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|Primary Power||Soul consumption|
|Notable Members||Sebastian Michaelis |
Claude Faustus (anime)
Hannah Annafellows (anime)
Ciel Phantomhive (anime)
Demon (悪魔; Akuma, also translatable as Devil) is a supernatural being who occasionally comes to the human world to form a Faustian contract with a human, offering a range of services in return for the future consumption of the individual's soul.
Demons consume on human souls, presumably for sustenance. They can do this by either forming Faustian contracts with humans or simply taking their souls forcefully. Human souls seem to differ in quality; Claude Faustus has once stated that a demon's - most likely those that nearly exclusively form contracts - life was to "cultivate a soul, and then feast on it", cultivate within the context taken to mean shaped.
There are two aesthetics of demons: one, their masters' orders are absolute and two, obey those orders while keeping their contracts. These two aesthetics are the reason for most demons' actions. There is no faith or loyalty that prompts them to act otherwise. However, demons are highly afraid of breaking their aesthetics, this being why they value their masters' lives above their own.
A contracted person receives a mark of their contract somewhere on his or her body, with a corresponding mark appearing simultaneously on the demon. The location of the mark can be chosen by the person who wishes to make a contract, or it can be the choice of the demon, as in Ciel's case. The more visible the location of the seal is, the stronger it is. Sebastian's contract symbol is on his left hand, and Ciel's symbol is on his right eye; in the anime, Claude Faustus' symbol is on his hand and Alois Trancy's mark is on his tongue. The contract mark is comparable to a scar or brand, and allows the demon to be able to locate his or her master at any time. It gives the human great authoritative power over the contracted demon, but at the same time makes it impossible for him or her to ever escape said demon. Sebastian likens the contract to a "collar." The placing of the seal is extremely painful. The mark Ciel and Sebastian share is in the form of a pentacle, i.e. a five-pointed star inside a circle, with the magic ward 'tetragrammaton' around it. In the anime, this would seem to be the standard design, as three different contract marks have been shown and all three were variations of a pentacle (in Hannah Annafellows' case, a pentagram). In marks placed by Sebastian and Claude the star design appears inverted, that is with two points upward rather than one, traditionally a sign of black magic or devil worship in Western occultism.
In order to create the contract, a human has to summon a demon. However, it seems that they do not need to be aware of the existence of demons, attempt to summon a specific demon, or even summon one intentionally, as Ciel states he summoned Sebastian accidentally. It seems that a human needs to have a lack of faith in God, and be desperately searching for a way out, if Ciel's situation is indicative of a typical summoning process, or at the least an "accidental" summoning process. Sebastian states that once summoned, this fact will not change for all eternity. All the same, it seems that the human still has the option to go through and create the contract, or dismiss the demon, as when Sebastian was summoned, he asked Ciel to make a decision. William T. Spears compares a demon's contract with humans to poking fun at them and then leeching anything that comes out as a means of survival, to which Sebastian replies he does not dismiss that claim. Demons seem to be independent operatives. They contract on their own behalf, and there is no suggestion that they serve any supreme power nor any evidence that such an entity exists in the series (though there is reference to God).
While demons are physically capable of consuming human food, as shown through Sebastian's sampling of lemonade, cake, curry, and wine at various points in the series, it seems that only human souls are able to satiate their hunger. William states that refraining from consuming souls can leave demons "starving" to the point that they cannot help themselves. This does not seem to negatively affect Sebastian, at least not in the same way starvation would kill a human, although Angela Blanc comments that his being starved causes him to feel more pain than normal when physically injured. All the same, demons do seem to be able to be afflicted by problems similar to humans, such as when Sebastian complains of heartburn after drinking lemonade that contained MSG instead of sugar.
Demons are said to be "devoid of love" and lacking in convictions and loyalties. Nonetheless, they have their principles, which include following their master's orders and maintaining the integrity of a contract.
Demons also seem to have a long-standing hatred of Grim Reapers, which is illustrated through Sebastian's interactions with William T. Spears and Grell Sutcliff, particularly in the manga. Grell sums this up by saying, "If the job of a Grim Reaper is to recover the souls of the dead, then demons can be likened to pests that snatch these souls away just for the sake of devouring them." Sebastian, on the other hand, calls their use of the Cinematic Record "just a terrible interest" and the worst sort of spying activity.
However, it is understood that, as far as demons go, Sebastian is not particularly harmful, as William states that he is "slightly better" than the others and that he's "not the type to feast."
Demons are shown to have a variety of abilities, including:
- Enhanced strength: Demons are shown to be vastly stronger than humans. Sebastian was able to cause an entire concrete dam to collapse after one punch, rip the top of a train car's roof, throwing it effortlessly and stopping a moving train with one hand.
