Demonology

This page is meant to explain the intended functions of Hell and Demons in several parts. This information is specific to the Standard Universe.
== Demons, Mortals, and Those Beyond ==
Mortals have many theories on the workings of demons, but scant few truly understand their underlying mechanisms. First and foremost Demons are native to Hell, and no other plane. The existence of a demon without is considered an anomaly, and typically a worrying sight. They typically do not have leave to meddle in the mortal planes without specific instructions to do so. A common myth perpetrated among even the well versed is that Demons take souls, this is inaccurate.
A demon can no more take a soul than they can create one, instead, the individual is Marked by a demon. The exception to this is if in no uncertain terms, an individual surrenders their soul willingly and knows what they're agreeing to, though a spark must remain or this effectively just kills the target outright. Mortals however who have been Marked encounter a fate about as terrible, for the process of being Marked effectively starts a slow decay that will lead to their soul stagnating and their spiritual mass becoming a demon. This is the point of confusion, as the spiritual mass is not 'lost' but changed to an inert form not detected as a soul. 
Demons cannot freely help mortals, as this is not their intended purpose. Instead, they are meant to offer pacts and deals, often skewed in the demon's advantage. The only way to get a deal outright beneficial is to know two parts of a demon's name, as well as their Title. To completely bind a demon to one's will requires all three parts of their name and their title. As for their purpose with mortals, they are by and large a means to promote growth and change and punishment of severe spiritual decline. For this purpose, there are often 'Great Calms' and 'Great Perils' in recorded history of a rising and a fall of Hell periodically. The present age is considered a Great Calm, but recent history has indicated Hell may be stirring, and dark days may eventually be upon us.
There are more secret roles of Demons, pertaining to their unique authority 'Hell Fire'. This is the expression of the Divine Power bestowed to Hell and all who call it home. It is used to expedite the processing of Souls in the Underworld by punishing those deemed too wicked and dark by painfully, violently stripping a soul of its elements, purifying it for rebirth after an appropriate period of time. Their contributions have fallen off of late, not helping an already overburdened Underworld's plight. 
Beyond this, Demons are bound to defend reality from unnatural occurrences, and the hordes of Hell will march if an intruder is detected from another reality, or that of things beyond that should not be. Hellfire has no natural immunities in or outside of the Standard Universe, making it incredibly difficult to disrupt it beyond a certain threshold and offering more stability than some universes. Only incredibly strong entities can even passively resist Hellfire, and any among that number will not go unnoticed by the greater forces of reality, especially if Hell's response grows strong enough.
In addition, entities that may be considered native to the Standard Universe may trigger a demon to respond with full force if they are deemed equal threat or anomalous as those beyond the bounds of the world, requiring those with unusual qualities to stay out of the affairs of the demonic or find themselves in an unfavorable situation.
== Types of Demon ==
Demons come in different kinds, but it is difficult to know their exact numbers due to Hell being notoriously lacking in hospitality.
* Pride
* Violence
* Greed
* Envy
* Cubi (Succubi and Incubi) aka Lust
* Sloth
* Atrocity
==== Princes ====
Mysterious, unknowable, and the masters of Evil in the universe. Their power isn't known for certain, but there are reasons why Hell has never been toppled, even by the most well meaning of beings of power: few may boast strength capable of even phasing the Princes of Darkness, and even the bravest hearts know true despair before them. Many a hero descended into the dark heart of Hell only to become their newest Duke.
==== Dukes ====
Those truly with power within Hell, those who in the presence of, Demonlords forget any notion of power or pride and know what it means to feel fear. Hand chosen by the leader/s of Hell, the Dukes command the Circles of Hell themselves. Having long ago gained their own souls, these demons stand tall with the might of Minor Deities. So terrible and calamitous their presence is, that Hell itself will chain and drag them back should they ever threaten to emerge in the mortal plane.
==== Demonlord ====
Creatures born of legend and nightmares, these creatures are great and terrible and possess unbridled power. Holding territory within the vast darkness of Hell, these tyrants squabble and bicker for what are ultimate scraps of true horrors. They possess and lead large armies of Elders and Lesser Demons, and often are the antagonists of many a tragic tale. Behind their machinations however is the will of a greater threat...
==== Elder Demon ====
Typically occurring around 200-300 years of life, these are cognizant demons but lack souls. One might even be fooled by some of these into believing they are more than what they seem, but this is foolish and ill advised to ever assume. The average human could never hope to survive even a glancing moment in their presence. Stronger mortals can fend them off with great sacrifice.
==== Lesser Demon ====
Devoid of will and intelligence, the seeds of which do not manifest until at minimum, 100 years of existence. These can be dealt with by average mortals with proper equipment and planning.