The creator talks about the name of Mephisto in “Agatha All Along”

Warning: This article contains spoilers from Agatha – All the time Episode 3: “Through many miles of tricks and trials.”

As far as the Agatha – All the time According to theories, two characters quickly rose to the ranks of major guesses for a surprise reveal down the road: Wanda Maximoff herself (Elizabeth Olsen) or Mephisto, an all-powerful demon with ties to Agatha Harkness in the Marvel comics. Whether either will appear is still unclear, but the clues are there, and Episode 3 now points more clearly to the latter possibility.

The first trial on Witch Street presents Agatha Harkness (Kathryn Hahn) and her coven with a seaside home that magically grants them East Coast-style wasp costumes—high pinstripe shirt collars, pearls, and wine for all. As they survey the scene, potions expert Jennifer Kale (Sasheer Zamata) has a one-on-one moment with the mysterious teen (Joe Locke). Still unable to share details about himself with the other witches due to a seal placed on him by an as-yet-unknown entity, Jennifer considers all the possibilities of his true identity—much as viewers do themselves.

One possibility she considers is that this teenager could be “an agent of Mephisto.” In an interview with Weekly entertainment which took place before the show's premiere on Disney+, showrunner Jac Schaeffer addresses this particular namedrop in Episode 3, titled “Through Many Miles of Tricks and Trials,” which is sure to raise eyebrows among comic book fans.

“So often on these shows there's something that's simultaneously a joke and a wink and a nod and actually has something authentic about it,” Schaeffer comments. “As we all know, Mephisto is a character that's very much tied into Agatha's storyline. I mean, people have to watch, but we're always playing with the audience in that way.”

Mephisto is a fun game because fans of WandaVision When it aired, it was theorized that the character was somehow involved. However, this hypothesis was proven false. Inspired by the demon Mephistopheles, Mephisto rules over a dimension in the underworld and is determined to acquire as many souls of the living as possible. He often appears in the guise of the biblical Satan and loves a good, mischievous deal or trick to get what he wants.

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A current fan theory that is gaining popularity online for Agatha – All the time is that Aubrey Plaza's Rio Vidal, the so-called “green witch” who has a backstory with the main character, could actually be an interpretation of Blackheart, a child of Mephisto from the comics. Rio mentions in the first episode that she has a black heart that beats for Agatha, while Patti LuPone's fortune-telling witch Lilia Calderu draws a black heart when she foresees another witch joining her coven. Or could Rio be Mephisto himself in disguise?

“I can't say everything about my character right now, but I will say there are all kinds of facets to her,” Plaza previously revealed to EW about Rio. “I really wanted to try and bring in a kind of chaotic energy and spontaneity that keeps Agatha on her toes, and just have fun playing in that dynamic.”

As for the other big theory, whether Olsen himself is in Agatha – All the timeSchaeffer talks about how much of Wanda's shadow she wanted to include in the series.

“There was a lot of thought,” she says. “That's a great way of putting it: her shadow. Agatha is not a character who is in anyone's shadow. So this is very much Agatha Harkness' show. But we are in the WandaVision corner of the universe, so Wanda's legacy is included in that narrative. But yes, it's about Agatha. It's about her journey, it's about the truth about her, and that's something we're very focused on in the show.”