Abaddon was one of only two remaining Knights of Hell, the other being her retired mentor, Cain. Abaddon was single-handedly responsible for the extinction of the original Men of Letters. She arrived in the present through time travel in her hunt for Henry Winchester and the key of the Order of Letters he was entrusted with; she failed to retrieve it, with Henry's grandsons Sam and Dean Winchester taking it instead. However, upon discovering what Hell had turned into in her absence, ruled by Crowley, Abaddon dropped the hunt for the key and started a civil war to take over Hell and then remake the world as she saw fit—with herself as Queen of Hell, ruling over demons, angels, and humans alike. As part of her plan she had her few loyal demons pull the souls from innocent people to bring these souls to Hell and turn them into demons. After using Crowley to trap the Winchesters, Abaddon was defeated and killed by Dean with the First Blade after he overcame her powers with the Mark of Cain.
Abaddon was originally human, one of the first fallen human souls who turned into a demon in Hell. Abaddon is one of the first demons, though younger than Lilith and the Princes of Hell. She was personally selected by Lucifer, the creator of demons, to become a Knight of Hell.[1] Like other Knights, she was trained by the original Knight, Cain, and wreaked havoc on Earth for thousands of years. It is hinted that she had romantic feelings for Cain that he did not return.[2]
Eventually, Cain fell in love with a human named Colette and swore off his evil ways for her sake. Abaddon and the other Knights kidnapped Colette in 1863, with Abaddon hoping to sway Cain and have him rejoin her. While Cain slew the other Knights with the First Blade, he hesitated to attack Abaddon, as she was possessing his wife when he found her. His refusal to return to her prompted Abaddon to begin forcing Colette to twist her neck into grotesque angles, as if to break it, to spite Cain, stating that if she could not have Cain, neither could Colette. Right as Cain went to stab Abaddon with the First Blade, she left Colette's body, causing Cain to kill Colette instead. Though Cain wanted to find and end Abaddon for what she had done, Colette, in her last words, begged him not to kill anyone anymore and Cain honored her wishes by not seeking Abaddon out.[2]
In 1958, Abaddon was sent to make an example of Father Max Thompson after demons learned of his attempts to turn them back into humans. Abaddon killed Father Thompson on August 5, but not before the priest revealed to her his secrets under torture, including the fact that he had been working with a Men of Letters initiate named Josie Sands.[3]
Some time later, while working with demons to steal human souls, Abaddon possesses the Mother Superior of the St. Bonaventure Convent in Milton, Illinois. When Henry Winchester and Josie Sands arrived, investigating the murders committed by one of the soulless nuns, they manage to exorcise two of Abaddon's demons. Abaddon, however proved immune to the exorcism and knocked Henry out. She then planned to possess Henry to study and then destroy the Men of Letters, but Josie convinced Abaddon to possess her instead. Abaddon then ordered her demon to continue their work until the day she returns. Leaving with Henry, Abaddon also subtly threatened Julia Wilkinson into not telling anyone what had happened.[4]
Abaddon murders the elder Man of Letters in 1958.
On August 12, Abaddon attacked the Men of Letters headquarters during Josie's initiation ceremony, now seeking to steal the key to the Men of Letters bunker, which housed the greatest stash of secret knowledge and objects that Abaddon could use to incite mass chaos. She killed everyone at the Men of Letters' headquarters except for Larry Ganem and Henry Winchester, who was entrusted with the key (placed inside a box) for safekeeping. Henry used a spell to travel through time, with Abaddon quickly following after him once she burnt down the headquarters.[1]
Due to Abaddon's inexplicable absence, the denizens of Hell came to believe that she had been killed.[5]
Abaddon appeared in the year 2013 in As Time Goes By, where she was met by Henry's grandsons, Sam and Dean Winchester. Dean managed to stab her with the demon-killing knife, but while it hurt her, Abaddon survived, forcing the Winchesters to flee. After reading the memories of the motel clerk to learn what he knew about Sam and Dean, Abaddon killed the clerk and set off in pursuit of the Winchesters.
Abaddon traveled to the former location the Men of Letters' headquarters, which (as she was amused to discover) had been turned into Astro Comics after being rebuilt from the fire in 1958. She checked the memories of the clerk there to find out what Sam, Dean, and Henry had been there for. Abaddon liked the clerk's "The Devil Made Me Do It" shirt, so after killing the girl, the demon changed out of Josie's gown and pearls and stole the clerk's outfit.
