I'm still confused on how Murder House and Coven is tied to all of this
Character Connections
Since the latest season of AHS is a crossover, there are a few faces definitely returning. For one, we know that Ben and Vivien Harmon (Dylan McDermott and Connie Britton, respectively) will be back as the family who initially moved into Murder House in Los Angeles in Season 1. Also back for more is Taissa Farmiga, who played the couple’s daughter, Violet, but based on
photos posted to Instagram from the set, she'll be back as her Coven character, Zoe Benson. She could, however, play multiple roles. Murphy-verse stalwart Sarah Paulson has appeared in every season of AHS, and according to the teasers for Apocalypse will be leading the current one, so actors taking on many characters will likely be standard this time around.
Speaking of, what is the plot of Season 8? Little is known (well, Murphy did say it would
be like The Love Boat, but that wasn't meant to be taken literally), but the essential premise seems to be that some mushroom-cloud type event has left the world in disarray and Paulson's Ms. Wilhemina Venable has created some sort of bunker where she's rebuilding civilization in her image. Then there are the witches from Coven—Paulson's Cordelia Foxx, Emma Roberts as Madison Montgomery, Gabourey Sidibe as Queenie, Lily Rabe and Misty Day, Frances Conroy as Myrtle Snow, Stevie Nicks as herself, the aforementioned Taissa Farmiga as Zoe Benson—who are likely there to either help or stop the antichrist.
Yes, the antichrist. So, at the end of Murder House Vivien Harmon had a baby. Well, two babies. One was stillborn (though kinda came back as a ghost?) and the other was super-cute and perhaps fathered by Rubber Man—the guy in the BDSM outfit in all the posters who audiences later found out was Tate (Evan Peters), the one-time perpetrator of a school shooting who had been dead for years and might be some sort of embodiment of evil. (Watch Murder House’s ninth episode, "Spooky Little Girl," for an explanation of the antichrist thing.)
At the season’s end, that baby was adopted by Constance Langdon (Jessica Lang), who was the reason behind a lot of the deaths at Murder House and discovered, when the boy was just three years old, that he’d murdered his nanny with a smile on his face. Rumor has it that Cody Fern (American Crime Story: The Assassination of Gianni Versace) will be playing the grown-up version of that baby in Apocalypse, and unsurprisingly is the one Kathy Bates’ Ms. Miriam Mead says "hail, Satan!" to in the show’s trailer.
Also of note are the name connections. The original residents of the Murder House, back in the 1920s, were Charles and Nora Montgomery. She was an East Coast socialite; he was a "surgeon to the stars" who went a little mad and Frankenstein-ed their dead son. Also named “Montgomery”? Emma Roberts’ witch Madison, who in Coven was a Hollywood starlet. Currently, there is no established connection between her and the other family, but of all the names she could've been given, it doesn’t seem that "Montgomery" would be an accident.