Ghoul
A Ghoul is an undead, immortal creature that maintains their life by feeding from corpses. They do not age and remain frozen in the moment of their death. A Ghoul cannot be born; they can only be created by their death and reanimation into a Ghoul.
Ghouls have also been called Zombies, although that is an incorrect term for most Ghouls.
A Ghoul appears as close to a Human as a corpse can get. They do still look like a dead body, so Ghouls have to be careful to keep up their physical appearance, especially in bright or harsh light. They are often heavy users of makeup and perfume.
Because they are a corpse, a Ghoul's body is in a constant state of decomposition. They deteriorate a little each day that passes, and take on more corpse-like characteristics as time passes, including unpleasant smell. Feeding restores them back to a full human-like state and removes the smell for a short time before the decomposition begins again.
They remain frozen at the moment of their death. Their hair and nails remain exactly the way they were at death and return to that state every 24 hours if any changes are made. They have no internal bodily functions but their external body can still be used as if they were still Human. It's what allows them to continue to live the semblance of a human life.
Despite being dead, Ghouls are not fragile creatures. For the duration between feedings before decomposition begins again, they are effectively superhuman. They have superior strength, are extremely resistant to injury, have dampened pain receptors, and have heightened senses that are so keen they can pick up individual scents and sounds from a mile away. They can also regenerate injuries from minor to near-fatal with relative ease, as long as they have an adequate food supply.
Zombies
Feeding is the only way to stop a Ghoul from decomposing. When a Ghoul goes an extended time without feeding, the decomposition of the body and the brain reaches a certain point as to where the Ghoul loses all control of themselves. They effectively blackout as the magic is the only thing keeping the Ghoul going.
In a desperate bid to continue its existence as it starves to death, the Ghoul becomes a mindless, ravenous Zombie, attacking anything living or dead it might be able to feed from. They are powerful and dangerous in this state, but the longer they go without feeding, the weaker they become.
If the Ghoul is able to feed during this time, they will regain consciousness and return to their human-like state as normal, with the physical condition healing back to the moment of death once again. The mental strain of such an event is rough on the Ghoul, and repeated episodes become harder and harder to heal from.
If the Ghoul is not able to feed during this time, they continue to deteriorate rapidly. Wounds will reappear, limbs can fall off, and the skin rots away. They eventually become too weak to function, and the Ghoul dies, reverting fully back to a corpse.
Ghouls are carnivores, specifically of the raw meat variety. The 'meat' they consume from corpses can't be cooked, and they can't eat any other food to keep up appearances. Attempting to eat anything other than raw meat makes them violently ill.
A Ghoul's primary food source is human corpses. The fresher the body, the longer that body can sustain the Ghoul until the next feed. They can feed on Human and Supernatural corpses equally.
They can also feed on any part of the corpse, though they have preferences for the brains. They do not have to eat the whole body in one sitting.
Embalming methods basically turn the corpses into jerky for a Ghoul. Not very tasty, tough to chew, but is still sustaining and can be fed on for a long time.
Once a body starts to rot, it can be used to feed on in a pinch, but it acts the same as rotting meat would to a person. It tastes gross and can make the Ghoul feel sickly. This also means they can't feed from other Ghouls, for the same reason.
Ghouls can feed on animal corpses in emergencies, but animal corpses can't sustain them like human corpses can. It can only stave off the inevitable starvation. A Ghoul would have to eat triple or quadruple the number of animal corpses to survive comparable to a few human corpses.
How often a Ghoul must feed and how much they must eat depends on the age and activity of the Ghoul. Generally a Ghoul will begin to decompose after one week and begin to starve after two weeks. Three to four weeks will have the Ghoul decomposing into a zombie-like state, mindless and ravenous. If the Ghoul is unable to feed on anything, they will starve to death and revert back to a corpse before the five week mark.
Frankensteining
The source of a Ghoul's magic rests in their brain. As a result, as long as the Ghoul's head remains intact, with the brain safely inside the skull, a Ghoul can survive catastrophic injury to their body. Even decapitation.
Thanks to a Ghoul's natural regenerative abilities, a Ghoul can swap body parts at will or even have their head reattached to a new body. This is referred to as Frankensteining, after Frankenstein's monster, a creature created from the body parts of other individuals.
In order to attach a new body part, the Ghoul must sew the new body part in place to where the original body part used to be. Then the Ghoul must immediately feed in order to heal the new body part to their body.
Once a body part is separated from the Ghoul's head, it immediately reverts back to a corpse state. It has no magic and no autonomy separated from the Ghoul. So if the Ghoul is separated completely from their body, they will need help being re-attached to a body.
When a Ghoul does decide to frankenstein themselves together, they can only replace the missing or removed body part. They can't add a third arm or a second head, for example.
Reanimation
Magic exists in the world to bring people back from the dead. While often considered dangerous, taboo, or the blackest kind of magic, it is possible to cast a spell or perform a ritual to bring someone back from the dead in a process called reanimation. If that kind of magic is successful, the person being reanimated returns to life as a Ghoul. It is impossible to return as anything other than a Ghoul.
A person can only be reanimated back into their own brain. The body can be replaced, since a Ghoul can feed and re-attach themselves to a new body. So can the head. As long as the brain belongs to the person being reanimated and has been inserted in the head, they can be returned to a new head and body.
