Ghoul

A ghoul is a disembodied demon that can possess a human corpse to eat living, human flesh. Despite being essentially vile and ravenous, their intelligence and craftiness rivals that of humans and other demons such as vampires and werewolves, making them one of the most powerful and dangerous demons in the series.

Characteristics
The eyes of a ghoul have black sclerae and pupils with white irises. The human corpse ghouls possess stops decomposing and is restored to tiptop condition. When taking possession, large and thick black veins spread throughout the body at a slow rate until the skin turns comepletely black like charcoal, resembling a three-dimensional black sculpture with its eyes still the same. This is called a ‘Complete Ghoul’ which retains most of its supernatural abilities while having their demonic possession become permanent. Coupled with intelligence, ghouls are one of the most dangerous demons in the Blackbird Universe. Upon getting killed, ghouls, along with their vessel, combust and burn to ash. If a ghoul decides to leave their vessels behind, it will also combust. In their true amorphous forms, ghouls cannot be killed by conventional or supernatural weaponry, but they can be controlled using magic or be captured and used as killing machines, as demonstrated by the Phoenix Organization and their army.

Before Blackbird
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Blackbird
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Powers and Abilities
Possession: Ghouls can possess a human corpse as their vessel so that they can interact with the physical realm and eat living people; however, they can leave their vessel if they so wish, but doing so turns said vessel they took into ash instantly. Once a ghoul has possessed a vessel for a significantly long period, they become a ‘Complete Ghoul’, or a ghoul who has a permanent vessel and can use most of their original powers. In this form, the black veins that appears on their vessels skin will slowly spread the longer they inhabit the corpse until they cover the skin to make it as black as charcoal, making their possession permanent and restoring different powers and abilities, including:
 * Amorphous Form: Ghouls are incorporeal demons whose true form is an amorphous darkness that cannot interact with the physical realm, and vice versa, unless they possesses a human corpse. Their diet is only living human flesh, but to feed they must possess a human corpse to do it.
 * Immortality: In their true form, ghouls are truly immortal as they are impossible to kill by any means unless they possess a human corpse, or ‘meat suit’ as ghoul’s call it, which leaves them completely vulnerable to attack and even death.
 * Intangibility: In their amorphous form, they can and will always be able to pass through solid matter. Complete Ghouls, however, cannot use this power as their vessel intereferes with this ability.
 * Flight: In their true forms, ghouls can fly at various speeds, especially as a way to escape their vessels before they are killed. Complete Ghouls still have this ability, albeit for limited durations.
 * Superhuman Strength: Ghouls provide their vessels with superhuman levels of physical strength. They can overpower even the most aptly-trained humans. They can knock down trees in their path, shatter limbs with a punch or kick, and even bend or smash metal and steel with their bare hands.
 * Superhuman Speed and Agility: With their vessels, ghouls can move faster than human eye can perceive, appearing as a blur of motion to the naked eye. They are fast enough to dodge bullets and traverse water and vertical and upsidedown structures with pure speed.
 * Superhuman Durability: Ghouls’ vessels are near-impossible to inflict damage as most projectiles ricochet off their skin and most conventional weaponry will either break or deflect off their flesh upon contact. Their bodies are also tough enough to absorb or even sustain damage. Only magic and more divine/holy weaponry, like silver that is blessed with a sacred prayer, are the only things that could harm ghouls physically. In their forms, however, none of these things work against them as they are an intangible darkness.
 * Enhanced Senses: Ghouls possess senses more acute than mortals. They are able to smell their prey and track it from several kilometers, hear a single footstep without the owner of those sounds being within their line of sight, and feel the slightest change in atmosphere and react accordingly.
 * Amorphous Form: A ghouls’ true form is an amorphous otherworldly substance which is black in center with silvery tips and edges. It is immune to conventional and supernatural weaponry. This form, however, cannot interact with the physical realm, let alone eat living things, so they must possess a human corpses to do this. In this form, ghouls also possess:
 * Shapeshifting: Only Complete Ghouls can change, at will, the forms of their vessels into their true amorphous forms interchangeably. They can even manifest their true amorphous form along their physical vessels to either defend against attack or to escape.
 * Mental Manipulation: When they are seen in their amorphous form, or if a Complete Ghoul manifests or changes into it at will, ghouls can scare mortals into complete shock and become permanently catatonic until that said ghoul is destroyed.

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Trivia

 * In pop culture, the term “ghoul” is often used for an undead creature that eats freshly buried corpses; however, in Blackbird, ghouls are demons which possess a human corpse and eats only live humans, coining the term ‘monster’ or ‘unholy one’ by most demon hunters.
 * In Islamic lore, actual ghouls are not always dead but instead are often depicted as a devilish form of djinn or demon, believed to be sired by Iblis which consumes the flesh of the deceased and sometimes robbing a tomb or grave to get what they want. In Rodriguez’s version of ghouls, they possess more intelligence which makes them even more dangerous and that in their true form they cannot be killed so demon hunters must act quickly to subdue and slay the ghoul while at their most vulnerable.
 * Although never stated in the series, there is a possibility that they are related to the equally terrifying wendigo. The reason is that their method of using demonic possession for the express purpose to consume living human flesh is nearly identical; however, ghouls are disembodied demons whereas wendigos are demons which are created when a human commits cannibalism for any length of time.
 * Complete Ghouls are ghouls who have possessed a corpse long enough to permanently inhabit it, and that has eaten enough humans to gain enough strength to restore all of their supernatural abilities; however, this is rare as this can only happen after being inside of a human corpse for a significantly long period (the duration is depends upon the corpse they inhabit and how hungry they were when possessing their vessel).