demon

Demons are twisted creatures that dwell in Hell and act in opposition to the gods. They are present on any realm which has native inhabitants. They attempt to devour the souls of both living and deceased mortals, growing in power as they do so.

Origin

Demons arise from two main sources. The first, and most well known method, is through direct transformation of a mortal soul into a demon. While most mortal souls pass into the afterlife soon after death, in some circumstances the soul will remain in the land of the living as an incorporeal ghost. If these ghosts linger for too long they will succumb to frustration and despair at being unable to move on causes them to transform into a demon and transmigrate to Hell. However, this is a fairly rare occurrence, happening to relatively few people and taking several years to complete.
The more common, and less well known method, is when a mortal experiences certain strong negative emotions represented by the antielements such as despair, prejudice, or misotheism or commits certain heinous crimes like murder. This does not create a demon itself, unless the emotion is particularly intense or crime particularly great. Instead, each occurrence creates a small amount of pneuma in Hell, which accumulates until an entire demon is formed. Because most mortals are unable to witness this process, few know about it.
Other methods of demon creation exist, but they are fairly rare. A particularly wicked individual may transform into a demon through the sheer collection of malice. There exist some powerful magics that can allow a person to willingly transform into a demon. Those who transgress against a god may find themselves transformed into a demon as well.

Evolution

Rampaging Gibberling by Denis Khusainov

Gibberlings

Most demons begin existence as a gibberling. These mindless creatures are driven by a desire to devour the souls of mortals, attacking and killing the living and consuming their souls before they have a chance to pass on. As gibberlings mostly hunt in packs, they typically rip a soul to shreds, only eating a small portion of its pneuma. However, once they consume roughly the equivalent of one mortal soul, the gibberling regains a small measure of intelligence and cunning. While still animalistic, the awakened gibberling is able to more directly target prey and devour them. It also becomes opportunistic, cannibalizing other gibberlings who are injured.
A single gibberling is not a large threat, being roughly as dangerous as a small wolf or other medium-sized pack hunter. However, gibberlings are rarely encountered alone, instead traveling in packs to attack and take down prey. They swarm larger prey, pulling it down and slashing it with their razor sharp claws and teeth.
Eventually, the gibberling has consumed enough pneuma that it regains a mortal mind. This mind is formed of all the most negative aspects of the souls it has consumed, giving it a cruel, malevolent intelligence and the desire to grow in power. At this point, the gibberling transforms into a drude.

Drudes

Drudes are intelligent demons composed of the devoured souls of dozens or hundreds of mortals. Much like gibberlings, they are primarily driven by a desire to feed and devour further mortal souls. Unlike gibberlings, drudes are mostly solitary, refusing to work with other demons because they do not wish to share their meals with others. On occasion, they will corral a small number of gibberlings to help them take down larger, more dangerous prey, then devour both the prey and the gibberlings.
Despite their intelligence, drudes are still mostly violent, singleminded creatures, relying on their brute strength to attack and overwhelm victims. They rarely make long term plans or engage in attempts to corrupt mortals.
Once a drude has devoured enough additional pneuma, it will transform once again, into a daeva.

Daeva

As opposed to the drudes and gibberlings before them, daeva begin to vaguely resemble the mortal creatures they are mostly composed of. A daeva composed mostly of humanoid souls will have an upright stance, two arms, and two legs for instance, though with a monstrous visage which gives away the truth of its nature. Daeva develop their own unique personalities and regain the ability to think long term, plan, form alliances with other demons, and use lesser demons in their schemes.
Daeva begin actively involving themselves in the mortal world, answering the summons of conjurers, whispering temptations into the ears of mortals, and offering minor boons in exchange for souls. At this point, daeva tend to discover what negative mortal emotion they will embody, such as rage, hatred, lechery, narcissism, or sadism. Their primary goal remains to consume souls, though they are not nearly as single-minded as their lesser forms. They tend to target souls with richer pneuma, such as those who have gained experience in the world and possess some amount of knowledge, wisdom, or skill. They will also devour the souls of drudes, other daevas, and greater demons that are weakened or injured when the opportunity presents itself.
Upon consuming enough pneuma, the daeva will again transform into a erebian.

by Denis Khusainov

Erebians

When transforming into an erebian, a demon is allowed to shape how it appears. Due to this, erebians are fairly unique, with no two possessing an identical form or appearance. These forms are often chosen based on what emotion they embody to better draw it out of mortals. For instance, a demon that embodies lechery may appear as an exceptionally beautiful mortal, while a demon that embodies hatred may appear as a shadowy creature with serpentine features and poison-tipped claws. Once an erebian has chosen its form, it cannot change until it evolves further.
Erebians tend to rule over their own minor demesnes in Hell, coercing lesser demons into serving them. Demons of this rank rarely feed on lesser demons, though they may devour the pneuma of a greater demon if an opportunity presents itself. Instead, they target individual mortals of great renown, virtue, or power and tempt them. Erebians are the weakest class of demon able to directly offer power to mortals, granting access to their demonic powers in exchange for portions of the mortal's pneuma. This way, the erebian slowly devours the soul of the mortal, eventually dragging them down into Hell before devouring them completely.
Erebians can eventually evolve into gehennans.

