For weeks now, WandaVision has been dropping clues and references to Mephisto, Marvel's devil, hinting that he might be the real villain pulling all the strings. But given that the story had heavily stressed at Wanda being the antagonist as well, only to reveal that she is being manipulated by Agnes a.k.a. Agatha, we are having a hard time agreeing that all the hints about Mephisto are not just there to distract us from the bigger picture- Agatha is using Wanda to allow an ancient villain, an eldritch monster to be precise, to set foot on Earth, i.e., Chthon, one of the Elder Gods who turned into demons. Spoilers ahead

Before we go on to explain our theory in-depth, let us tell you another crucial point:

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Why we think Agatha isn't working alone?

Well, for starters there is the ever-consistent gut feeling which just didn't find Agatha at par with the mighty villains MCU has churned in the past. There is also the fact that the quirky "It was Agatha all along" song only revealed how Agatha fits into an already established plot, how she has been manipulating Wanda's surrounding, and as we mentioned earlier, trying to make her expend a large quantity of her power to weaken her. She looks less like the true villain and more like the lackey of one who is setting the stage for them. 

And despite how Agatha's spooky dungeon literally screamed "Mephisto" with all those devilish figurines and signs, it is the mysterious book (which we think is the Darkhold), radiating evil energy that says otherwise. And if we are right and it's indeed the Darkhold, the ancient book of dark spells that can bring nothing but chaos, then we might be dealing with a different, more powerful kind of evil whose presence WandaVision is teasing just like Thanos' arrival was hinted at since The Avengers

Chthon was one of the first Elder Gods, often known as the God of Chaos for his practice of dark, chaotic magic. Over the years, he turned into a power-hungry demon who fled into his own dimension to escape the God-Eater set lose on him by the goddess, Gaea. 

What's the Darkhold?

In the comics, The Darkhold, also known as the "The Shiatra Book of the Damned" or "The Book of Sins," was penned and put together by the Elder God Chthon who left behind these evil, imperishable scrolls on Earth in order to channel his power and presence through them. The Darkhold can be read by anybody as it automatically changes itself to be in the native language of the reader. But the spells held within its pages have the ability to corrupt anyone, such that they are open to Chthon's manipulation, even though he is trapped in a whole other dimension. 

One of the many spells hidden within the book allows one to control the will of others. Chances are that Agatha Harkness read the book, got influenced by the mighty Chthon, and used the book to control Wanda's will. This allowed her to use Wanda to create the fake reality within Westview and make it seem like it was all Wanda's doing, without the Avenger realizing the destruction and pain she is causing in the process. 

We have already seen The Darkhold in two of Marvel's TV shows- Agents of S.H.I.E.L.D. and the rarely remembered, Runaways. It played a significant role in the former where we saw how the book was used to create the evil Framework in which the team was lost in season four, left to figure their way out of an alternate reality controlled by HYDRA. As per the appearance of the dark grimoire in the shows, it was made explicit that the book possesses the power to bring the reader's desires to come true but, in the process, the person's mind is corrupted by its contents and they develop a dangerous obsession to possess the Darkhold, such that they are ready to kill to become its sole owner. 

We agree that if the book in Agatha's basement is indeed the Darkhold, it is starkly different from how it looked in the TV shows. But the book is known to reform itself and change its appearance when damaged, maybe that's what happened here too. Or maybe, the above-mentioned shows are still not canon and WandaVision is presenting its own version of the Darkhold. 

Now, back to the big questions:

How do Wanda and Westview fit into the picture here?

Since the beginning, one of the lesser asked but still crucial questions was why was Westview chosen for Wanda's dream world. Well, the latest advertisement in the series might have just answered the question- the "Nexus" antidepressant. For Marvel comics readers, who obviously jumped in excitement on seeing the name, know that the word "Nexus" holds two meanings- the "Nexus of All Realties" and a "Nexus being." And we believe that the advertisement is referring to both. 

Let's start with the "Nexus of All Realities." It is like a focal point of sorts, described as a cross-dimensional getaway in the comics, where the alternate universes, all possible realities, and realities between realities naturally intersect, allowing someone to travel between two universes. Though in the comics, it is located in the Florida Everglades, maybe in WandaVision it exists in Westview, in Agatha Harkness' gloomy and dark dungeon-like basement. This would explain why the small town was chosen by Agatha in the first place. She somehow lured an aghast and broken Wanda to the town, used the book to control her will, ultimately to break Chthon free from his dimension and bring him into this world. 

But why Wanda?

As we mentioned, we believe that the ad in "Breaking the Fourth Wall" was also referring to the existence of Nexus beings who have been described in the comic books as "rare individual entities with the power to affect probabilities --- and thus the future." And one such being is Wanda, "a living focal point for earth's mystical energies" and the core of the Multiverse. Once Elizabeth Olsen herself noted that her character "is the only human being from this universe who can communicate with paranormal things and the past and the future and other universes."

Chances are that the advertisement is also referring to both Wanda and Chthon. The advertisement goes as follows: "Ask your doctor about Nexus. A unique anti-depressant that works to anchor you back to your reality. Or the reality of your choice. Nexus, because the world doesn't revolve around you. Or does it?"

For Wanda, the "Nexus" is the "Nexus of All Realties" that she unknowingly chose to get the reality of her choice- one where she is living her happily-ever-after with a very much alive Vision. And for Chthon, the "Nexus" is Wanda as Earth's Nexus being whose powers will allow him to get to the reality he wants to be in i.e., the Earth in the MCU. 

There are other reasons that make Wanda the perfect candidate

You see, Chthon needs two things to break free from his dimension- the Darkhold which allows him to travel easily through dimensions and the use of a massive amount of magical powers that would create a mystical rift through which he can enter Earth. And what place better than the Nexus of All Realities to open it?

Mephisto (quit rolling your eyes) could still be in the picture, but more like a passive entity. Maybe when fake Pietro called them "demon spawn," he wasn't kidding- Agatha could have created the twins by harnessing Mephisto's essence by some spell in the Darkhold. 

Our bet is that Agatha is either going to use Wanda's kids as leverage (or maybe something worse is in order if they are indeed fragments of Mephisto's soul) to make the Avenger lose control and unleash her massive powers (just like it happened in the House of M) to open up the rift, inadvertently creating the very thing needed to bring Chthon to Earth. 

As for the aftermath, in the comics, Chthon had marked Wanda when she was a child as his intended vessel and possessed Wanda more than once to wreak havoc. Maybe that's also a reason Agatha manipulated Wanda to get her where she is today. Who is to say that Chthon won't be possessing Wanda to gain corporeal form once he is on Earth? 

For all those who are still on the "It's Mephisto" ship- it could still be Mephisto. WandaVision had been dropping obvious hints about Agnes' now confirmed true identity long before she lured Wanda to her secret lair. Maybe the heavy references to Marvel's devil are right on the money too. Catch the latest episode of WandaVision currently streaming on the official Disney+ app.