A person can only be reanimated within two weeks of death. The brain can last a maximum of two weeks before decomposition is so severe that the magic will not take, as the brain cannot be brought back to life.
If the person has been preserved in some way - whether through science or magic - the decomposition can be slowed to give whoever is doing the reanimation enough time to bring them back. But preservation of either variety is imperfect, and only slows the decomposition, it doesn't completely stop it.
Reanimation can be performed by Mages, Unicorns, and Espers, depending on magical ability and powers, respectively. Reanimation can also be performed through a Merfolk's wish granting.
The Brain: The source of a ghoul's magic is in their brain. The only way to permanently kill a Ghoul in a way they cannot come back from, is to remove their brain from their skull and destroy it. As long as the brain remains intact within the skull, a Ghoul can continue to live.
Starvation: Starving a Ghoul forces them into a mindless, zombie-like state, where they crave flesh and blood, living or dead. Starve a Ghoul for too long and the brain deteriorates enough that it returns to a corpse-like state and the Ghoul dies. (As long as the brain remains intact, however, the Ghoul can be reanimated later.)
Fire: Because a Ghoul is a corpse, the body is quite flammable. If a Ghoul catches on fire, the flames spread quickly and are hard to put out. If a Ghoul becomes engulfed in flames and is unable to put it out or feed to heal the wounds, they will disintegrate and die. (As long as the brain remains intact, however, the Ghoul can be reanimated later.)
Acid: The same that is true of fire is true of acid – if left in acid, they will disintegrate and the Ghoul will die. (As long as the brain remains intact, however, the Ghoul can be reanimated later.)
Because a Ghoul is frozen in the moment of their death, they are immortal creatures who do not age. A Ghoul is functionally immortal and can continue to exist for eternity, provided there is a source of human corpses to feed from.
We allow Ghouls up to 6,000 years old on FMRP.
The older the Ghoul, the more physically powerful the Ghoul becomes. They can maintain their superhuman state for longer, fend off the decomposition for longer between feedings, and their regenerative abilities can become almost instantaneous. The body effectively becomes better and better at digesting the corpses and strengthening the Ghoul's magic.
However, the older the Ghoul, the more their mental stability can slip. Especially a Ghoul who has gone through repeated Zombie-like episodes. The human brain was not designed to die and revive and die over and over, nor was it meant to continue living after death. Ghouls often have to be wary about losing their sense of self and never regaining it back.
A Human can be turned into a Ghoul one of two ways: through their death and reanimation into a Ghoul, or from being infected by a Ghoul.
A Ghoul's magic, like all other magic, craves new blood, and Humans are a unique species void of all magic. If a Ghoul attacks a Human severely enough, the Ghoul's magic is transmitted from the Ghoul to the Human.
The wounds from the attack must be severe, life threatening, or fatal; unlike other species, something simple like a bite or a scratch is not enough to transmit. Typically a Ghoul only attacks with the intent to kill to feed.
If the Human manages to survive this attack, the Ghoul's magic begins to take over as an infection. What follows is extremely painful for the Human as the infecting magic begins to kill. The infection runs rampant through their body until it makes its way to the brain, where it takes permanent residence. This can take anywhere from a few hours up to a week.
The infection always ends in the Human's death, to rise again as a Ghoul. There is no way to stop it once it starts. The turning upon death is immediate; the Human may even be conscious to experience their own death. The newborn Ghoul often has an insatiable desire to feed and regain strength at this time.
If the Human does not survive the initial attack, if the Ghoul leaves the brain intact in the body during feedings, it is still possible for the magic to infect the brain and reanimate the corpse into another Ghoul within the two week reanimation window. As a result, brains are often a Ghoul's first target.
Ghouls can be created from other supernatural species as well - except for Vampires, Phoenixes, and Unicorns, whose bodies disintegrate after death and therefore can't be reanimated.
Once a Supernatural creature has died, their magic leaves the body, effectively turning the Supernatural into a Human corpse. That is what enables the Ghouls to do what every other species cannot: turn another Supernatural species.
The only way for a Supernatural to be turned is to die and be reanimated into a Ghoul. They can't be infected like Humans thanks to their innate magic.
However, if the attack is severe enough, and the Supernatural dies quickly enough afterwards, there are rare occasions where the Ghoul's magic can survive dormant for just long enough to infect the corpse once the Supernatural has passed and the magic has left the body.
Ghouls are incapable of producing children, whether with others of their own kind or another species. The only 'children' a Ghoul can make are the others they infect and turn into Ghouls.
It's not uncommon for lonely Ghouls craving that one lost aspect of existence to "adopt" families and name the mortals as their own. It's also not uncommon to steal children to raise as their own children.
A Ghoul can tell other supernaturals apart by smell. Each species, Humans included, have unique scent signatures that Ghouls can smell. Individuals also have unique scent signatures that a Ghoul can use to tell them apart from others.
Alternatively, other Supernaturals can only detect Ghouls by their scent as the undead creatures do not have a magical signature. To other Supernaturals, Ghouls will normally smell like graveyard soil and decay, though the severity of this depends on how recently they've fed.