Demons in the Supernatural universe are malevolent spirits originally created by Lucifer. They are usually created from corrupted human souls after extensive torture in Hell (or, in Lilith's case, by Lucifer himself), but alternatively, a human can be transformed into a demon by the Mark of Cain's effects; if the one who owns the First Blade and possess the Mark of Cain is killed, the Blade will resurrect him as a demon (probably a Knight of Hell).
The species as a whole functions as the series' primary antagonists, and are the most recurring creatures in the series. Similar to angels, they require a vessel to walk the earth, though they are able to roam in their smoke form.
The true form of a demon when not possessing a human is almost never seen. In "All Hell Breaks Loose, Part 2," however, after John Winchester's ghost pulls Azazel out of his vessel, a decaying skull-like face is visible within Azazel's smoke form. This is arguably also seen in demons stabbed with the demon knife or an angel blade, when their vessels flash orange and the skeleton beneath is visible. From this statement, it can be assumed that a demon's true form is, in fact, a skeleton engulfed by smoke.
The most common and standard class of demons on the show, black-eyed demons possess only basic powers, such as super-strength and telekinesis. Effective defenses against these demons include holy water, salt, iron, a devil's trap, etc.
Stronger black-eyed demons, such as Meg, are not barred from entering hallowed ground and one demon, Astaroth, is shown to have the ability of causing internal bleeding and extensive magical knowledge, such as when she recites a ritual to exorcise Ruby from her body. Astaroth was also able to stop a bullet shot from the Colt in mid-air.
Although the Knights of Hell are black-eyed demons, they are far more powerful and possess much greater abilities.
Crossroad Demons have red eyes. Unlike normal demons that serve the King of Hell, Crossroad Demons tend to be more self-serving, often bargaining with desperate people, making deals in exchange for their souls after a certain amount of time (usually ten years). They can grant wishes, collect souls, teleport, and be summoned by digging a hole in the center of a crossroads and burying a box with a picture of the summoner, some graveyard dirt, and a bone from a black cat. Gifted with immense power, these demons usually possess attractive women to lure men into making deals, although there are exceptions.
White-eyed demons are considered the generals of the demon race. They're terrifyingly powerful, and they rank the highest in the hierarchy of Hell, just under Lucifer himself. They inspired fear in their subordinates, as all other demons seemed to be terrified of them.
Being as powerful as they are, white-eyed demons are resistant to many demonic weaknesses; they are even capable of holding their own against regular angels. So far, the only known demons of this type are Lilith and Alastair, the former of which was the very first demon to be created.
Azazel is the only yellow-eyed demon to appear in any episode thus far. Besides having a unique durability threshold and advanced telekinesis, he could manipulate fire, control dreams, make electrical devices go haywire, and could even possess Reapers. The initial leader of the demon army, Azazel was the mastermind of the master plan to free Lucifer from Hell. He was impervious to holy water and most other conventional defenses against demons.
Knights of Hell
Knights of Hell are very powerful demons that were handpicked by Lucifer himself and created/trained by Cain, the Father of Murder. They are some of the first fallen demons. A legend among the Men of Letters had it that Archangels destroyed all the Knights of Hell, except one (Abaddon), but in truth, Cain himself killed them.
Knights of Hell possess a number of abilities not seen from other types of demons. They are also nearly invulnerable, being immune to exorcism rites and even the demon-killing knife. The only weapon that can kill a Knight of Hell is the First Blade. With Abaddon's death, and when Dean kills Cain in Season 10, the Knights of Hell are extinct.
Cambions, also known as "Katako" or "Antichrists," are immensely powerful half-breeds that are half-demon and half-human. They are capable of altering reality involuntarily based on their thoughts and beliefs, teleporting with a thought, causing destructive tremors when feeling very angry, and binding or even expelling demons with a verbal command. Their power grows when Lucifer is free from his cage.
Very little is known about how a Cambion is created, except that they are conceived and born of a virgin woman who is under demonic possession from the start to the end of the pregnancy.
Jesse Turner is the only known Cambion.
Whore of Babylon
The Whore of Babylon is a special demon seen in the Season 5 episode "99 Problems," where she possesses Leah Gideon, the daughter of a priest who doesn't even know the girl he knew is dead. Sam and Dean Winchester work out that the Whore, an ancient demon and apostle of Lucifer, is possessing her, and tell her distraught father, but the father vows to kill the demon that killed his daughter because he is a man of God and he can kill demons.
The Whore of Babylon's mission is to bring down entire townships, and deceive and corrupt innocent human souls so they will go to Hell and increase the demon army. She was killed by Dean.
