WandaVision’s episode 7 teases that Agatha Harkness (Kathryn Hahn) may be secretly linked to Dormmamu, the inter-dimensional being and ruler of the Dark Dimension previously featured in Doctor Strange, instead of Mephisto. While WandaVision may have confirmed that Wanda’s (Elizabeth Olsen) neighbor Agnes, aka Agatha Harkness, has been manipulating Wanda and the citizens of Westview from behind the scenes (via her theme song “Agatha All Along”), Agatha’s motives and her involvement in the creation of the Hex is still unclear, allowing for the possibility of a second villain.
The most popular theory regarding that possible second villain involves Mephisto, the Marvel Comics equivalent to the devil. While Agatha Harkness and Mephisto were never allies within the comics, both characters are indirectly connected through Wanda and Vision’s twin boys Billy and Tommy. In the comics, Wanda conceives the twins through magic, but later discovers they were fabricated from pieces of Mephisto’s soul. When Mephisto reclaims them, Agatha erases Wanda’s memory of the twins with a spell to save her from grief. Since WandaVision is also rife with Mephisto references, from Dottie’s (Emma Caulfield Ford) line “the devil’s in the details” to the multiple 666s hidden in certain scenes, Mephisto is certainly the frontrunner for a second potential WandaVision villain. When Wanda discovers Agatha’s underground magic lair, however, the depiction of Agatha’s own magic suggests that she has a different accomplice: the Doctor Strange villain, Dormammu.
In “Breaking the Fourth Wall,” Agatha’s magic resembles Dormammu’s supernatural powers featured at the end of Doctor Strange. When Stephen Strange (Benedict Cumberbatch) confronts Dormammu, his eyes, as well as the energy that he fires from his mouth, are both a light purple hue. Similarly, when Agatha reveals her true identity to Wanda, her eyes also glow the same shade of purple. During her theme song “Agatha All Along,” purple also becomes her own signature color to represent her magic. While the similar color used to depict Agatha and Dormammu’s powers may be coincidental, magic within the MCU is often differentiated by color. Wanda’s telekinetic magic is a signature scarlet while the metaphysical spells conjured by the Masters of the Mystic Arts is typically orange. With this in mind, the purple tint to Agatha’s magic is likely intentional and insinuates that Agatha draws her magic from Dormammu’s Dark Dimension.
The unidentified magic book residing in Agatha’s lair may also provide further proof of Agatha’s connection to Dormammu. While there are several magic books from the original Marvel Comics that are possibilities, including the Necronomicon or the Tome of Zhered-Na, one theory suggests that WandaVision’s magic book is actually the Darkhold, a book on dark magic previously featured on the MCU-related TV series Agents of SHIELD. Within Agents of SHIELD, it’s established the Darkhold contains infinite knowledge and that it was made from dark matter that originated in the Dark Dimension. When the scientist Joseph Bauer (Kerr Smith) used the Darkhold to create a Quantum Particle Generator to produce new matter, the machine was actually drawing energy from the Dark Dimension. If Agatha’s magic book is the Darkhold, Agatha may be using the book to channel energy into her magic from Dormammu’s Dark Dimension.
One flaw with this WandaVision theory is the fact that Agatha is missing some of the physical features that hint when sorcerers draw power from the Dark Dimension, including a symbol on their forehead or the dark purple circles that form around the Zealots’ eyes within Doctor Strange. Since Agatha is likely drawing energy from Dormammu’s dimension to increase the power of her magic to either create the Hex herself or manipulate Wanda to do so, she wouldn’t have the purple circles around her eyes because, unlike Kaecilius (Mads Mikkelsen) and his Zealots, Agatha’s not invoking Dormammu to come claim Earth. Agatha, therefore, has more in common with the Ancient One (Tilda Swinton), who only drew power from the Dark Dimension to keep her youth. With this in mind, Agatha should have the same symbol on her forehead, but considering that the Hex warps their reality into a sitcom, it’s possible the audience hasn’t yet seen Agatha in her true form.