Demons

Demons are malevolent spiritual entities created by Lucifer. Created from corrupted human souls after extensive torture in Hell, they're extremely evil. The first-ever demon was Lilith. The species as a whole function as the series' primary antagonists and are the most recurring creatures in the series.

Story
Demons were once humans, their souls having been corrupted and warped after spending hundreds of years in Hell being tortured and having all of their humanity burnt out of them. They are left as large, black clouds that generate electromagnetic interference and leave behind a sulfurous residue. The first demon was Lilith. She was created by Lucifer, who resented humans for taking his place as the most beloved of God. Lucifer wanted to show how bad humans were, so he tortured a human into becoming a demonic monster. He proceeded to do the same to any human souls he could trick into joining him. However, Lucifer was locked away by his own brother, the Archangel Michael, and Lilith was imprisoned deep within Hell. Thousands of years later, after much searching, Azazel, Lucifer's demonic "son", was able to find the doorway to Lucifer's prison. Lucifer revealed that only Lilith can break the 66 seals keeping him imprisoned, and instructed Azazel to find him "a very special child". Azazel spent the following years feeding his own blood to babies—one being Sam Winchester—as they would then grow up developing demonic abilities, including the ability to kill Lilith and hence free him from his prison, and then be powerful enough to serve as his earthly vessel.

Although an ordinary demon is featured as a villain of the week in the fourth episode of the series, Phantom Traveler, demons do not become actively involved in the show until the introduction of Azazel's "daughter"—possessing a girl named Meg Masters—in the second half of the season. She follows Sam and Dean Winchester, and later unsuccessfully sets a trap for them using their father.

Characteristics
Demons are the result of souls going to Hell, being tortured until no humanity is left in them, thus turning into demons.

There are many ways of becoming a demon, from making a deal with a Crossroads Demon, to being a witch, and making a deal with another demon. They usually appear in the form of a long, slender clouds of black smoke. Their true form has not been shown onscreen, however Dean has seen their true forms, before he was taken to Hell. He says they look horrible even go as far as calling Ruby "One ugly broad."

When they possess humans, they usually enter through their mouths, Although on one occasion are observed entering via the eyes (as seen in the episode "Phantom Traveler"). Often possessed humans physically look exactly the same as they did before possession, but the only noticeable changes are the mentality of the possessed human. Often under possession the human begins speaking and acting like the demon would. Upon exorcism the human retains no memory of their time during possession (Unless they have been "awake" during possession, in which case the time of possession is a nightmare for them). Upon possession, the only noticeable change of the possessed human is their eyes, which range from deep black to yellow, to pale white and to red, depending on the type of demon possessing them. The possessed humans also gain the powers of whichever demon is possessing them. Unlike angels, whose possession of a human vessel has to be with the vessel's consent, demons forcibly possess humans without any deal at all. Whenever they use their powers, they leave a trace of sulfur in the form of yellow dust. People suffering from stress, fear or panic can be vulnerable to demonic possession. Demons abhor the name of God (which in Latin is Dio or Deus).

Powers and Abilities
Demons don't get their powers from anything, unlike angels, who specifically rely on Heaven for most of their power.


 * Demonic Possession (displayed by all demons who gained human form) - They can possess people, and don't need permission to do so.
 * Immortality - (displayed by all demons) - Demons are basically unkillable, and only by supernatural methods may they die. Ruby's Knife can easily kill any (except Alastair, and likely Azazel) demon it hits, however it must be in a fatal position. They also fall by angelic power, although Alastair's highly immune to some of their methods, such as Killing Touch.
 * Teleportation (displayed by all demons) - Demons can teleport nearly anyplace on Earth, so long as it's not a Devil's Trap, barrier of Salt, or any other demon-warding place.
 * Super-strength (displayed by all demons) - They increase the strength of their host, the potential of which varies depending on the demon. They're stronger than most monsters. A group of demons combining their strength can apprehend a single, weakened Alpha
 * Telekinesis (displayed by all demons) - Demons can move objects and people withe their mind. The strongest of which can snap necks, break bodies, and pin people to walls.
 * Invulnerability (displayed by Azazel, Lilith, Alastair, and Samhain) - Demons can't die by guns, knives, bombs, or the like, however they possess some weaknesses, however some demons are even immune to those. Alastair is one of the most immune demons ever shown (however he could still be hurt with Holy Water).
 * Resurrection (displayed by Azazel, Crowley and Crossroad demons) - No demon can resurrect out of the context of a deal. Demons require deals to revive the deceased, unlike angels. The demon who's the King of Hell can resurrect on a whim.
 * Telepathy (displayed by all demons) - A very common demon power, demons can read the minds of humans.
 * Supernatural Perception/Senses - (displayed by all demons) - Demons can see numerous beings that are invisible, like angels, and reapers.
 * Super Stamina - (Displayed by all demons) - Demons never tire. However, there are some methods of slowing them down.
 * Pyrokinesis (displayed by Azazel, Crowley and Brady) - A rare ability, that normally only the very powerful posses, some demons can manipulate or generate fire by mind.
 * Demonic White Light (displayed by Lilith and Samhain) - This ability is seemingly inherent in all white-eyed demons. Emanated from the palm, it's emitted in a burning sensation, capable of causing great devastation.
 * Reality Warping (Displayed by Azazel, Lilth and Crossroads demons) - In the context of a deal, some demons can alter reality, grant talent, cure the sick, make others fall in love etc. Azazel posses the most advanced form of this as he doesn't require a soul as payment, he can simply do it by will.

