Demons and Devils

Like the elder Titans, entities of primal urges made flesh by mortality's subliminal interaction with Anima, demons are likewise entities that are willed into being by belief. Demons often represent and are the personifications of humanity's fears, darkest desires, and wickedest impulses, though some gods also embody or experience domain overlap with such things. Philosophers heatedly debate the differences between divinity and infernal natures with some of the most preeminent minds ultimately asserting that the distinction is one of origin: a god is a god not because it is inherently good but rather because it originates from Nyktheon while a demon is a demon not because it is inherently evil but because it originates from the infernal realms, locations associated with nightmares and mortal terrors. Demons, though, due to their origin in the infernal realms, often experience an enfeebling effect upon entering the mortal realm—though this is not to say that they are not still deadly threats in their own right and far more than any single average mortal can take on—and thusly tend to remain in their own realm. That being said, demons delight in corrupting from afar, whispering dark secrets and forbidden knowledge into mortal ears and breaking their weak minds with madness and murder simply for the pleasure of the act more often than not. In this way, demons help to produce devils.
Devils, unlike their more powerful and ancient predecessors, used to be mortals. Some are merely souls corrupted by the taint of demons while some are foul souls who can't let go of the miserable lives they led. Having been despicable in life, these spirits fester in death and their punished afterlives. The worst of these hateful dead, through ages of bitterness, gradually transform into fiends recognized by the people of Etheria as devils.
The lingering mark of fiends on the mortal realm can be seen in the presence of some Cambions, humanoids who are born from exposure to extraplanar energy, irradiation from the energy of the infernal realms being one such type. Though some cambions may possess something of a fiendish heritage due to this, these cambions are not inherently evil peoples. Like any other humanoid, they have the potential for great evil and great good.