Concept

Deities
Highest form of a spirit, and only 4 of them exist. They are the dominant authority of the Abyss. They are the only spirits that have a physical form of their own in the mortal world. The deities can take the form of other things like smoke of fire. They never had a soul, or a necessity to have one.

Elementals
These spirits were created from nature, and exist within things like rivers, or trees. The existence of elementals is fleeting, and they perish as soon as they come into existence. Only a handful of elementals are as old as the deities and remain in reality. They never had a soul, or a necessity to have one.

Seraphs
The seraphs are spirits appointed by the deities themselves to become guardians to the balance of the Abyss and the worlds connected to it. They allowed their soul to ascend with the help of a deity. They do not have a physical form, and thus must find a vessel if they wish to exist in the mortal realm. They must get permission to possess.

They are divided into three types, depending on the deity that had ascended them. Omnis refuses to ascend anyone, and thus does not have a branch of seraphim of his own.

Lucifer
He was Omnis’ one and only Seraph, and the only Seraph to have never been a human spirit formerly. He found that souls make him stronger, and thus ascended to a higher being almost at the level of the deities. He is the authority over an area in the Abyss called the infernal regions. He commands an army of demons that go out into the mortal realm and collect souls for him, and consequently create more demons to be under his command.

Demons
Referred to as “the corrupted ones” by the deities. They are commanded by Lucifer. They come in different ranks depending on their spiritual strength as demons, also referred to as demonic strength. He has 7 commanders that each lead an army of demons. Each commander is responsible for a human sin. Most demons originated as demons, and thus are stronger, but some are created by human spirits losing their soul.

Humans
Born in their physical form, their spiritual form is released when they die. When they die, a reaper comes to take their spirit to the Abyss.

Exorcists
Humans who were given the ability to use the 12 incantations by the seraph Briathos under the command of Azrael, during the demonic uprising. The exorcist bloodlines exist to be able to protect humanity from possessions.

Revenants
Humans whose soul is stuck in their body, granting them a form of immortality, if they consume human blood. They die only to be resurrected shortly after. Drinking blood heals them, while also providing them strength, durability, and speed. They are often compared with vampire legends but are not hurt by sun or garlic. They do however lose their reflection, and thus do not appear in mirrors.To become a revenant, one must die with the blood of another revenant in them.

Eidolon
They are humans who were able to regain control after being possessed, pushing the possessor into the subconscious while still being able to tap into its powers. They are extremely rare, so rare that the last one to have been known of died 800 years ago.

Nephilim
Arguably can also be called a Cambion. They are children of men and deities. As deities have a physical form, they can bear children with humans. These children are born with unusual characteristics, like cat eyes or horns. Lucifer was able to bear one after gaining a physical form.