All Demons live in Gehenna. There are many different kinds of Demons. The Demons can pass over into the world of Assiah by possessing anything that exists, both living and non-living.
Demons' greatest weaknesses are their tail and heart. The heart of Demons serves as their source of power and one Demon can draw its full potential once their heart is out. However, once destroyed, the Demon would die which makes them at their most vulnerable.
Satan
- Main article: Satan
Baal (Eight Demon Kings)
Samael
- Main article: Mephisto Pheles
The King of Time.
Astaroth
- Main article: Astaroth
The King of Rot.
Amaimon
- Main article: Amaimon
The King of Earth.
Lucifer
- Main article: Lucifer
The King of Light.
Egyn
The King of Water.
Azazel
The King of Spirits.
Beelzebub
King of Insects.
Iblis
The King of Fire.
Kin of Astaroth
Demons that are associated with Astaroth, the King of Rot.
Coal Tar
Coal Tar (魍魎, kōrutāru, literally meaning "all kinds of spirits and goblins") are tiny, airborne Demons that possess fungi, flecks of dust, and dirt. Though they are at the bottom of the Demon food chain, they also far outnumber any other species, and become a threat once they band together. They are attracted to dark, dank places, as well as humans with dark natures. Breathing them in can cause one's lungs to rot. They usually swarm around other Demons.
There are two types of Coal Tar. One kind is fairly harmless, only floating around in the air. This type had oval-shaped green eyes and slightly open, downward curved mouths. The other type appears to be more sinister. These have slanted violet eyes and evil smiles.
Naberius
Also called a corpse guard dog, Naberius is a Mid Level Demon which is made by cobbling together multiple Ghouls for use in fighting against Demons. Currently, there are many cases in which they can no longer be kept tame and go wild. For that reason, as well as ethical concerns, Naberius Demons have been forbidden and the technique is sealed away. However, Igor Neuhaus still keeps Naberius Demons as his familiars. Their spirit wound can be fatal and can burn a victim, causing them to suffer from necrosis.
Ghoul
Ghouls are Low Level Demons that possess human and animal corpses. They mainly appear in countries where it is customary to bury the deceased, and methods of driving them away vary according to the country's customs and beliefs. Cremation is the most common method in Japan, so most of the ghouls there are animal ghouls. Ghouls have ravenous hunger for dead human flesh.
Impure King
- Main article: Impure King
Impure Princess
Another Demon who belongs to the Impure family (Impure King, Princess, etc.). Like the Impure King, the Impure Princess releases dangerous and noxious miasma, but weaker than his.
Kin of Amaimon
Demons that are associated with Amaimon, the King of Earth.
Goblin
Demons that possess small animals like mice and moles. As their Demonic powers are weak, Goblins are only capable of causing mischief, but on rare occasions, a large-scale Goblin with devastating powers emerges from their midst. They usually live in colonies controlled by a king or queen. There are several kinds of Goblins, and the hobgoblin is one of them.
Golem
Greenman
- Main article: Greenman Spirit
Greenmen are Low to Mid Level Demons that possess mud dolls called golems and then sprouted moss and other plants. They have the power to produce plants from their body in any season. They are peaceful in nature and enjoy basking in the sun. An infant Greenman named Nii-chan has become Shiemi Moriyama's familiar.
Snowman
Similar to Greenmen, Snowmen are Demons that also possess clay golems, but with a coating of snow.
Sea Monkey
Sea Monkeys are Demons that have the ability to control the growth of reef organisms.
Dökkálfr
Demons that possess plants and trees. While they normally only like conversations and play tricks, these Demons can grow violent if their possession is threatened. They can take control of its host when desired.
Bariyon
Also known as Saezuri-ishi, Bariyons are Low Level Demons that possess rocks and similar items. Most of the time, they are motionless and make nonsensical sounds. They are harmless, but the longer you hold them, the heavier they become. Older and stronger ones may jump on your back and weigh you down.
Naga
Naga are Low to Mid Level Demons who possess serpents. Various species exist around the world. Many who are evil, but in Japan, many are revered as gods for the benefit they bring. Their leaders can live for a long time and are called Nagarajas. A Naga familiar belongs to Mamushi Hojo.
Kin of Egyn
Demons that are associated with Egyn, the King of Water.
Leaper
Leapers are Low Level Demons that possess frogs. They exist all over the world in various sizes, but they are carnivorous. In Europe, some grow wings, skip across the water, or generate ultrasonic waves. Also, Leapers can look into the eyes of the people around them and read their emotions. If they pick up any fear, sadness, anger, apprehension, or any kind of agitation, they will attack. However, if a person remains calm, they will not attack.
Kraken
A Kraken is a Demon in the form of a giant squid. It has the ability to create swirls in the water, summon small squids, and to multiply itself if it is too weak or dying.
Naiads
Demons that purely consist of water, taking the form of women with a long dress. Yukio has been shown to be able to summon 7 of them. They are capable of summoning a Water Dungeon, surrounding, imprisoning, and potentially drowning the enemy. Their true power hasn't been fully shown, because Yukio was too inexperienced to summon them at full power.
