Apocalypse, which will premiere on FX on Sept. 12, will act as a crossover between American Horror Story: Coven and American Horror Story: Murder House.
Britton and McDermott previously portrayed married couple Vivien and Ben Harmon in Murder House, and were last seen turning into ghosts. Vivien, before she died, had given birth to Michael who is believed to be the Antichrist. Michael will be playing a role in Apocalypse and will be an adult portrayed by Cody Fern.
The cast also features returning Coven stars Sarah Paulson, Lily Rabe, Emma Roberts, Frances Conroy, Gabourney Sidibe, Stevie Nicks and Taissa Farmiga. They will be joined by Kathy Bates, Jessica Lange, Evan Peters, Cheyenne Jackson, Billy Eichner, Leslie Grossman and Billie Lourd.
The main theme of Apocalypse will be the end of the world, with the new season starting with a disastrous event. "The story begins with the end of times," executive producer Alexis Martin said to The Hollywood Reporter. "It starts in the real world. It's very tangible, and it's a familiar panic."