In 1958, the Knight of Hell Abaddon set up a demon factory, a place where she'd steal people's souls to transform them into demons loyal to her. Along with three other demons, Abaddon took over St. Bonaventure Convent, possessing the Mother Superior while the three other demons possessed nuns, one of which was Sister Agnes. The demons began stealing souls from people with one of their victims, Sister Mary Catherine, killing two people before killing herself.
Sister Mary Catherine's actions draws the attention of the Men of Letters who, believing it to be a simple case of demonic possession, send initiates Henry Winchester and Josie Sands to investigate as a final test before they become full members of the order. Dressed as a priest and a nun, Henry and Josie claim to what they believe to be the Mother Superior and Sister Agnes that they were sent by the Office of the Inquisition to investigate Sister Mary Catherine's actions. Continuing to pose as the Mother Superior, Abaddon allows Sister Julia to guide them as they investigate. Sister Julia leads Henry and Josie to Sister Mary Catherine's room where Josie discovers the crest of the Knights of Hell which Henry recognizes as meaning trouble.
That night, Sister Julia spots Abaddon dragging another victim to the basement to have their soul stolen and is captured by Sister Agnes. The demons remove the souls of all the other kidnapped people, but before they can get Sister Julia's, Henry and Josie burst in and attack the two other possessed nuns while Abaddon and Sister Agnes are in the other room. Holding the two possessed nuns off with holy water, Henry and Josie each exorcise one of the demons.
Moments after her two minions are exorcised, Abaddon enters the room and Henry attempts an exorcism on her as well but she is immune to exorcisms. Abaddon flings Henry into a wall, knocking him out and confronts Josie who is disgusted by Abaddon's implication that she and Henry are hunters. Under threat to Henry, Josie explains that they are Men of Letters, amusing Abaddon with the fact that there is a woman amongst the order. Abaddon decides to possess Henry in order to study the Men of Letters up close, but Josie begs her not to and to possess Josie instead. Abaddon is amused by Josie giving her her permission, realizing that its because Josie loves Henry. Abaddon decides to do as Josie asks and abandons Mother Superior in favor of taking Josie as her vessel.
Sister Agnes, having witnessed the exchange between Abaddon and Josie, asks if Abaddon really intends to study the Men of Letters. Abaddon confirms she intends to do so after which, she'll destroy them. Abaddon orders Sister Agnes to keep their work going after she leaves and to "play dead." With Sister Agnes pretending to be exorcised, Abaddon is able to successfully fool Henry into believing that she's Josie and that Henry and Josie defeated the demons.
Still secretly possessing Josie, Abaddon tells the nuns not to tell anyone what happened at the convent and subtly threatens Sister Julia who was rescued by Henry and Josie before her soul could be taken. Abaddon leaves with the oblivious Henry and is able to successfully infiltrate and massacre the Men of Letters using Josie's body.
In 2014, during her war to take control of Hell from Crowley, Abaddon's demon factory at St. Bonaventure catches the attention of Henry's grandson Sam Winchester. Sam learns of the events in 1958 from the now-former Sister Julia and stops the demon factory once and for all, but not before learning its purpose and that Abaddon now has such factories all over the place.
- Final time a full exorcism is seen to date.
- Presumably takes place between August 5 and August 12 of 1958 as Henry and Josie are close to initiation and in Clip Show, Abaddon tells Sam and Dean she learned of Josie and the Men of Letters from Father Max Thompson who she murdered on August 5.
- These events are an indication that Abaddon has been planning to take control of Hell for a long time given the purpose of her demon factories was to create demons loyal only to her.
- Abaddon is once more shown to be immune to exorcisms.