The word “demon” is a bit misleading, since it gives the impression that they consist of one coherent group. This is far from the case; all researchers agree that there are (at least) two major subdivisions:

Demons of the Void and Demons of the Essaence. Demons of the Void include the demon type most often summoned by brave (or fatally ignorant) spell users: Demons of the Pale. The Six Pales are believed to consist of wildly different topologies and environments, but they are still relatively close to human conceptions. It is possible to communicate and strike deals with the inhabitants, but the first mistake is often the last in these deals.The less it is said of the Demons Beyond the Pale the better, these dark entities are powerful beyond belief.

The Demons of the Pales are somewhat comprehensible, but the same cannot be said of the other inhabitants of the void. The Older Ones, as they are called, consist of myriad different subgroups. Some of them mockingly mimic normal forms,while most of them are more comfortable in their natural form (of which the normal-planar projection is invariably hideous to human view).

The Void is also “home” to a vast number of other intelligences, whether one calls them Demons or not is irrelevant. At times a Flow Storm or some other major disturbance can open a brief gate to one of the planes of the Void. Fortunately these events are rare, since they rarely leave survivors.

Demons of the Essaence, on the other hand, are deadly creatures inhabiting the Chaos Planes unpredictable and cruel, they are extremely hard to deal with, since they often follow no comprehensible motive. Summoning these beings is dangerous, and controlling them is even more so. Most spell users leave them alone. The Ordainers are among the most powerful of the Demons of the Essaence.

The Chaos Planes are believed to be linked with the Dark Gods though there is no conclusive evidence.

Lucky for the inhabitants of the “portal”, Myaasia, all beings are weaker when out of their own place, thus any outsider is weakened greatly.

The greatest heroes of Myaasia are thus more than match for even the strongest demons when on this plane. This does little to help the poor villages or such on path of such a demon summoned by someone when no great hero is nearby