Later this week, Kathryn Hahn makes her Marvel Cinematic Universe debut when WandaVision starts streaming on Disney+, and for the first time, the actress is opening up about her mysterious character “Agnes” and what it’s like joining the ambitious project that will bend reality as it hurtles through decades of classic TV. While not much is known about Hahn’s Agnes, some Marvel fans are convinced that she’s secretly Agatha Harkness, an ancient sorceress from the comics who’s both mentored the Scarlet Witch and been her adversary. In short, the two characters have a history together, and in a new interview, Hahn reveals that WandaVision will go deep into the Scarlet Witch’s “dark” and “traumatic” backstory, which is what drew Hahn to the project.