Abaddon tracked the now blind Larry down and possessed his wife shortly before Sam arrived. She listened as Larry explained that the box opened the Men of Letters' highly important storehouse and gave Sam the coordinates to it. She then killed Larry and knocked Sam out before repossessing Josie's body. Abaddon called Dean and demanded that he trade Henry and the box for Sam's life, which he agreed to. She reneged on the deal by trapping Sam and Dean and mortally wounding Henry, who shot her in the head. Abaddon found the headshot to be a "rush," but her good humor instantly disappeared once she discovered that the box she was given was a fake. Demanding to know where the real one was, she tried to read Henry's memories, but was she unable to so much as move— as Dean and Henry had outsmarted her, and the bullet now in her brain had been engraved with a devil's trap. Dean then decapitated Abaddon, planning to cut her into small pieces and bury these pieces in cement to permanently trap her.
Abaddon sewed back together.
Sam and Dean retrieved Abaddon's body parts and sewed them back together in Clip Show. As a precaution, however, they did not reattach her hands, which were left in a nearby box. Abaddon deduced that Sam and Dean were planning to turn her back into a human to complete the third trial. When the brothers received a phone call from Crowley, Abaddon, who heard respond them to the call, was shocked to find out "the salesman" was now the King of Hell. Sam and Dean left the room to talk to Crowley, giving Abaddon the opportunity she needed: she had one of her hands climb out of its box, crawl onto her body, and remove the bullet from her head, thus enabling her to move again. By the time Sam and Dean returned, Abaddon had vanished.
After Crowley sent out a distress call in Sacrifice, Abaddon showed up with both of her hands now reattached. Using terrakinesis, she broke the devil's trap holding Crowley and flung Sam around before throwing the hunter out of a window. However, she was not there to save Crowley; instead, she was furious that, in the time she was gone, a mere crossroads demon had assumed leadership of Hell. She proceeded to beat Crowley and told him that she wanted a "regime change." But before she could do anything else, Sam returned, doused her in Holy Oil, and set her on fire, forcing Abaddon to escape from Josie's burning body.
In Devil May Care, she had a demon perform a ritual to restore Josie Sands's body for Abaddon to use. Once restored, she rallied several demons, convincing them that deals are not as important to hell's strength as fighting and conquering. Despite telling the group that Crowley had died, she met resistance from a Crossroad Demon who wanted more definite proof of Crowley's demise. After the demon tells her that she'd always thought the Knights of Hell were overrated, Abaddon sent her back to Hell merely by choking the human host, telling the demon, as she left her vessel, to spread the news in hell she (Abaddon) is "coming" (to rule them). Abaddon led her three loyal demons to a military base where she had them possess three soldiers; she and her minions then got her hands on three hunters: Pete, whom she used to learn more about the Winchesters, Irv, and Tracy; all three were used to draw the Winchesters to her. Abaddon confronted Dean and Tracy, but avoided being shot with more Devil's Trap bullets by wearing a bullet-proof vest; she also managed to disarm Dean of an Angel Blade when he tried to stab her with it. After dominating Dean, Abaddon threatened to possess him and make him witness all the atrocities she would commit unless he reveals the location of Crowley, promising to kill him quickly if he did so. However, when Gadreel reveals his true form nearby, Abaddon flees.
In Heaven Can't Wait, Crowley used a Goblet of Blood to contact Abaddon, who was amused by his call. Abaddon revealed that she has gone back on all of the deals Crowley had made and collected the souls early, doubling the amount of souls in Hell. She was also reshaping Hell to be more chaotic and claimed that since Crowley's disappearance, he did not have much support left. When Crowley threatened her, Abaddon told him she "cannot wait" and hung up on him.
Abaddon confronts Crowley.
Abaddon continued her campaign to control Hell. However, in Road Trip, she met some resistance from some demons, including her own escorts. Abaddon learned Crowley's location from a subordinate whom she killed after learning that she was also working for Crowley too. After finding Crowley her escorts refused to kill him on her commands, as Crowley still had much support from his original minions. Abaddon proposed a fight to settle the struggle but Crowley stated that it was not a fight but a campaign.
In First Born, when Dean and Crowley met Cain in search of The First Blade, Cain revealed his past with Abaddon and the other Knights and transferred his Mark to Dean so he could be the one to kill Abaddon, unwilling to break his promise to Colette to not go after her for revenge.
