Abaddon, primarily played by actress Alaina Huffman, is a character in the television series Supernatural.
Abaddon is described as the last remaining Knight of Hell, a class of mighty demons who were among the first of their kind. Abaddon is too strong to be affected by exorcisms or to be killed by Ruby's knife. She is introduced in the eighth-season episode "As Time Goes By," in which she is sent to destroy the Men of Letters organization in 1958 and sets off in dogged pursuit of Sam and Dean's grandfather, Henry Winchester, who has escaped with the key to the Men of Letters' bunker. Wanting to break into the bunker to gain access to the powerful supernatural spells and artifacts inside, Abaddon follows Henry through time to the present and hunts him and his grandsons throughout the episode. She takes Sam hostage to force Dean to turn over Henry and the key but reneges on her deal to let Sam and Dean go after Dean trades her Henry and the key.
In the confrontation that follows, Abaddon mortally wounds Henry, but not before he shoots her in the head with a bullet engraved with a devil's trap that binds her powers and also binds her to her now-paralyzed host body. Sam and Dean then cut her up and bury her in cement to forever entomb her. In "Clip Show," Sam and Dean need a demon to cure to do the third trial to close the gates of Hell, so they sew Abaddon back together to use her, without reattaching her hands or removing the bullet. Abaddon reveals that she had been sent to kill the priest who found a way to cure demons and that while torturing him, she found out about the Men of Letters (including her host Josie Sands) from him. This ultimately resulted in her possessing Josie and attacking the Men of Letters. While Sam and Dean take a phone call from Crowley outside, Abaddon frees herself and escapes by controlling one of her severed hands and using it to remove the bullet from her skull. In the following episode, the season finale "Sacrifice," she arrives in response to Crowley's distress call but attacks him rather than help him, furious that Crowley now rules Hell and declaring her intention of taking over herself, only to be driven away when Sam sets her ablaze in holy fire.
Abaddon returns in the ninth season, her objectives now to kill Crowley to become the Queen of Hell and "turn all of humankind into her demon army." With Crowley being largely absent from Hell and having been deeply affected by the incomplete demon cure forced on him by the Winchesters, the intimidating Abaddon ends up winning the nearly unanimous support of other demons.
In "First Born," Crowley and Dean go to her maker, teacher, and former lover, Cain, to get his Mark. The First Blade from him—the Blade, when wielded by someone bearing the Mark of Cain, is stated to be the only weapon capable of killing Abaddon—and Cain reveals that Abaddon, after failing to persuade him to rejoin her, had tricked him into murdering his beloved human wife Colette; as he is unable to seek revenge directly due to a promise he had made to Colette, he gives Dean the Mark so that Dean can kill Abaddon once Crowley finds the Blade.
"Mother's Little Helper" reveals that Abaddon's history with the Men of Letters goes back further than previously thought, as Abaddon had been confronted by Henry and Josie when stealing people's souls at a convent sometime before her slaughter of the Men of Letters. She intended to possess Henry to spy on the Men of Letters before destroying them but accepted Josie's offer and possessed her instead, all without Henry's knowledge. In the present, Abaddon has given the order for her minions to begin stealing souls again to build an army of demons loyal only to her. In an attempt to eliminate all threats posed to her and her rule, Abaddon concocts a plan to kill Crowley and the Winchesters and to destroy the First Blade by first bringing Crowley's human son Gavin forward in time and torturing him until Crowley agrees to help her set up a trap for Sam and Dean. She has him send the Winchesters to retrieve the First Blade and then lead them to her so that she can destroy them all at once, though Crowley manages to warn Dean of the trap subtly. Although unaware of the double-cross, Abaddon incapacitates Crowley by shooting him with a devil's trap bullet to keep him from interfering in the upcoming fight, planning to kill him and his son once she has killed the Winchesters. She is slain by Dean wielding the First Blade when Mark grants Dean new powers that enable him to overcome her attacks. Following Abaddon's death, all demons go back to following Crowley. Despite this, some demons remained loyal to her and outraged at Dean killing her, try to ambush him in "Black" only to be easily killed themselves.
Executive producer and series writer Adam Glass revealed on Twitter that his inspiration for Abaddon was Lauren Bacall, an actress whom he admires. Showrunner Jeremy Carver went into the character's motivation, explaining that Abaddon was "appalled" to find that Crowley ruled over Hell because she "loves Hell and what it represents." He believed that the contrasts in the two characters' views incited "a nice conflict to our demon world."