Kevin Feige and the people involved in the Marvel Cinematic Universe are usually better at keeping secrets about stuff like this. However, ever since the Agatha All Along series was announced, there have been whispers and rumors that a certain "big bad" would be introduced to the MCU once and for all. While the imposing villain hasn't made an appearance yet, it seems extremely likely that he will before the Disney+ series closes out its season. Even if an appearance is reserved for some other movie or television show, audiences know now that he does indeed exist in the same world as Agatha, Wanda, Doctor Strange and the rest.

Agatha All Along Episode 3 Confirms Mephisto's Existence

Almost from the first episode of Agatha All Along, it seemed like the show desperately wanted to divulge that Mephisto played a part in this universe. However, the writers bit their collective virtual tongues until Agatha and the rest of her ragtag coven started down The Witches Road. Along this path to glory and power the group encountered a luxury beach house that contained their first real trial.

As the witches worked their way through and then out again, the members of the coven began to get to know each other better. An essential conversation between Jennifer Kale and the still mysterious Teen shed a bit more light on one aspect of Agatha's potential backstory. Jennifer told the teen there are rumors that to increase her power, Agatha exchanged her baby for the Darkhold and her son, Nicholas Scratch, is possibly now a demon or Agent of Mephisto.

Agatha exchanged her baby for the Darkhold and her son, Nicholas Scratch, is possibly now a demon or Agent of Mephisto.

This conversation isn't only important because it confirms once and for all that Mephisto exists in the MCU, even if he could still be more of a legend than a true, living entity. But because it delivers a massive hint at who put the whammy on Teen so that he can't tell anyone who he is, as well as what exactly his real identity might be. Teen's reaction to what Jennifer told him seems to hint he knows more about Mephisto and Nicholas Scratch than he let on.

Mephisto Long Hinted At But Never Confirmed

In a cinematic universe that has already confirmed magic not only exists but is quite prevalent among certain practitioners, as well as a universe that has shown off hell-dimensional beings like Dormammu, fans of the MCU had long believed it was only a matter of time before Mephisto was confirmed. There was some surprise he wasn't talked about more in Doctor Strange: Multiverse of Madness as the Darkhold and dark magic were thrown around pretty liberally.

Outside of Agatha All Along, there have already been whispers and rumors that Mephisto will make an appearance soon. One film he's been talked about the most is Ironheart, which focuses on the Riri Williams character first introduced in Black Panther: Wakanda Forever. However, it never made much sense for Ironheart to be the first movie where Mephisto is mentioned. It could, however, be the first movie where he's seen.

Could Mephisto Appear In Agatha All Along?

Now that Mephisto has been officially confirmed as part of the MCU the only question left is whether or not he'll make an official appearance in Agatha All Along or whether he might simply be talked about. Other rumors surrounding the show have centered on Aubrey Plaza's character and believe she might be an agent of Mephisto. If that is the case, the Disney+ series could handle the demon much in the same fashion the MCU handled Thanos before him.

Instead of really showing too much or even having him be a part of the action in any way, Mephisto could work through his agents (of which Teen could be one) and simply be an imposing presence just off-screen.

The showrunner has confirmed Mephisto will appear at some point, just not when.

This theory would then lead to Agatha and Mephisto both showing up in Ironheart, with that film being the first time he's fully officially shown off. There is also a chance that Mephisto could make an appearance without the other characters in Agatha All Along even knowing it. Someone with his powers might have already appeared in the form of someone else and rather than being an agent, he could be interacting with the coven directly.