The Addiction Demon is a strange figure that appears randomly at the hotel. According to James March, it was brought into existence by Sally and various other drug addicts that patronized the hotel and used it to shoot up drugs. It was further revealed that the demon needs to feed on various victims in order to survive.
Personality and Appearance
The demon is sexually violent and aggressive. It doesn't have eyes or a mouth. Its skin is pale white and greasy, as if it is made of wax. It has a strap-on conical drill-bit dildo that it uses to assault its victims.
The Addiction Demon first appears in Room 64 after Gabriel takes drugs. At first, it appears to him from the shadows as a blurry vision that he assumes is a result of his high, but it quickly becomes apparent that this is not the case. As the demon gets closer to him, reaching out its bony fingers, Gabriel is disturbed and attempts to leave, only for it to appear in front of him and violently throw him against the mattress, pulling his pants down and raping him with its metal cone dildo. Sally slowly enters the room while Gabriel is screaming. She sits on a chair next to the bed and tells Gabriel to say "I love you, Sally" if he wants the demon to go away. After saying it, the Addiction Demon stops and disappears , causing Gabriel's eyes to dilate and body to remain motionless.
After a long day at work, John Lowe comes back to the hotel and tries to sleep on his bed. However, the alarm clock turns on and starts playing jazz music, shortly after followed by the TV, which turns on by itself and emits nothing but white static. After turning the alarm clock off, he attempts to go back to sleep, only to open his eyes and see the demon watching over him, its long fingers twisting and body hemorrhaging as its metal cone dildo whirls above his head . John jumps from the mattress, scared of the sight, but sees that nothing is there.
Claudia arrives at her room while talking on the phone with a friend. After hanging up, she dresses in her nightgown and goes to the bathroom to prep for bed. While there, she hears strange, gurgling-ike noises and witnesses the demon watching her from the reflection of the mirror, which causes her to drop her back to the wall and fall against it in fear. Later, when Sally tries to seduce John in the elevator in order to prevent him from trying to arrest her, she massages his penis, during which the blurry demon can be seen surrounding them while the lights go on and off. 
While James March argues with Sally for not trying to save John Lowe during his attempt to hang himself, the demon appears all around them at different intervals, causing the hallway lights to flicker. 
When John completes the Ten Commandment Killings, therefore finishing the legacy of James Patrick March, Sally attempts to kill him with a knife so that he can remain with her for eternity as a ghost, but is rebuffed by him. The demon, all the while, can be seen manifesting itself all around them.
March states that he at one point unleashed the demon on Sally to punish her for disobeying him. 
The Addiction Demon is a very powerful spiritual entity with a variety of supernatural powers.
- Immortality - As a demon, The Addiction Demon is not susceptible to human weaknesses, thus being immune to all aging, disease, and death.
- Transmutation - The Addiction Demon can move instantaneously from one location to another.
- Interdimensional Travel - The Addiction Demon can move freely through different dimensions, though its true physical forms seem to be limited to hellmouths.
- Mirror Travel - The Addiction Demon can appear inside of mirrors and stare out at individuals from behind the glass.
- Shapeshifting - The Addiction Demon only seem to be able to physically manifest in the mortal world if they are in a hellmouth, or a gateway into Hell itself. As a result, The Addiction Demon living inside of hellmouths exist indefinitely as a tangible personification of a fatal flaw in humanity, torturing Sally McKenna and other drug addicts in Hotel Cortez for their substance abuse.
- Intangibility / Invisibility - As a spiritual entity, The Addiction Demon has the ability to become tangible / seen or intangible / unseen at will.
- Immunity to Timeline Alteration - Unlike humans, but like other demons, The Addiction Demon seems both aware and unaffected by the alteration of timelines.
- Cosmic Awareness - The Addiction Demon knows and understands what's transpiring across the universe.
- James March (to Sally)
This demon that you and your kind have conjured with your diseased acts must feed. If not on others, then on you, dear Sally.
- The Addiction Demon (or something bearing resemblance to it) appears in the Hotel teaser "Do Not Disturb".
- The Addiction Demon is the second demon to appear in AHS.
- The Addiction Demon is the eighth immortal character to be introduced in accordance of each season; The first and second were Shachath and The Devil. The third was Marie Laveau. The fourth was Delphine LaLaurie. The fifth was Bastien. The sixth was Papa Legba. The "seventh" were a handful of vampires. The ninth was Scáthach.
- Demons are always drawn to negative energy, which explains why the Addiction Demon appears in the Hotel Cortez.
- In "Could It Be... Satan?", it is revealed that the Hotel Cortez is a "hellmouth", or gateway into Hell itself, thus implying that the Addiction Demon may have originally hailed from somewhere in the depths of the underworld and appeared to Sally as her personal tormenter.