Demons/Synopsis

Early History
"Demon Sunday school story? God prefers humans to angels. Lucifer gets jealous. And then he gets creative, and he tempts and twists a human soul into the very first demon."

- Ruby After humans were fully evolved, God created a paradise on Earth called the Garden of Eden. He placed humanity in the Garden, and declared them his favorite creations. He told all the angels in Heaven to bow down before the humans, to serve them and love them more than him. The archangel Lucifer refused to bow down before a species that was younger, and inferior to him. He claimed that they were "flawed, and murderous." He declared war against God, and was eventually cast down to Earth.

God placed his most trusted angel, Gadreel, to guard Eden from the The Devil. He failed as Lucifer tricked him and snuck into the garden. To get vengeance on God, he tempted Lilith and corrupted her soul, making her into the first demon. Lucifer, still in the garden, further spited God by tricking Adam and Eve into eating the forbidden fruit. God cast humanity out of the Garden for disobeying him.

Following the creation of Lilith, Lucifer personally created and empowered four demons named Azazel, Ramiel, Dagon and Asmodeus. These four would become known as the Princes of Hell and were Lucifer's heirs and generals of demonic armies.

Years later, Adam and Eve had two sons, named Cain and Abel. Satan manipulated Abel into worshiping to him rather than God. Cain saw what Lucifer was doing, and offered his own soul, so that Abel's could go to Heaven. Lucifer agreed to the deal, but Cain had to be the one to kill Abel and take upon the Mark of Cain, the first curse in existence created by God himself. Cain obeyed, and bared The Mark. At some point he died, but The Mark didn't let him go, and instead transformed Cain into a powerful kind of demon called a Knight of Hell. On Lucifer's orders, Cain trained more demons, eventually creating a demonic army known as the Knights of Hell. Among these chosen demons was Abaddon.

Seeing the threat the fallen archangel posed to creation, God created a personal cage for Lucifer, which was locked by bound with 600 powerful seals and needed 66 broken to open. The demon Samhain was chosen to be a seal along with Lilith, whose death would be the final seal to set The Devil free. As time went on, the demons that knew of Lucifer's existence gave up search and the younger demons disbelieved his existence, except for Azazel.

History
"It might take centuries, but sooner or later hell will burn away your humanity. Every hell-bound soul, every one turns into something else. Turns you into us."

- Ruby to Dean 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. Following the release of hundreds of demons from the Devil's Gate at the end of Season 2, demons become the greatest, most common enemies the Winchester Brothers face in the series. At the same time, Dean Winchester kills Azazel with the Colt, creating a power vacuum.

Due to Azazel's death, the demons are initially disorganized and unable to execute their master plan. Some demons want Sam to lead them, while others follow Lilith. By the beginning of Season 4, however, Lilith has taken control of most of the demons and directs them to break the 66 Seals needed to free Lucifer. Under her direction, the Seals are broken, and Lilith allows Sam to kill her, thus breaking the Final Seal and setting Lucifer free. Throughout Season 5, Lucifer has command over nearly all demons. Dozens sacrifice themselves to assist him in raising Death. Others serve the Horsemen Pestilence and Famine, as well as the Whore of Babylon. Eventually, Lucifer is defeated and banished back to Hell.

In Season 6, in the aftermath of Lucifer's re-imprisonment, most demons have fallen under the command of Crowley, the current King of Hell. However, some demons, such as Meg, oppose his rule. Throughout Season 6, Crowley and his demons secretly assist Castiel in finding a way to open the doors to Purgatory in order to gain access to the millions of monsters souls inside. They succeed but Castiel betrays Crowley and absorbs all the souls for himself.

During the course of Season 7, the demons take a backseat to the Leviathans as the series' main antagonists. Under Crowley's orders, the demons refrain from attacking the Winchesters, so that the boys can defeat the Leviathans though the Winchesters come into conflict with rogue demons and ones hunting Castiel. However, with the death of the Leviathan leader Dick Roman at the end of the season, the demons are now poised to return to their original role as enemies of the Winchesters, having aided in finishing the last of the Leviathans on Earth.

At the start of Season 8, the Winchesters learn of a second tablet that holds the key to banishing all demons from Earth and closing the Gates of Hell forever. Their quest puts them in direct conflict with Crowley. Through the season, Sam and Dean come into conflict with the demons multiple times over Crowley's various goals. Eventually, after the Winchesters complete the first two of three trials needed to seal the Gates, Crowley keeps demons away from them to keep them from being used in the trial, but Sam and Dean capture him to cure him as the third trial. Crowley starts to become human, but Sam is convinced by Dean to stop after he learns from Naomi that Sam will die if he completes the trials. During the season, the Winchesters occasional enemy/ally Meg is killed. The demon Abaddon arrives in 2013 from 1958 and is defeated by Sam and Dean, but not killed. She eventually escapes after the Winchesters try to use her as the third trial and starts opposing Crowley's rule, wanting a "regime change." Sam manages to defeat her when she tries to kill Crowley, but she merely flees her vessel after it is set on fire with Holy Oil and is not killed.

