- “There’s a saying where I come from: Hold hands with the devil until you’re both over the bridge. I haven’t found the other side of the bridge yet.”
Cosmina worked for Sean, a dealer of demons, under the justification that his scheme kept the supernatural population in Dublin under control, as well as assisted her with bigger threats. Although, she wasn't aware she had been eliminating his supply of zompires, and, for this, she was imprisoned and used in the fight club at O'Hannigan Ironworks.
Having dreamed of Cosmina, the also Slayer Athena Jamison-Smythe found her in the middle of a fight to the death against multiple adversaries, so she jumped into the arena to assist her. Cosmina taught her how to slay zompires, but she left Nina in the fight alone as soon as she had a chance to leave. She went after the vampire who had imprisoned her, and beheaded her with a stake.
As they met after the fight was finished, Cosmina showed Athena her mangled ear and scarring that went down her neck, which she attributed to another Slayer. She also complained about the Slayer dreams she had of Athena being left at a house fire.