Weaknesses

 * Salt - Demons are unable to cross a line of salt and can do very little to damage the line at all. They can't even open doors lined with salt if opening it would break the line. Salt can also be used to torture demons by making them ingest it or by injecting them with salt-water. It can also be put into shotgun rounds to hurt and knock back demons. Azazel is immune to this weakness.
 * Holy Water - Holy Water burns demons that come into contact with it, like acid. It proved ineffective against high-tier demons like Azazel or Lilith, and Ruby practically laughed when Sam was about use it against Alastair because it would barely slow him down.
 * Iron - A demon can't touch iron without its skin burning or cross it if it's used to erect a barrier, much like salt. Samhain is immune to this weakness.
 * Ruby's Knife - The knife originally belonged to Ruby. It will kill a demon that is within a host if the wound dealt is a fatal one. Upper level demons are immune to the killing effects of the knife, the only definitive example being Alastair.
 * The Colt - Much like Ruby's Knife, it will kill any demon that is shot while within a host if the shot is a fatal one. It's more powerful, however, as it affects upper level demons as well, even when the knife does not.
 * Bones - If the bones belonging to the demon are burned, the demon will be killed much like a vengeful spirit. This can also be used to torture demons. This until recently was believed to be merely a rumor, however Bobby tested this method against a Demon resulting in her death. Crowley may have been aware of this method as he tried to convince Bobby it was "A myth". This tack is very difficult to use because it requires knowing the demon's human name from before it died and where they were buried, and many demons themselves can no longer remember they were ever human at all, let alone what their names were. Devils_Trap_by_Pandora_Gold.jpg
 * Exorcism - Will pull the demon out of its host and send them to hell. Hosts may not survive.
 * Devil Trap - A Devil's Trap will hold a demon in place and prevent its escape. The Trap will also prevent low-level demons from using their powers, though Castiel's Enochian circle was able to completely bind even Alastair's abilities. It also locks a demon inside its host unless it is exorcized. For some reason, a demon inside a trap is usually unable to do anything to damage the integrity of the circle, which would allow its escape. Azazel is immune to this weakness.
 * Angel's Touch - An angel can kill a demon by touching them on the forehead with their hand. This power will not work if the demon is too powerful or if the angel is cut off from Heaven. The host is also killed as a result.
 * Special Children - Sam Winchester developed special abilities almost especially tailored to hurt or kill demons. Due to training from Ruby and ingestion of demon blood, he first developed the power to pull demons out of humans. Later the powers advanced to killing demons outright, much like the knife or the colt. Although unknown, it is assumed the other special children would have also been able to do this as well, had they survived, trained, and ingested demon blood.
 * Palo Santo - Basically a wooden, hybridized version of salt and holy water. When a demon is stabbed with it, it causes the wound to smoke and painfully pins the demon to a single spot, immobilizing them long enough to perform an exorcism. Palo Santo isn't commonly used by many hunters due to the fact that it damages the hosts the demons are possessing.
 * Flesh Sigil - By carving a particular sigil into a demon's possessed flesh, it's possible to lock the demon within its host and disable its powers, the most important one being teleportation. However, demons with these sigils are not bound to a single place and can roam around freely if not restrained by some other means.
 * Hallowed Ground - Some demons (lower-level ones) are unable to enter hallowed ground. It's unclear if this includes cemeteries as well as churches.
 * "Christo" - In Phantom Traveler, Sam explained that simply saying Jesus's name—Christo (pronounced "KREE-stow")—would cause a demon to flinch, turning its eyes black and revealing its nature. This particular aspect of demon lore was dropped for the rest of the series with the intent of making it more difficult to discover if a character was possessed, thus upping the surprises and scares.