Wadatsumi
A Wadatsumi is a giant water Demon in the form of a great whale. The Demon communicates with his mind.
Amatsumihiko was revered as a god by locals on the Atami beach 1500 years ago, and has become weak with neglect and hunger. The Kraken fears his power and avoids the beach because of him. He is easily impressed by the offerings from humans.
Kin of Azazel
Demons that are associated with Azazel, the King of Spirits.
Ghost
Ghosts are Low Level spirits who recently died and possesses its former body, materializing it into mist and vapor. They cannot cross into the afterlife until their last wishes are fulfilled and imposingly haunt areas, scaring people. Ghosts also retain memories and personalities from their past lives. Ghosts can be solid enough to sit on a solid object or touch someone, but can also float through walls and other solid objects. The manner of exorcism depends on the deceased's practices and beliefs in life.
Mayuko
Mayuko is one of the seven mysteries of True Cross Academy. She is the embodiment of the ugly thoughts of women and appears in a restroom of the women's dormitory.
Kin of Beelzebub
Demons that are associated with Beelzebub, the King of Insects.
Chuchi
Chuchi are Low Level Demons that possess small insects. They are known to swarm around animals and suck their blood, as well as feed on corpses. Though this is rare, some Chuchi reach gigantic proportions.
Kin of Iblis
Demons that are associated with Iblis, the King of Fire.
Peg Lantern
Peg Lanterns are Low to Mid Level Demons that possess man-made lighting equipments. Various types exist around the world. Once lighten, they consume anything within their range and are particularly fond of women. Their movement stops once they've run out of fuel or when they are sealed.
Salamander
Demons that possess lizards. Salamanders have streamlined physiques, stubby arms, a row of spikes on their backs, long hind-legs for sprinting, and their horned heads are similar to that of traditional European dragons. They have flames radiating from their bodies and are capable of breathing fire.
Kin of Samael
Demons that are associated with Samael, the King of Time.
Phantom Train
Phantom Trains, which are also called "man-eating" trains, are Mid Level Demons that possess trains. They "eat" their passengers by trapping them inside, which in turn, starves them to death and turns them into ghosts. They have the ability to travel between Gehenna and Assiah.
Kin of Lucifer
Demons that are associated with Lucifer, the King of Light.
Seraphim
Seraphim are Demons seemingly made of a blinding light. They are able to transmit the voices of the Illuminati and even to explode to damage the target.
Others
Gehenna Gate
It can be opened by using Satan's blood. It doesn't let go of anything that enters it, and it closed when Rin stabbed the heart on its top.
Byakko
- Main article: Byakko
Byakko are Low to High Level Demons that possess foxes. Byakko serve shrine maidens and are shown to be disobedient to those who lack self-confidence. As Demons that possess animals and serve as messengers to gods (神使, Shinshi), they coexist with humans. Byakko were originally popular in Japan as guardian deities of foods and agriculture. The older ones are intelligent and can understand human language. They will enter into agreements with people and as long as the agreement is kept, they bring benefit, but otherwise, they may inflict harm. Two Byakko are the familiars of Izumo Kamiki.
Cat Sith (Sídhe)
- Main article: Kuro
Low to High level Demons that possess cats. If a Japanese one lives long enough, its tail splits in two, thereby leaving it with two separate tails that easily distinguish it from normal felines. They also have two small horns on top of their heads. Cat Siths were shown to be deities centuries ago and can become violent by growing large and attaining Demonic features. They're different from Shinshi, but the older ones are smart and may enter into agreements with people to live with them. For hundreds of years, they may move from house to house, posing as normal pets. One Cat Sith is Kuro, who becomes Rin Okumura's familiar.
Shapeshifter
Shapeshifter as the name suggests can alter its appearance. It generally appears to a person as something they greatly fear. A shapeshifter was one of the Seven Mysteries of True Cross Academy.
Anime Exclusive Demons
Fungus Demon
Kin of Astaroth, King of Rot. It multiplies by spreading spores, which grows to mammoth proportions.
Malkin
- Main article: Malkin
Known as the "Bountiful Guardian Spirit", Malkin are Demons that possess scarecrows. It uses a spade and fangs to fight. Nagatomo has a Malkin as his familiar.
Ukobach
- Main article: Ukobach
A stove spirit rumored to sneak into kitchens and make delicious meals while people are sleeping and improves the flavor of the food in the area. It tends to misbehave and become wild if anyone trespasses in its territory or dislikes its cooked meals. It was once a familiar of Mephisto, who put him in charge of cooking Rin and Yukio's meals at their dorm.
Mara
Demons that possess Buddhist/Kannon statues in temples and attacks random humans. They supposedly tempted Buddha when he was about to reach enlightenment, taking advantage of the weaknesses and uncertainties of the human soul.
Gale
- Main article: Gale
An intermediate Demon in the form of a bird, who can possess people by using his or her own fear or the dark side of their souls. He possessed Konekomaru Miwa, after which he was killed by Rin.
Yamakujira
A Demon in the form of a gigantic boar. It is also a ruler of a forest like the Chuchi.