In Blade Runners, Abaddon learns of Crowley's search for the First Blade from the demon Lola who acted as Crowley's supplier; she begins her own search for the weapon to thwart Crowley's plans. She sends two demons to the Blade's last known location, but former Men of Letters member Magnus had already acquired it before Abaddon's demons could grab it. Abaddon's demon manages to track the Winchesters and Crowley to Magnus' hideout, but can't get in; instead, they vandalize the Impala with a threat in Enochian from Abaddon.
In Mother's Little Helper, Sam learns of Abaddon's actions in Milton in 1958 from Julia Wilkinson and realizes that the demon possessing Sister Agnes, Abaddon's remaining minion from that time, is once again continuing her work. Sam kills the demon and returns the souls, but not before learning that Abaddon is stealing souls to create an army of demons loyal only to her and that there are other places than Milton where this is happening all over.
In Meta Fiction, other hunters find signs of soulless people all over created by Abaddon's plans, but no sign of Abaddon herself.
Abaddon is killed by Dean Winchester with the First Blade.
In King of the Damned, Abaddon went back to 1723 and kidnapped Crowley's son Gavin MacLeod to force Crowley to help her trap and kill the Winchesters. At this point, even Crowley's most loyal demons have gone over to Abaddon's side; they help her find him. After Abaddon tortured Gavin before Crowley's eyes, the latter agreed and led Sam and Dean to the First Blade over the phone so they would go after Abaddon and fall into her trap. However, after telling Sam and Dean where to meet him to begin the "hunt", Crowley secretly warned Dean it was a trap with a secret code, something Abaddon didn't pick up on. Not wanting Crowley to be able to interfere, Abaddon shoots him with a bullet engraved with a devil's trap like Henry Winchester did to her to immobilize him and bind his powers. When Dean arrives alone, Abaddon pins him to a wall with telekinesis, pleased as she can finally eliminate the one major threat to her power. However, using the power of the Mark of Cain, Dean is able to fight through Abaddon's power and slowly advance on her. Abaddon regains power over him and pins him to the wall again, causing him to drop the Blade. Abaddon is amused by Dean's efforts to reach the Blade but is soon stunned when he displays telekinesis himself to get the Blade and then becomes completely immune to her powers. As Abaddon stares on in shock and Sam enters the room, Dean advances on her and stabs Abaddon in the stomach with the First Blade, lifting her off of her feet. The First Blade sends red energy coursing through Abaddon in a manner similar to a smiting, killing her. Dean then repeatedly stabs Abaddon's dead body with the First Blade, moved by the rage fueled by the Mark before being stopped by Sam.
In Stairway to Heaven, Sam tells Castiel about Dean killing Abaddon, saying she's dead "and then some", letting Castiel worried about the Mark of Cain's effects on Dean.
In Do You Believe In Miracles?, Crowley has regained full control of Hell. Dean, after summoning Crowley to find out what's wrong with himself, tells him that ever since he killed Abaddon, he's felt a constant need to kill and is getting sick when he doesn't. Metatron later mocks Dean for his attempts to kill him, stating that Dean killed Abaddon and then figured he could kill Metatron, but is wrong.
In Soul Survivor, Crowley punishes demons who have transgressed against him, particularly ones that have helped Abaddon. In particular, Crowley executes a demon who had coerced others into aligning with Abaddon and spread rumors and fostered doubt about Crowley's competence and authority.
In Girls, Girls, Girls, Gerald reveals that after soul deals were down following the war with Abaddon, he and Raul established a brothel to raise the number of deals. However, this method disgusts Crowley as tacky.
In The Things We Left Behind, when Dean falls back under the influence of the Mark of Cain, he flashes back on killing Abaddon and mutilating her body along with everyone else he hurt while possessing the Mark.
In The Executioner's Song, Cain explains that when Abaddon's forces went after him, he was forced to take up arms to defend himself and it resulted in him falling back under the Mark of Cain's influence. Cain has also heard about Abaddon's death at Dean's hands and comments on it to Castiel, asking if Dean is doing alright since he killed Abaddon. Dean, as he prepares to go kill Cain, tells Sam and Castiel that Cain had told him that once he killed Abaddon, he would have to kill Cain too.
In Inside Man, Dean has a nightmare of several of the people he has attacked under the influence of the Mark of Cain. Part of the nightmare includes when Dean killed Abaddon.
In Family Feud, Abaddon appears in a brief flashback to her abduction of Gavin MacLeod when Gavin tells the Winchesters and Rowena about his fiancé Fiona Duncan. When Gavin prepares to return to his time using the Blood Sigil, Dean mentions that their grandfather and Abaddon have successfully used the spell in the past.
