Apocalypse (as Well as Murder House and Asylum): Satan/The Devil
The devil is more omnipresent than concrete, but he does get a shoutout throughout many American Horror Story seasons. He's first a presence in Murder House, prompting the conception of Michael Langdon, who brings on the apocalypse in season nine. He also wreaks havoc on Briarcliff when possessing Sister Mary Eunice. In 1984, he resurrects Richard Ramirez from the dead.