Much later in the season, we get the full rundown from our resident psychic diva, Billie Dean Howard. When Constance asks what happens when a spirit impregnates a woman, Billie shares the story of the Antichrist.
"When a new Pope has been chosen, and the bells of St. Peter's chime, he is shown into a small chamber next to the Sistine Chapel. They call it 'The Room of Tears,' named for the sublime mixture of joy and sorrow that he must contemplate at this moment. He is brought a key to this box. It has been said that this box contains the ultimate secret. It holds the secret of the end of the world . . . This piece of paper reveals the precise nature of the Antichrist: a child born of human and spirit will usher in the End of Times. It is the essence of evil. A perversion of the Immaculate Conception."
In this moment, we have all the information we need to understand the nature of Murder House. It's not just about the unfortunate end of the Harmon family. It's about the beginning of the end of the world as we know it.