In All Along the Watchtower, when questioned as to why he kept Lucifer from returning to Lucifer's Cage, Crowley tells the Winchesters he wanted to use Lucifer to finally win full control of Hell instead of having those like Lucifer and Abaddon try to take power from him.
Abaddon is untrustworthy, greedy, and quick to anger, but also very cunning. She adapts quickly, as she managed to use modern technology, weaponry, and armory to her advantage despite being here only a short time in the present. She is a brilliant strategist, able to secure several meatsuits and weapons for her subordinates in one move, as well as to locate and take prisoner two hunters who could be used as bait for the Winchesters, effectively luring them in and briefly overpowering them. She has a twisted sense of humor, seeming amused when she discovered that the Men of Letters' headquarters had been turned into a comic book store and then laughing when it seemed that Dean and Henry had fallen into her trap. She even went so far as to kill a girl and steal the clothes off the girl's corpse to dress herself simply because of the girl's ironic "The Devil Made Me Do It" shirt. Abaddon is extremely ambitious and power-hungry, even for a demon; she plans to not only take over as ruler of Hell, but also the world, forcing all demons, humans, and fallen angels to bow to her or be killed.
Although Abaddon enjoys causing suffering to others and basks in the fear her victims have of her, she prefers to kill her victims in quick, brutal ways and move on. She views killing as "art"; when comparing her murder of Father Thompson to her killing the Men of Letters, she judged how she slaughtered the Men of Letters to have been better, commenting that her killing of Father Thompson merely "got the job done." Additionally, she saw the act of killing her victims quickly as merciful, as opposed to torturing them over a longer period of time before taking their lives. The fact that she used torture to interrogate hunters in "Devil May Care" despite being telepathic and having the ability to simply extract the desired information from their minds suggests that Abaddon was either teaching her minions better techniques for torture, indulging her sadistic side, or a combination of both.
Abaddon flaunts her superiority over others. However her arrogance can cause her to underestimate and underplay her opponents, which was how she was defeated in As Time Goes By and Sacrifice and led to her death in King of the Damned. She has shown to be highly aggressive and has a tendency to attack those who do not show her enough respect. She beat Crowley up when he tried to command her and then insulted her by calling her a "whore". Similarly, Abaddon choked one Crossroad Demon who called the Knights of Hell "overrated", and sent her back to Hell as a warning to other demons. Abaddon values young attractive vessels and takes pride in possessing them, considering Josie Sands and Dean worthy vessels for herself. She arranged for her minions to possess young, fit, healthy vessels because she deemed them superior to the ones they had been using. She showed disdain at Larry Ganem's having aged.
As a Knight, Abaddon had a militaristic understanding of the role of the King of Hell: he or she must fight and conquer to add to Hell's possessions. She was appalled upon learning that Crowley, a crossroads demon - a "salesman", in her words - was the new King of Hell. She showed immense disdain towards him and his policies to expand the number of souls in Hell, which were based on deals and contracts, that is, exchange relations. Unlike Crowley, Abaddon does not care about deal-making; in her stint as Queen, she even violated Hell's contracts to reap earlier the souls of humans who had made deals with demons.
Likely, she began preparing to overthrow Crowley and take over leadership of Hell herself the moment she learned he was King. As she finds out more about what Hell and demon-kind had turned into in her absence, Abaddon expressed varying levels of shock, disgust, and even caustic amusement at the state of things. She believed that Crowley was the source of Hell's problems, stating that she and her forces will be hailed as liberators by other demons when they do take over.
For Abaddon, Hell could be improved by giving it a militaristic makeover. In a speech announcing herself as Hell's new ruler to a small group of demons, she criticized one of those present, a crossroads demon, due to her choice of vessel, an old woman, despite the fact that this had been a successful disguise for the demon in question. Abaddon banished the crossroads demon back to Hell due to her skepticism of Abaddon's leadership, and then led the remaining demons into possessing the bodies of U.S. Marines.
Crowley, on his turn, was himself contemptuous of Abaddon's overreliance on brute force and anti-intellectual disposition, arguing that she only appealed to dumber demons.