Hellhounds are unique demonic entities which appear as large dogs of blackness with super-speed as their main power. They also specialize in dragging their victims into Hell itself, and thus turning Crossroad Demons' clients into demons. Hellhounds have owners; Crowley had one, as did Lilith. Certain Hellhounds are larger than normal; Crowley's Hellhound was almost twice his size.
Before the show
Lucifer created demons with the intent of spiting God for preferring humans to him, and/or proving how flawed and abominable humans were. He had demons on Earth to seduce and trick humans into following him and ending up in Hell. The very first demon was Lilith, and the other first-born demons included Abbadon, Cain, Azazel, Samhain and the other Knights of Hell. The demons grew and became more powerful, but they needed a human host to act on Earth so not to arouse suspicion.
In the 1860s, Cain met a human woman named Colette Mullen, and fell in love with her, restoring his humanity. Worried that the Knights of Hell took her, Cain killed them all except Abaddon, who possessed Colette and managed to trick Cain into killing Colette; however, with her dying breath, Colette made Cain promise never to kill again. As such, Abaddon and Cain became the last Knights of Hell.
In the 1950s, Father Max Thompson invented a ritual where an imprisoned demon was injected with human blood and slowly became human again; this allowed Sam and Dean to perform this ritual on Crowley in 2013 as part of the Trials to permanently close Hell.
In the show
In "Phantom Traveler," a demon was bringing down planes within forty minutes of the flight, killing almost all on board, so Sam and Dean had to stop him. They went on the plane, and Dean conquered his fear of flying to bring down the demon. They were successful but could not kill the demon; they only sent him back to Hell. This was the first demon they met in the show itself.
Later, in "Scarecrow," Sam met a girl named Meg, who was revealed to be a demon when she was unleashing spirits called Daevas onto Chicago in the episode "Shadow." Sam was tortured by Meg, but he and Dean fought back and overpowered her. Meg said she was Azazel's "daughter" and was working with him.
Sam and Dean realized Azazel was forming an army using human children (including Sam himself) with supernatural abilities; in Sam's case, it was precognition and telekinesis. In "Salvation," they saved a woman from being killed by Azazel in the same way Azazel had killed Sam's girlfriend Jess and the brothers' mother Mary, stopping the woman's daughter from becoming one of Azazel's "special children."
When Sam was kidnapped by demons and taken to a town called Cold Oak, Dean got there and saw Jake Talley and Sam fighting, but Jake killed Sam and ran off. He met Azazel, who said Jake needed to open up Hell. Meanwhile, Dean met with a Crossroads Demon, with whom he made a deal to sell his soul in exchange for Sam's resurrection. The demon revived Sam, but said Dean's price was for him to go to Hell in a year and in doing so become a demon himself after forty years' torture. Dean wanted his brother back so he agreed but too late realized his future was taken from him.
When Jake opened Hell and unleashed hundreds of demons on Earth, Dean killed him and also Azazel. He freed John from Hell, and then Dean and Sam set out on hunting down the demons that had escaped Hell.
They met the Seven Deadly Sins, seven evil demons which had been imprisoned deep in Hell, but they killed/exorcised all of them. The demons grew more invincible, and in one town they met a demon named Casey who said that they had no leader any more but were seeking Sam as theirs.
Sam noticed he was being followed by a woman named Ruby, who revealed herself to be a demon. She met Dean and while he disliked her, he knew she could be valuable to inside information about demons and their plans.
After Sam and Dean were arrested by FBI, hundreds of demons performed a mass possession and converged on the police station, hoping to kill everybody and Sam and Dean. Ruby appeared and she said there was a new leader of Hell now, named Lilith, who was the first demon and most powerful. Now Lilith was going to take Dean to Hell and kill Sam. The siege broke as demons attacked. All were exorcised with Holy Water and salt and things got back to normal. But Lilith arrived in the station with a demon and killed everybody inside, blowing up the center.
Lilith hunted down Dean and Sam and when their time was over, she appeared to Dean and called her Hellhounds, dragging him into Hell.
Before the Apocalypse
Dean was in Hell now and Alastair, the chief demon torturer, chopped him up for forty years and asked him each day if he wanted to become a torturer, Dean refused. Eventually angels broke into Hell and Castiel rescued Dean from Hell. He resurrected him and they met the angels, who said the 66 Seals which were containing Lucifer were breaking and soon the Devil would be free. So they were stopping the locks from breaking.
Eventually they failed and Lucifer freed himself. Ruby said she was on his side all along and wasn't with the brothers, so they killed her as a traitor. Now Lucifer was free and demons approached him. During the ritual to free Death, many demons sacrificed themselves for him. Lucifer said to a shocked Sam "So what? They're demons."