- Enhanced speed: Sebastian has demonstrated the ability to outrun a car that was attempting to speed away from him. He is also able to block or dodge objects, such as his sword fight with Agni. He is also able to run to places in one hour that would take a day to get to by coach or railroad and outrun a moving train.
- Enhanced endurance: While fighting Grell Sutcliff, who was wielding his powerful Death Scythe, Sebastian was able to sustain multiple injuries from him and continue fighting while protecting Ciel. Sebastian is also able to survive attacks that would kill humans, such as when he was shot in the head and chest multiple times by Azzurro Vanel's men, get stabbed, slashed and even an arm severed yet continue on as if nothing had happened. However, more powerful weapons such as a Death Scythes can significantly weaken or even kill a demon.
- Enhanced senses: Sebastian is able to find humans based on smell, - including ones he has never personally met - is able to deduce if they are dead, alive, or injured and be able to discern if someone is a human or a member of another race, as shown when he quickly identified Agni as a human rather than a Grim Reaper, or even another demon. Sebastian states that he is able to pick up any kind of scent. He was easily able to hear the rifleman who attempted to kill him, his abilities extending to the point where he could see each and every person who escaped from Violet Dorm after it caught on fire. Demons also seem to be able to sense living souls.
- Transformation: Sebastian has demonstrated that he can switch between his human form to his true demon form and back quickly. In this form, he effortlessly killed a Fallen Angel within ten seconds - at least in the anime - and caused an explosion when Ciel's soul was missing, devastating an island. It is questionable as to whether this is an ability all demons have. Claude also seems to be able to transform into the form of a spider. During Episode 4, Claude is seen having a long, inhuman tongue briefly. And at other points of time, Claude has spun and shot webs while still in human form. Also, in the manga it is implied several times that Sebastian can change his appearance at will (though this is more along the lines of lengthening and shortening hair within the manga, but it's said that he can change his appearance to fit whatever's needed of him). He was also able to take away his skin conditions from the Werewolf's miasma by swiping his hand across a mirror.
- Soul staining: It is not known precisely how this works or what it entails, but Grell states that a demon's hands and lips have the ability to stain a soul. This, however, could simply by a metaphor, as Grell is known to speak in extremely unorthodox language patterns. 
- Fire control: By revealing the sign of his contract, Sebastian is able to set an entire mansion on fire from three small candles. It is unknown if this is an inherent ability or if a it is a demonic ability derived from the Faustian contract.
- Manipulation: Beyond making contracts for a human's soul, Sebastian has offered to make other deals or attempted to charm and manipulate people in order to get what he wants. William has called this the "signature" ability of a demon, and states that it works by "deceiving prey with sweet words and dragging them into darkness." While ineffective against William, he later uses this ability to get Beast, who initially dislikes Sebastian, to reveal important information.
- Body manipulation: Sebastian is shown to be able to twist someone's arm just by twirling his finger.
- Immortality: Sebastian has stated that a demon can live forever, and they will heal/regenerate from any injuries even if their entire bodies are destroyed, but a demon could get killed by a demonic sword known as Lævateinn (though this is exclusive to the anime), or a Grim Reaper's scythe .
- Manifestation: Sebastian was able to recreate the Phantomhive manor, including the building itself and all of the furniture and decorating, in a matter of three hours. He was also able to create a feast in an instant. Likewise Claude completely redecorates the Trancy manor in the time it takes a party of guests to arrive, and later changes the color of the interior walls overnight. Demons also seem to posses a great capacity for learning and retaining information, as shown with Sebastian quickly learning and excelling in cooking, art, language, music, etc.
- Demonic conversion: In the anime, demons are shown to be able to convert humans into demons. Alois Trancy (while possessing Ciel's body via his soul being placed in him) ordered Hannah to not allow Claude or Sebastian to obtain Ciel's soul. Ciel was then reborn as a demon, waking with the signature pink-slitted eyes and withstanding a direct attack from Sebastian. It is not clear if this ability is available to all demons.
- Levitation: It is shown that, when the first time Sebastian encountered Ciel, his feet weren't touching the ground.
- Claude Faustus (anime)
- Thompson (anime)
- Canterbury (anime)
- Timber (anime)
- Hannah Annafellows (anime)
- Ciel Phantomhive (anime only)
Known Contracted Humans:
- The word within Sebastian's contract sign, known as the tetragrammaton in English, is the Hebrew name of God. The most accepted pronunciation of the name is "Yahweh," but it is unknown what the proper pronunciation is. Most English translations of the Bible translate it as "LORD" 
- Sebastian has been seen wearing a rosary, which would suggest that sacred objects (such as crucifixes, holy water, etc.) do not have a negative effect on demons.
|Human · Demon · Grim Reaper · Bizarre Doll · Ghost · Doll · Fallen Angel|
|Sebastian Michaelis · Claude Faustus · Hannah Annafellows · Cantebury · Thompson · Timber|