Despite her demeanor, Abaddon does display moments of fear and worry. A notable example was when she faced off against Dean when he had both the Mark of Cain and the First Blade in his possession. Despite taking joy in pinning the Winchester with her telekinesis, she was clearly concerned when Dean resisted it repeatedly until he ultimately managed to fight all the way through it. Abaddon also seems to be afraid of angels despite her desire to rule over the fallen ones as much as she does all Humans and Demons. This is evidenced by her look of anxiousness and nervous tone when asking Dean if what was nearby was actually an angel, leading her to flee instead of even attempting to fight one on her own.
Although Abaddon was a black-eyed demon, she was also a Knight of Hell, making her one of the most powerful demons to appear in the series. She displayed some powers that are either rare or unique among even high-ranking demons. Abaddon single-handedly slaughtered a group of Men of Letters elders with ease, despite their vast knowledge of magic. She also believed herself capable of killing Crowley, the former King of Hell, though Crowley also claimed that he could kill her. Despite Abaddon's power, she was vulnerable to some demonic weaknesses and was wary of fallen angels, refusing to fight even one on her own. Abaddon's screams (or even presence) were able to cause thunder and lightning to strike.
Biokinesis - Abaddon caused Larry's eyes to bleed heavily and leave him permanently blind. She was also able to cause Gavin MacLeod's eyes to bleed heavily for a few minutes, but stopped before it could cause permanent damage. She was even able to control her hands, when they were severed, as if they were still attached.
Immunity - Abaddon is the only demon so far known to be unaffected by exorcism rites; she is also able to walk on consecrated ground. She even survived being stabbed with the demon-killing knife, though she still found it painful. She is more resistant to holy fire than demons such as Meg, who was paralyzed when thrown onto a ring of holy fire, whereas Abaddon was completely engulfed in holy flames yet could still move.
Super Strength - Due to her status as a Knight of Hell, Abaddon has a high level of superhuman strength, even for a demon. Abaddon has the physical strength necessary to break a human's bones with only slight effort on Abaddon's part. When holding a man in place by his neck, Abaddon snapped it and killed him. She later slashed another man's throat just by striking him with her fingernails, and killed a third man by thrusting her hand into his abdomen to wound him seriously enough that he died soon afterward. When her hands were removed from her vessel, she threatened to "stump" the Winchesters to death. She was able to physically overpower Dean in a fight and hold him in place before bodily throwing him away.
Demonic Possession - Abaddon can only become corporeal on Earth by infesting and controlling a human's body; she does not need the human's permission to do this.
Memory Extraction - By inserting part of her essence into humans, Abaddon can access their memories (even their subconscious memories) to see and hear what they saw and heard. She seems to be able to instantly locate the memories relevant to what she wants to know. When she uses this ability, the eyes of the person whose memories she is reading cloud into gray. She cannot use this ability when in a Devil's Trap.
Teleproprioception - Even with a bullet carved with a devil's trap in her head, she could make her vessel's severed hand open the box it was in, move toward her, jump onto her body, and remove the bullet from her head. Abaddon is able to keep her vessel from dying or decomposing while she possessing it, no matter how severe the injuries.
Spell-Casting - Abaddon was able to travel through time to pursue Henry by replicating the effects of a blood sigil cast by Henry, despite her not being related to any of the Winchesters by blood. She later did the same to get Gavin MacLeod but did it using what was presumably Crowley's blood for the spell.
Telekinesis - Abaddon has the ability to move people and objects with her mind. Without even looking at them, she threw Sam and Dean into separate walls by raising a hand to both men. She later pinned Dean to a wall with no visible hand movements and kept him pinned there without even raising a hand. However, when he started to fight through her power, she used hand movements due to the amount of concentration involved in the effort.
Teleportation- Abaddon has the ability to teleport from one location and reappear in another.
Invulnerability - Abaddon cannot be killed by conventional methods, including being shot in the head or dismembered, nor does she appear to find injuries from conventional weapons very painful—when shot in the head, she laughed it off and declared it "a blast." However, she finds certain supernatural weapons and substances painful. She initially does not realize that her hands have not been reattached in "Clip Show" and must have Dean point it out to her, which suggests that she is not as attuned to physical sensation as humans are.
Immortality - Abaddon is an ancient demon, who was trained by Cain, which was thousands of years ago. She had the potential to live forever, had she not been killed. Even after Dean sliced her head off, Dean claimed that she was alive, just powerless, and made plans to slice her into small portions and bury her under tons of cement, so that she remained trapped and helpless.
Super Stamina - Abaddon is not subject to the needs that humans are. While decapitated and dismembered, she did not have access to food or water, yet did not die nor seemingly suffer any other consequence. When her body parts were reattached, Abaddon reacted as though she were waking up from sleep; however, she does not require sleep.
