summoning, and bring you home as a souvenir.

*(I don’t know what that does yet, but it will probably be something like a metaphysical version of this. Highly reactive in unpredictable ways, with precipitates that might have a variety of effects on the material world).