Crowley

Fergus Rodric "Crowley" McLeod was the right-hand man of Lilith and King of the Crossroads Demons. It was revealed by Becky Rosen that Bela Talbot didn't give the Colt to Lilith like she said, but actually gave it to him. Unlike other demons, he is not loyal to Lucifer because Lucifer is an angel and Crowley realizes that Lucifer doesn't care about demons at all and believes that if Lucifer destroys humanity then demons will be next. He ultimately wants Lucifer dead so things will go back to normal before the Apocalypse happened. He forms an alliance with the Winchester brothers by giving them the Colt and when it fails to kill Lucifer, he then proceeds to help the brothers get the rings of the four horsemen to put Lucifer back into his cage. After Lucifer was resealed and with Lilith dead, Crowley was made King of Hell. As King of Hell, he wishes to gain the souls in Purgatory and has made an alliance with Castiel with the promise of splitting the souls in Purgatory fifty-fifty.

Season 5
At the end of "The Real Ghostbusters", Becky Rosen tells Sam that there is a scene in Chuck's books that reveals that Bela Talbot lied to Dean when she told him that she gave the Colt to Lilith. The scene in the book explains that Bela actually gave the Colt to Lilith's right-hand man, Crowley.

Crowley first appears in "Abandon All Hope...", when he appears behind a banker that has summoned a crossroads demon. The man is at first very confused due to the fact his previous negotiations about his deal with a young, attractive woman. Crowley explains to the banker that he is a "big fish" so he did him the honor of coming personally to seal the deal. As Crowley and the banker kiss to seal the deal, they are being spied on by Castiel from a distance. Castiel tails Crowley when he leaves but he is stopped due to Crowley's home being protected by Enochian sigils. Later, the Winchester brothers, with the help of Jo, kill Crowley's two demon guards at the front gate and enter his home, while he's watching television. The Winchester brothers cut off the power to Crowley's home and then confront the demon. Crowley begins to walk toward the brothers, but stops as he realizes that they drew a devil's trap underneath a rug. As he turns over the rug and reveals the devil's trap, two demons sneak up behind Dean and Sam and restrain them. Crowley pulls out the Colt and then shoots the two demons.

Crowley explains to the brothers that he wants them to kill Lucifer with the Colt. Dean, who doesn't believe him, asks Crowley why he would want Lucifer dead. Crowley answers that Lucifer is an angel, whose well known for his hatred of humanity, he then asks the brothers if Lucifer has this much hatred for humanity then what are his feelings towards demons. Crowley continues saying that Lucifer thinks of demons as only servants and that once he destroys all of humanity, demons will be next. He then gives Sam the Colt. Sam then asks Crowley about the whereabouts of Lucifer to which he answers that he's in Carthage, Missouri. Sam then thanks him and fires the Colt at his head, only to learn that it has no ammo. As Crowley searches for more ammo, Dean asks him that by helping them isn't he signing his own death warrant and what he'll do if they fail to kill Lucifer. Crowley explains that Lucifer is going to kill all demons anyway and that he'll be going into hiding as soon as he is done helping them. Crowley then throws bullets to the Colt at Dean and teleports away.

Crowley later return in The Devil You Know, when he pops into the Impala. Sam claims Crowley knew the colt won't work, but Crowley shoots this down. He expresses his anger of the fact that now he has to hide from all the demons. He also tells them he can help them with the hunt for the horsemen (he was eavesdropping on them). He takes them back to his hideout and tells them he doesn't excalty know where the horsemen are, but he knows someone who does. So he and Dean headout to a company where the handler is. Crowley takes out the men in the main floor and sends Dean up to the handler with a "deal". When the "deal" backfires, and the handler gives chase, and Crowley knocks the handler out. While driving, Crowley craves a symbol into the handler's chest so he can't escape his meat suit.

