Dark Creature

Be wary of the dark, for those who cannot see the darkness, cannot resist it's temptation, and are thus forever stained in black. A species of shadowy spirits, that are considered the opposite of Nymphs. Dark Creatures exist on the plane of Abaddon, but can travel between planes as long as there is darkness. They exist in a shapeless form at their most basic level, but can gain shape through the use of mana, usually taken from living a host (by eating the host). Most dark creatures are soulless and because of that are unable to hold mana within their own bodies. They require constant subsistence (usually by feeding on living things) to retain mana, more powerful dark creatures (Revenants/Eidolons/Shadows) can generate their own limited mana and those with souls can retain it. Dark creatures can reside in any dark place, but are notable for being mentioned in the Tales of Eclassia.

Origin
Dark Creatures are created when a soul is a tainted by darkness, as the darkness consumes the soul more and more they become weaker and weaker until their soul ceases to exist. When a soul is consumed by darkness it separates into two parts, the Light Soul and the Shadow Soul. The Light Soul represents the original soul and is slowly depleted until it is completely gone. The Shadow Soul represents the darkness within the soul and begins to deplete when the Light Soul is gone, unless it is sustained by mana.

Types
Ranked from Weakest to Strongest, the stronger the dark creature the more presence of a soul it has.
 * Dregs - Mindless and function on animal instinct.
 * Shade - A low ranking Dark Creature, serve as the working class and lower class soldiers.
 * Wraith - Middle rank of Dark Creatures, serve as the more powerful soldiers.
 * Revenant - a High ranking Dark Creature.
 * Revenant Duke
 * Pureblood Revenant
 * Prime Revenant
 * Shadows - A Dark Creature that has taken the form of a humanoid being, they are more powerful than Revenants and can move about in the day light. An Eidolon has the ability to make a shadow clone of themselves. All Resonators, Reasoners, and Replicants are Shadows that reject the Eidolons.
 * Pureblood Shadow - Shadows created from Eidolons, they are more powerful than every other type of Shadow.
 * Twilight Shadow - Ascended Shadows, some can rival Purebloods.
 * Reverse Shadow - Revenants that have turned themselves into Shadows (Eidolon's cannot do this because all of the original Eidolons were not born as dark creatures.
 * Other Shadow - Shadows created from a human, not through experimentations, when exposed to the Realm of Shadow. (When a human is exposed to the vast darkness in the air of the realm of Shadow, it is theorized that their soul splits into two, one being a Shadow's Soul and the other their own.)
 * Neoshadow - The rarest kind of Shadow, they are created naturally by the darkness of the Realm of Shadow, most are formlessly and take forms based on the first living-non-Dark creature they see.
 * Belshadow
 * Eidolon - Legendary Dark Creatures heard of mainly in the Tales of Eclassia.
 * Lesser Eidolons
 * Greater Eidolons
 * Eidolon Lords
 * Lords of Shadow - Mythical creatures said to be the origin of all Dark Creatures.

Note

 * To explain it simply dark creatures can be said to be the closest to real evil there is in The World (aside from faceless), because it is the corruption of a person...