During the Apocalypse
Now that Death was out, the other Horsemen began returning and announced themselves, bringing on the Apocalypse. Demons protected the Horsemen, especially Famine, who was in a wheelchair; these demons, however, were eaten by Famine.
When Lucifer was defeated, demons were again in chaos. Soon, Crowley came out of the shadows and made himself King of Hell, calling demons to him.
Under Crowley's rule, Hell was made into a never-ending queue. The demons were encouraged to openly possess people on Earth and fight Sam and Dean. When the Leviathans appeared, Crowley called off the demons from attacking because he hated the Leviathans and wanted them dead. But once their leader was dead, he allowed demons to attack Sam and Dean again. Sam and Dean then plotted to close the gates of Hell but couldn't do it as Sam would die from it. The demons eventually fell into a civil war started by Abaddon, who planned to overthrow Crowley and take over Hell and even Earth itself. A lot of demons even sided with the Knight of Hell and Dean visited Cain in order to retrieve the First Blade, as it was the only weapon that could kill her. Unfortunately the blade wasn't there and Cain gave him the Mark of Cain so he could use the ancient weapon in order to defeat her. She was eventually defeated by Crowley with the help of Dean and Sam. After Dean was killed by Metatron, he became a demon due to the mark. After wrecking havoc as a demon, he was tracked down by Sam and cured. During this time, Crowley restored order to Hell. Cain started going on a killing spree due to the mark and reluctantly had to be killed by Dean. After the witch and Crowley's mother, Rowena betrayed him, Demons were ordered to hunt her down. Rowena later removed the Mark of Cain from Dean's, a ancient primordial entity known as the Darkness was released from her imprisonment in the mark. The Darkness became a female human baby named Amara. She quickly grew into a little girl and was taken in by Crowley so he could watch and keep control of her. During this time, she fed on human souls and many demons were eaten by her. She grew into her teens and eventually betrayed Crowley. This caused Crowley and the Winchesters, with the help of Rowena, to go to Lucifer's cage and ask the evil archangel for help on how to stop her. Lucifer took advantage of the situation and escaped the cage with help from Rowena and by possessing Castiel. Lucifer quickly overthrew Crowley and the demons were once again serving him. The demons then spent their time helping Lucifer find the hands of God and weapons from the archangel's crypt in order to defeat Amara. Later, Crowley is back on the throne and asks the demons to join him defeat Amara to make Hell great again. But they laugh at him, saying he has made hollow promess so far. However, a big number of demons in their smoke form, soon joined by Crowley, also in his smoke form, make a collective attack on Amara to weaken her for God and Lucifer to finish her off. They succeed but the final stage of the plan fails, and Amara defeats God. The demons presumably returned to Hell in the aftermath. They are also said to have raided Crowley's stash of souls.
Powers and Abilities
- Immortality: A basic power shared by all demons, whatever their rank. Demons doesn't age and are unaffected by disease and toxins. They can't be killed by firearms, bullets, knives, blades and any conventionnal weapon. However they can be killed by supernatural means (higher demons, angels, and magical weapons).
- Teleportation: Demons can instantly teleport themselves anywhere.
- Telekinesis: Demons can move objects and people with their mind, they often uses this ability in order to push away enemies. Higher demons can even kill people by snapping their necks or pin them to a wall.
- Superhuman strength: Demons possess a superior physical strength and can easily overpower humans and even some monsters. Higher demons can even overpower low-level angels.
- Superhuman senses: Demons are able to see supernaturals beings who are normally invisible to humans and some monsters, like ghosts, reapers and hellhounds.
- Possession: Demons requires a vessel (a human) to travel on Earth. However they don't need the person's consent unlike angels. When they possess a human, they have access to the memories and the knowledge of their vessel. However, unlike angels, they don't heal their vessels when they're injured and if the vessel has took too much damage (a high fall, many shots or stabbed in the heart), the human is going to die when the demon will leave the body.
- Biokinesis: Mid-level and higher demons can manipulate the biology of humans beings. Azazel could torture people by causing hemorrhage and Abaddon caused people to bleed from their eyes and Crowley was able to create a massive pain in Sam's hand.
- Dream Walking: Azazel was able to speak to Sam in his dreams.
- White Light: Higher level demons like Lilith and Samhain were able to generate a powerful white light from their hands, able to obliterate people and large areas.
Demons can be trapped by a Devil's Trap, they are unable to get out of the circle, to use their powers or to damage the circle. Salt and Holy Water can also be used to harm demons, but this only works on low-level demons.
Demons can be killed by higher demons and also by some other monsters and creatures like archangels, angels and leviathans. Though conventionnal weapons are uneffective against demons, supernatural weapons can kill or at least harm demons like an angel blade, the First Blade, Ruby's knife or The Colt. Powerful witches can also kill low-level demons.