Crowley later reveals that the handler, is in fact someone Sam knows, and Crowley wants to take this to another location. When they return, Crowley tells Sam he didn't want to bring the guy back, but Dean trusted Sam. With Brady tied up, Crowley tries to make a deal with Brady, but he refuses. So Crowley goes to demon nest, kills them all, but one, and "lets" it slip that he and Brady are, "Lovers Againist Lucifer". Brady now cooperates. Then Hellhounds come when Crowley got followed, and he disappears. When he comes back, he brings his own hellhound, which is bigger. Crowley later shows up at Bobby's to make a deal to find Death.

In Two Minutes to Midnight, Crowley shows up when Sam and Dean mention Bobby's deal, and Crowley shows them a picture of him and Bobby kissing. As they as about to head out, Crowley remarks about Bobby sitting, when he can do something. It seems in the deal to sell his sold, Crowley threw in Bobby's ability to walk as well. Now with Bobby walking again, he and Dean head out after death. Crowley gives Dean death's scythe he got from a deal to cut death's ring off. They head to chicago, and Crowley finds Death in a pizza parlour after the first location was a dud. With death location, Crowley vanishes.

Season 6
In the episode "Weekend At Bobby's", Bobby summons Crowley so that he can give him back his soul, as he had given it to him in the previous season in exchange for his help in putting Lucifer back into his cell. Bobby reminds him of this, and asks him to hold up his end of the deal, only to have Crowley refuse. Bobby, having anticipated this, turns off the lights, revealing a devil's trap that he had painted in the floor using glow-in-the-dark paint. Despite being trapped, Crowley reveals that he is being accompanied by a large Hellhound, forcing Bobby to release him.

After capturing and torturing a Crossroad Demon, Bobby learns two things: the first is that Crowley is currently the King of Hell, and Crowley's real name from his life as a human: Fergus McLeod. Bobby then uses Crowley's name and other clues to find out more about his background. With some help from fellow hunter Rufus Turner, he learns that he was born in Scotland in 1661, and he had a son, Gavin, who was the captain of a ship that went down. But, they recovered Gavin's ring, which is on display at a museum in Andover, Massachusetts. With some difficulty, Rufus is able to give the ring to Bobby, who uses it to summon the spirit of Gavin.

He then summons Crowley once more, trapped under a devil's trap drawn on the ceiling. When Bobby notices that he appears slightly disheveled, Crowley tells him that being King of Hell is not as fun as he thought that it would be, seeing that Demons are inherently destructive beings who don't want to listen to him and help him make things better, ironically being able to see why Lucifer hated them so much. After refusing once again to return Bobby's soul, Bobby reveals Gavin. But, after a faux display of affection, he reveals that he cared nothing for his son. Bobby says that he knows that, but says that he and Gavin had a long talk and that Gavin was willing to tell him all about Crowley. It's revealed that in life, Crowley was a tailor who made a deal with a Crossroad Demon to get "an extra three inches below the belt". He also reveals that Gavin told him where Crowley's mortal remains are buried, and hands him a phone. On the other end is Dean, who is with Sam in Scotland, having flown there to dig up Crowley's bones and torch them if he doesn't give Bobby back his soul.

Realizing he has been tricked, he gives back Bobby his soul -- leaving in the part of contract that allows Bobby to walk-- and after he is released, he teleports to Scotland to retrieve his bones. In Family Matters, Crowley tells the Winchesters he was the one who brought Sam back from hell. With Sam on the line, he makes the Winchesters work for him. In All Dogs Go To Heaven, Crowley approaches the boys give them a job to go after the alpha skinwalker.

In "Caged Heat", the facility where Crowley has been hiding and torturing the Alpha creatures is discovered by the Winchesters through Samuel. Making a deal with the demon Meg, who has a grudge against Crowley, the boys and demon infiltrate the facility, only to be double-crossed by Samuel. Samuel then reveals that Crowley plans to resurrect Mary Winchester in exchange for his help. After escaping their prison and freeing Meg from torture, the trio trick Crowley into a Devil's Trap, leaving him at their mercy. Keeping their deal, Meg tortures him for the boys, trying to force him to retrieve Sam's soul. In the midst of their conversation, Crowley gets Meg to step in the circle accidentally and breaks free allowing him to throw the Winchester brothers against wall. As Crowley gloats over his apparent victory, Castiel reappears with a bag containing Crowley's bones. After asking one more time about Sam's soul being returned, Crowley is deemed unhelpful and useless. Castiel then promptly sets the bones ablaze, leaving Crowley nothing but a pile of ash.