Gehennans

Gehennans are also known as demon lords and rule over large swaths of Hell. They force other demons to serve them, offering up small amounts of pneuma in exchange for the lesser's loyalty. They often use these demons as agents in the mortal world. A gehennan will not hesitate to devour the pneuma of a demon who fails it, though the pneuma of lesser demons do little to feed a gehennan.
This evolution tends to be a more extreme version of their previous form, often manifesting physical effects on the reality around them due to their power. For instance, a demon embodying rage might make mortals in their vicinity begin committing violence against one another. While lesser demons tend to travel to the mortal realm occasionally, either to hunt or through summoning rituals, gehennans rarely venture out of Hell on their own volition. Instead, they appear to the mortals they wish to tempt via dreams or mortal agents.
Gehennans can provide power to mortals who form pacts with them, endowing them with powerful abilities at the cost of the user's soul. They can also grant wishes to petitioners as long as it is related to their embodied emotion. Demons of this class begin to seek out mortal worshipers, masquerading as gods. This worship not only generates pneuma which feeds the demon, but also draws worship away from the true gods, generating more pneuma within Hell. Gehennans are able to absorb the pneuma from the evil deeds committed by mortals they tempt.
The exceptionally rare gehennan can eventually become a dudael.

Dudaeli

The dudaeli are the highest class of demon, also known as demon kings or demon gods. Most Hells only have one or two, some have none at all. The nature of the dudaeli prevent more than a handful from existing in each Hell, as they compete for pneuma with each other. While they may not actually fight each other, their needs for pneuma ensure that only a few are capable of existing at one time. Dudaeli often command gehennans, treating them much as a king would treat his counts, though will often devour any gehennans who get too close to becoming another dudael.
Dudaeli tend to be the most frightening and awe-inspiring of all the demons. Their forms are often massive, towering over mortals, larger even than ancient dragons and titans. Dudaeli alone cannot be summoned, even by the most powerful conjurers. In many ways, a dudaeli is just short of a god in power. They frequently have worshipers and offer them power much the same way the gods do. The difference is that the followers of dudaeli do not go to the afterlife when they die, but rather are devoured by the demon to feed them.
Dudaeli that fail to receive enough pneuma will eventually revert to a gehennan.

Powers and Abilities

Lower class demons posses very few unusual abilities, mainly relying on physical strength to kill mortals and steal their souls. Gibberlings rely on numbers to hunt, while drude rely on brute strength. Daeva and higher class demons possess increasingly powerful magic, though their exact powers can differ greatly based on their embodied emotion and chosen forms.
The one power shared by all demons is the ability to nearly instantly return to Hell called transmigration. Gibberlings utilize this instinctively when they first form, but rarely use it otherwise. Drudes and higher class demons can do so at will, unless bound in place by a summoning circle. This power only allows a demon to return to Hell and offers no other usage.

Killing Demons

Demons, as with all creatures, can be killed. Gibberlings can be harmed by even mundane weapons and some large animals have been found eating dead gibberlings. Drude are heartier, able to quickly heal all but the most grievous injuries sustained by mundane weapons. Magic and enchanted or blessed weaponry inflict wounds that do not heal, allowing them to be dispatched more quickly. Daeva and higher class demons become progressively harder to kill, able to regenerate from nearly all wounds, resist various forms of damage, and even recover from wounds that would be fatal for most. Gehennans have been known to survive decapitation.
All demons have a weakness to fuliginous and nivose energy, with exposure preventing their ability to heal for extended periods. Enough energy can even destroy demons outright, though the amounts required to do this to gehennans or dudaeli is immense. Individual demons may have specific resistances or weaknesses depending on their chosen forms and embodied emotions.
When demons of the daeva class or higher are destroyed, a large portion of the pneuma composing their bodies transforms into gibberlings, which are starving and almost immediately turn on one another in a frenzy.

Risen Demons

As opposed to fallen angels, which are virtually unheard of, risen demons are a well-documented phenomena. While certainly not common in any sense of the word, at times a demon will come to reject its malicious and evil ways. Oftentimes, this happens to the most heinous of demons, those who revel in devouring the souls of pure-hearted mortals. At times, the morality of these souls will manage to break through the demon's personality and cause them to develop a conscience. Other times, a demon experiences a positive counterpart to the emotion it embodies (such as love from lechery or hope from despair), which awakens other positive emotions in it.
Often such demons, so disgusted at their own actions, destroy themselves out of self-hatred. Occasionally, though, they decide they must repent and redeem themselves. In such cases, the demons rip out their own demonic heart and discards it. The empty void is replaced with fuliginous and nivose energy, transforming the demon into a deva. They reshape themselves once again, gaining a form that looks mostly like the mortals whose souls they have devoured, though always with some trait that marks them such as horns, cloven hooves, or batlike wings.

Type

Metaphysical, Demonic