Terrakinesis - Abaddon has the power to create seismic activity. She broke a devil's trap containing Crowley by causing tremors that cracked the floor of the church Crowley was in. She did this before even physically arriving at the church.
Simply by touch, Abaddon exorcises a demon.
Flight - In her disembodied smoke state, Abaddon can fly.
Tactile Exorcism - Abaddon can expel another demon from its vessel and cast it back to Hell by choking said demon's vessel.
Despite being one of the Knights of Hell, thus making her one of the oldest and most powerful demons in creation, Abaddon possessed weaknesses common in all demons. However, due to her level of power, she is very difficult to truly harm or kill.
In order to stop Abaddon from getting control ofHell, the Winchesters formed an alliance with Crowley to kill her and Dean took on the Mark of Cain. Having learned of this, Abaddon used Crowley's son to lure the Winchesters into a trap in order to kill them and Crowley and destroy the First Blade. Having incapacitated Crowley, Abaddon attacked Dean at the Humboldt Hotel, but Dean was able to summon the First Blade back to him with telekinesis and become immune to Abaddon's power with help from the Mark of Cain. With Abaddon unable to affect him with her powers, Dean stabbed Abaddon in the stomach with the First Blade and lifted her off her feet. The First Blade sent red energy coursing through Abaddon's vessel in a similar manner to a smiting, killing Abaddon. Dean then mutilated Abaddon's corpse with the First Blade while under the influence of the Mark of Cain.
Abaddon is the Hebrew word for "destruction". In Revelation, Abaddon is called "The Destroyer."
In Jewish lore, Abaddon is simply a word for the afterlife (sometimes, of Hell itself). In Christian lore, however, Abaddon is a demon or fallen angel; in Revelation, he is known as "the angel of the bottomless pit" who rules over an army of demonic locusts that will torment people who do not have the seal of God on their foreheads, for five months. Some Christian traditions hold that Abaddon is actually the Devil himself. When personified as an actual entity in lore, Abaddon is male as opposed to the female Abaddon portrayed in Supernatural.
There was an angel in the novel Supernatural: War of the Sons named Abbadon who went by the nickname "Don." This angel guarded Lucifer's Cage and sent Sam and Dean Winchesterback in time. War of the Sons was published on February 9, 2011, two years before the demonic Abaddon was introduced on the show. Whether there is any correlation between the two characters is unknown.
Abaddon is among the most powerful demons to appear and seems to rank high in the hierarchy of Hell, but ironically she has black eyes, which usually designate a common, low-ranking demon.
John Winchester once interrogated and exorcised a demon who had served Abaddon. The demon also told him and Tara of The First Blade, the only weapon capable of killing Abaddon, but John never believed in it. John wrote a bit of this down in his journal and a file in his lock-up.
Larry Ganem described Abaddon as a "hired gun" in As Time Goes By. This indicates that she was working for someone or something more powerful in 1958. When asked how to stop her, he states that she can't be stopped.
It seems that Abaddon enjoys injuring her victims' eyes: she blinded Larry and Crowley's son, Gavin, by making them bleed heavily from their eyes, and expressed excitement at the idea of tearing out Dean's "pretty green eyes."
Abaddon has shown an unusual attachment to using Josie Sands' body as her own. She has twice returned to Josie's body after vacating it, even arranging for one of her minions to reconstitute it using a ritual. Abaddon herself did not even take a new vessel to perform the ritual herself, instead remaining in disembodied form and waiting for Josie's body to be restored so she could possess it.
Apparently Abaddon had developed feelings for Cain somewhere in the past as she showed jealousy towards Cain's wife Colette as shown in First Born. It is possible she was attracted to his power.
Abaddon is the third main antagonist killed by Dean Winchester, the others being Azazel, Dick Roman and Lucifer. However, she is the first he's managed to kill in a straight up fight (having the Mark of Cain with the First Blade) without trickery or outside assistance.
Abaddon's escape in Clip Show and following war to take over Hell is partially Sam and Dean's fault: they let her know that Crowley now ruled Hell, apparently sparking her ambition to take it over herself and they didn't properly secure her with a devil's trap, relying on the bullet in her head to keep her imprisoned. This allowed her to escape while they were distracted and start a Hell's Civil War.
With the deaths of Abaddon and later Cain as well as Dean being cured, the Knights of Hell are now extinct.
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