Eve later reveals that Crowley, is very much alive, and torturing creatures for thier souls. Sam and Dean have no idea how Crowley could be still alive. Near the end of Mommy Dearest, Crowley appears before Castiel, and complains about having to clean up Castiel's messes. Crowley is revealed to be Castiel's partner in crime. When Castiel comes to check on Crowley's progress, Crowley asks Castiel to get rid of the Winchesters, but Cas refuses. So later Crowley sends his goons after the Winchesters, but Castiel saves Sam, Dean and, Bobby. When the gang later figures out about Castiel and trap him, Crowley sends demons to the location. So with the oncoming demon threat, the Winchesters and Bobby flee, leaving Castiel trapped fire. Crowley arrives on scene and frees Castiel.

In Let It Bleed, Crowley makes his move and kidnappes Lisa and Ben. Crowley talks on the phone with Dean. He tell Dean that Lisa and Ben will be fine as long as Dean stops chasing him. If Dean continues to, Crowley will harm them. Castiel later confronts Crowley on kidnapping Ben and Lisa. He also tells Crowley he should have told Castiel first. Crowley laughs at that and tells Castiel he rather ask for forgiveness than permission. He also points out that the Winchester will be pre-occupied with him instead of Castiel. For insurance, Crowley has a demon possess Lisa.

In The Man Who Knew Too Much, Crowley and Castiel meet up and Crowley has everything ready. Then Castiel double crosses Crowley and tells Crowley that he won't give him any souls. Crowley is angry but Castiel gives two opitions, flee or die. Crowley chooses flee. Later Crowley comes back in force, and Castiel tries to kill Crowley with a touch, but it doesn't work. Crowley reveals his new ally, Raphael, and gives Castiel the same options Cas gave him before: flee or die (in a mocking tone). Castiel tosses him the jar of blood and leaves.

When the time comes, Crowley conducts the ritual, but nothing happens. Then Castiel reappears, and Crowley figures out that Castiel gave them the wrong blood (they used dog blood instead), and conducted his own ritual. Crowley sarcastically asks Castiel how his ritual went, Castiel shows him in a burst of white light. Crowley then makes his exit. Castiel says that he has plans for Crowley when Raphael asks why he allowed the demon to escape and not his angelic brother.

Season 7
Crowley is hiding away in an angel-proof room when Castiel finds him. As he braces for Castiel to kill him, Castiel tells Crowley that he needs Crowley to go back to being the king of Hell for balance. With no other option, Crowley accepts. He is later summoned by Sam, Dean and Bobby, and they ask him about how to bind Death. He doesn't tell them due to his new boss, but secretly send them the ritual.

Powers / Abilities
Crowley was one of the most powerful demons Sam and Dean faced throughout the series. It is possible that Crowley might have been a white eyed demon like Alastair and Lilith (since there was no on-screen event in which he reveals his demonic eyes). In Caged Heat, he is shown to be adept in torture.
 * Telekenesis
 * Wish Granting
 * Advanced Teleportation
 * Control over Hellhounds
 * Magical Knowledge (Hexed an entire building in order to detain Meg inside her vessel)
 * Invisibility
 * Pyrokinesis

Relationships

 * Lucifer (Father, Creator)
 * Demons (Siblings, Subordinates)
 * Lilith (Possible Lover, Superior, Demonic Sister)
 * Gavin MacLeod (Son [as a human])

Season 5

 * "Abandon All Hope..."
 * "The Devil You Know"
 * "Two Minutes to Midnight"

Season 6

 * "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"

Trivia

 * Crowley can be considered the main antagonist of the sixth season.
 * The character may be based on real-life Aleister Crowley, an occultist.
 * The character may be based on the demon Crowley who worked with an angel to prevent the apocalypse, as depicted in the book "Good Omens: The Nice and Accurate Prophecies of Agnes Nutter, Witch" by Terry Pratchett and Neil Gaiman.