Casey was a demon possessing a bartender in Ohio. Unlike her other demon brethren, she did not do any direct harm to humans. She also was willing to follow Sam if he chose to lead the demon army. The demon possessing Father Gil is her husband.
Casey was a bartender in a small town in Ohio that was plagued by vice. When Dean saved a man in her bar, she flirted with him a little before he left. She later took Dean's friend Richie to the house her parents left her, where she revealed that she was in fact possessed by a demon and that she knew he was a hunter. When he attempted to attack her with a hidden knife, she easily subdued and killed him, having grown found of the body she possessed and not wanting it to be damaged. The next day she brought Dean there instead, intending to kill him as well, but he was a step ahead of her: having tracked the GPS in Richie's cell phone, he found the house, buried Richie, and made a Devil's Trap on the floor, concealing it beneath a carpet. He tried to banish the demon but before he could complete the ritual she caused a small earthquake, scattering the pages of the exorcism book and trapping Dean in the basement with her, waiting on either Sam or Casey's backup to arrive first. The two enemies decided to be civil with each other since they were at a stalemate (Dean could not banish her without his book and she could not hurt him while in the Devil's Trap), and struck up a conversation. Eventually, the two reached a sort of friendly understanding, or at least an amicable tolerance. Casey respected Dean's deal and Dean regarded her with a tolerance he does not afford demons. When Dean calls her evil, Casey responded that she did not kill anyone, simply saying that one can "nudge humans in the right direction and they’ll walk right into hell with big fat smiles on their faces". Casey identified herself as a true believer in Lucifer, comparing him to the Christian's God, and told Dean the Yellow Eyed Demon's name, Azazel, and that Sam was supposed to lead the demon army.
Father Gil ended up arriving first, having left Sam upstairs. She kissed him passionately after he freed her from the Devil's Trap and then told Dean that they had been lovers for centuries. When he wanted to kill Dean, she quickly begged Father Gil not to before Sam charged in with the Colt, killing him. Dean similarly hoped to spare her, but Sam fired a fatal shot at her before he could stop him.
Powers and abilities
Casey was a black-eyed demon. Her exact rank in Hell's hierarchy is unknown, but her own statements indicate that she was somewhere beneath Azazel in rank and would have served Sam had he chosen to take over leadership of Hell. She seemed to be a regular low-ranking demon.
- Spell-casting - Casey knew a spell which created strong winds and seismic activity. She was able to cast this spell from within a devil's trap non-verbally and with mere concentration.
- Invulnerability - Casey could not be killed by methods such as stabbing her vessel with an ordinary knife. However, she preferred not to have her vessel damaged because she admired the real Casey's body.
- Super Strength - She was able to effortlessly overpower Reggie and snap his neck a full 180 degrees.
- Possession - The demon Casey used the real, human Casey as her vessel.
- Immortality - Casey was centuries old.
- Devil's trap - Casey could not exit a devil's trap once she entered one. She could not access her innate powers while within a devil's trap, but could still cast spells and could do so non-verbally.
- The Colt - Casey was killed when Sam shot her in the chest with the modified Colt.
- Demon-killing knife - As the knife could kill all but the most powerful of demons, it could kill her.
- The First Blade - It can kill every demon in existence.
- Death's Scythe - It can kill almost everything in existence.
- Primordial entities - Amara, God, Death and the Archangels can annihilate Casey effortlessly.