In Season 9, Crowley is held captive by the Winchesters at the Men of Letters base and ultimately offers a deal in exchange for the name and location of every demon on Earth. At the same time, Abaddon has a ritual performed to have her vessel Josie Sands restored and begins a crusade to take over Hell and Earth. Her first attempt to kill the Winchesters fails thanks to the angel Gadreel. Abaddon has since been reshaping Hell in Crowley's absence, making it more chaotic and voiding all deals, taking the souls early. After Gadreel takes full possession of Sam, Dean makes a deal with Crowley to save him: in exchange for his freedom, Crowley helps Sam expel the angel. Crowley then starts a war against Abaddon for rule of Hell. To this end, he forms a reluctant alliance with Dean to find the First Blade, the only weapon that can kill a Knight of Hell. The two locate the retired demon Cain, the Father of Murder and founder and slaughterer of the Knights of Hell. Cain eventually agrees to help, giving Dean the Mark of Cain so that he can wield the Blade and the location of the First Blade which is at the bottom of the ocean.

Even though Dean understands that Crowley was just using him to get the Blade, the two maintain their alliance as they need each other to defeat Abaddon who is the greater enemy. Eventually, working together, the Winchesters and Crowley find the First Blade, but Crowley takes it until they can locate Abaddon as he doesn't trust Sam and Dean not to try to kill him. Dean becomes obsessed with hunting and killing Abaddon and Sam joins him in this after learning that Abaddon is stealing souls to create an army of demons loyal only to her. Abaddon, using Crowley's son Gavin as leverage, forces Crowley to help her trap and kill the Winchesters. Crowley leads them to the First Blade, but subtly warns Dean that it is a trap when telling them where to meet him. In a final confrontation, the Mark of Cain grants Dean immunity to Abaddon's power and telekinesis, allowing him to gain the upper hand and finally kill her.

Sam and Dean leave Crowley alive, but take the First Blade with them. Crowley however escapes with his son to spare him from returning to his time and dying. Crowley later reveals that Cain, the Father of Murder did not want to kill and committed suicide but the Mark of Cain proved too strong, forcing his return as a demon. The same thing happens to Dean who transforms into a demon.

In Season 10, Dean has become a demon. Crowley wants Dean to rule by his side, but Dean is uninterested and proves too out of control for even Crowley. As a result, Crowley helps Sam capture Dean and saves Castiel to help deal with him. Sam manages to cure Dean of being a demon and he returns to hunting with his brother. At the same time, with Abaddon dead, Crowley regains control of Hell and punishes demons who transgressed against him, particularly by serving Abaddon. However, Crowley grows bored of his role and has to deal with the appearance of his mother Rowena who tries to manipulate him to gain power but fails. Cain eventually resurfaces, but is killed by Dean with the help of Sam, Castiel and Crowley. Eventually, Crowley helps remove the Mark of Cain from Dean's arm, but comes under attack by Castiel who is under a spell while Amara is accidentally released.

In Season 11, Crowley has his demon minions take care of a young Amara, but they find her difficult and constantly hungry, going so far as to consume her demon nanny and anyone who upsets her. She eventually escapes.

Crowley later agrees to help Sam and Dean contact Lucifer. Crowley sends two demons to capture Rowena so she can look up a way to summon Lucifer using the Book of the Damned. The meeting ends with Lucifer escaping in Castiel's vessel and Rowena getting killed after having been secretly working for the archangel. Lucifer tortures Crowley until he becomes an obedient servant, while most of the demons willingly go back to serving him. A few go rogue for their own safety.

In We Happy Few, Crowley is back on the throne and asks the demons to join him defeat Amara to make Hell great again. Unfortunately, they laugh at him, saying he has made hollow promises 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.

In Season 12, the demons are back to serving Lucifer, with two shown taking orders from him and defiantly rejecting Crowley as their king. After Lucifer is defeated and presumably sent back to his Cage, the demons return to Crowley. Some are ordered to study The Cage and use its structure to presumably create chains that can bind Lucifer. A few years back, the demons also found Nick's body and restored it for future use.

It's also revealed that the Princes of Hell, long thought dead, are in fact still alive aside from Azazel who had been killed by the Winchesters years before. While on a mission for the British Men of Letters, the Winchesters come into conflict with and kill Ramiel. Shortly thereafter, another Prince, Dagon, begins working for Lucifer again as the protector of his son. Dagon was eventually killed by Castiel while he was empowered by Lucifer's son, leaving Asmodeus as the only living Prince of Hell.

Discontent with Crowley continues, and two demons do eventually discover Lucifer and try to free him, but neither are aware that Lucifer's true prison is his own vessel, which Crowley has complete control over. When Crowley presents the now submissive Lucifer to an assembly of demons, Lucifer secretly threatens them to obey him and not Crowley. One of the demons, Drexel, eventually offers to help Lucifer break free from the system which gives Crowley control over Nick's body. When Drexel succeeds, the demons flock back to Lucifer while Crowley is presumably dead.

Loyalty falls completely to Lucifer when Crowley does end up dead at his own hands, in order to lock Lucifer away. The throne is vacant as a result.

In Season 13, Prince of Hell Asmodeus takes the throne of Hell as a temporary substitute for the absent Lucifer. Asmodeus commands the demons to retrieve Lucifer's newly-born son Jack so the boy may inherit his legacy as heir to the throne of Hell and also set free the Shedim. Asmodeus' plans are foiled by Sam and Dean.