Yellow-Eyed Demon
Azazel is the only yellow-eyed demon in existence (thus far) and is incredibly powerful. Besides having a unique durability threshold, advanced telekinesis, he can manipulate fire, control dreams, make electrical devices go haywire, and can even possess Reapers. The leader of the demon army, Azazel is subordinate only to Lucifer. He is impervious to Holy Water and other conventional defenses against demons.

White-Eyed Demons
The most powerful class of demons, white-eyed demons possess numerous powers, the most deadly of which being white light emanation. They are highly dangerous and they rank very highly in the hierarchy of Hell, just under Lucifer. The only known demons of this type are Lilith and Alastair.

Special
Throughout the course of Supernatural, the Winchester brothers have battled demons that are unique in some way. Examples of these demons include:


 * Monocoloured-Eyed Demons, such as Samhain, the origin of Halloween who is summoned through three blood sacrifices;
 * The Seven Deadly Sins, the physical embodiments of the Seven Cardinal Vices;
 * The demons that cause natural disaster as on the episode Phantom Traveler - Season 1 (causing airplane crashes)
 * And the Acheri, demons from Indian mythology that can spread disease, appearing as young girls with felinistic features

Elite Demons
Only appearing at Lucifer's side in "Swan Song", these two demons were extremely strong.

Crossroad Demons
Crossroad Demons have red eyes and are shown bargaining with desperate people. 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...

Black-Eyed Demons
The most common demons on the show, black-eyed demons possess little to no power, whether it be super-strength or telekinesis. Effective defenses against these demons include holy water, salt, iron, a devil's trap, etc. Stronger black-eyed demons, such as Meg Masters, are not barred in entering hallowed ground and one demon, Tammi, 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.

Apocalyptic Tools
During the course of the fifth season, though not really demons, numerous tools/instruments in service of Lucifer have been introduced:

Three of Lucifer's most highly-used instruments were Pestilence, War and Famine. Jesse Turner was intended to serve Lucifer, but chose not to, and the Whore of Babylon rose sometime after Lucifer did, damning all she could to Hell. Death, the oldest and most powerful Horseman, also served Lucifer, but did so unwillingly and resented being bound to a "bratty child throwing a temper tantrum." Death eventually met with Dean Winchester and gave him his ring which the Winchesters needed to re-imprison Lucifer.

Appearances
They have appeared in 59 episodes to date.

Season 1

 * "Pilot" (as a silhouette (later revealed to be Azazel),)


 * "Phantom Traveler" (Introduced).


 * "Scarecrow"


 * "Shadow"


 * "Salvation"


 * "Devil's Trap"

Season 2

 * "In My Time of Dying"


 * "Croatoan"


 * "Born Under A Bad Sign"


 * "All Hell Breaks Loose - Part 1"


 * "All Hell Breaks Loose - Part 2",

Season 3

 * "The Magnificent Seven"
 * "The Kids Are Alright"


 * "Sin City"


 * "Malleus Maleficarum"


 * "Dream A Little Dream Of Me" (in one of Dean's dreams)


 * "Jus In Bello"


 * "Time Is On My Side"
 * "No Rest For The Wicked"

Season 4

 * "Lazarus Rising"


 * "Are You There, God? It's Me, Dean Winchester"


 * "In The Beginning"


 * "Metamorphosis"


 * "Yellow Fever" (as Dean's hallucination)
 * "It's the Great Pumpkin, Sam Winchester"


 * "I Know What You Did Last Summer"


 * "Heaven and Hell"


 * "Criss Angel Is A Douchebag"


 * "Sex and Violence" (Ruby's Voice)


 * "Death Takes A Holiday"


 * "On The Head Of A Pin"


 * "The Rapture"


 * "When the Levee Breaks"


 * "Lucifer Rising"

Season 5

 * "Sympathy for the Devil"


 * "Good God, Y'all" (as hallucinations created by War)


 * "Free To Be You and Me"


 * "I Believe The Children Are Our Future"


 * "Abandon All Hope..."


 * "Swap Meat"


 * "My Bloody Valentine"


 * "99 Problems"


 * "The Devil You Know"


 * "Two Minutes to Midnight"


 * "Swan Song"

Season 6

 * "Exile On Main Street" (as an hallucination created by the Djinn poison)


 * "Weekend At Bobby's"


 * "Family Matters"


 * "All Dogs Go To Heaven"


 * "Caged Heat"


 * "Mommy Dearest"


 * "The Man Who Would Be King"


 * "Let It Bleed"


 * "The Man Who Knew Too Much"

Season 7

 * "Meet The New Boss"
 * "Slash Fiction"
 * "Season Seven, Time For A Wedding".
 * "Repo Man"
 * "The Born-Again Identity"
 * "Reading Is Fundamental"