Mephisto has yet to show up in the MCU, but the franchise has hinted at the character many times throughout its 29 movies and eight Disney+ shows. While the devilish villain has been most frequently teased in MCU Phase 4, Mephisto's origins as a Marvel Easter egg actually go back to Phase 1. And with credible rumors about Mephisto's casting now making the rounds, the payoff to all these clues seems to be closer than ever.
In the comics, Mephisto is essentially Marvel's version of Satan, having all the abilities typically associated with the Devil, such as immortality, superhuman strength, manipulation, and all sorts of magical powers. Mephisto has been an adversary to nearly every Marvel superhero at one point or another, playing key roles in the comic versions of Avengers: Secret Wars. While the character hasn't been confirmed to exist in the MCU, Mephisto's presence has always been known, with various Easter eggs and references setting up Marvel's Prince of Darkness. So, here is every time the MCU has hinted at Mephisto.
The Tesseract File In The Avengers
Mephisto's first reference in the MCU goes back to The Avengers heavily revolves around the Tesseract, a powerful cosmic cube that is later revealed to contain the Space Stone. At one point in the movie, a shot of a S.H.I.E.L.D. file on the Tesseract can be seen, and Mephisto's name appears clearly in a description under an image of the object. However, the formatting of the page makes it impossible to see the context of the reference, and a character's hand is covering parts of the text. While this setup is small, it shows that Mephisto has been on S.H.I.E.L.D.'s radar since the very beginning, meaning that whenever he finally shows up, they will be ready.
All The Devil Imagery In WandaVision
While Mephisto doesn't end up appearing in WandaVision contains all kinds of references to Mephisto, with the most apparent being the show's excessive amount of Devil imagery. References to "666," a number closely associated with Satan in Christianity, can be seen several times throughout the show, including on a toaster in episode 1. The Hex that Wanda contains Westview in is even six-sided, furthering this theme.
WandaVision also has several references to demons from literature. Westview's theater is called the Coronet Theater, named after an Andrew Marvell poem that tells the story of a man attempting to make a crown for Christ, only for him to run into the Biblical serpent among some flowers. Another literary reference comes in the form of Agatha Harkness's rabbit, Señor Scratchy, a reference to Old Scratch, the nickname for the Devil popularized by Washington Irving's 1824 short story "The Devil and Tom Walker." Finally, several lines in WandaVision reference Mephisto, including when Dottie says "the devil’s in the details" in episode 2, and when Quicksilver calls Wanda's children "demon spawn" in episode 6. However, that final reference goes a little deeper than the rest.
Wanda's Pregnancy In WandaVision
In WandaVision, Wanda becomes pregnant and has two children: Billy and Tommy Maximoff, also known as the superheroes Wiccan and Speed. However, the twins are all part of the Hex's illusion, with them magically being created by Wanda. While the twins' birth is mostly explained by magic, there is a lot of room for expansion on the two character's origins. Billy and Tommy are real on Earth-838 without the Hex, meaning that something else has to be involved — that's where Mephisto comes in. In the comics, Billy and Tommy are created when Wanda borrows Mephisto's life essence in order to give the twins souls. However, Mephisto eventually takes the kids back, leading to a story involving Wanda coping with the loss of her children.
While the first part of this story has been told, there is still room for Mephisto to enter the MCU and reveal that he had a hand in creating Billy and Tommy, filling in the gaps of their vague MCU origins. This idea was a popular theory for a while, but it has since been disregarded as it didn't happen in WandaVision. However, as Mephisto fan theories positing that Wanda could eventually turn to Mephisto in order to get her kids back. Although Mephisto hasn't been confirmed to be involved in Wanda's pregnancy, WandaVision leaves the possibility of his involvement with Billy and Tommy open.
The Stained Glass Window In Loki
Loki season 1 hints at Mephisto through some more Devil imagery, this time in 16th-century . In episode 2, the Time Variance Authority visits a classical French church that features a stained-glass window with a clear image of the Devil. This reference ended up baiting fans into believing Mephisto would make an appearance in Loki since the window actually hints at how Sylvie and Loki would bring chaos to the multiverse. However, the window's image of a horned, red-skinned monster looks nothing like Loki or Sylvie — yet it looks exactly like Mephisto.
The origin of Loki's devil window is never explained, but the aesthetic of the image has to be based on something. It could be that Loki is hinting that Mephisto has existed in the MCU for a long time, with the various demon stories in different religions taking inspiration from the villain. If this is the case, it's entirely possible that the religious people from that time period simply mixed up the tales of Loki and Mephisto, as combining aspects from various folklore and religious tales is not an uncommon thing.
Jake The Goat In She-Hulk
The MCU's final Mephisto hint, so far, appears in She-Hulk: Attorney at Law Easter egg could be more than just a reference, as the true identity of this goat demon stays unresolved by the end of the series.
Goats are an animal commonly associated with the Devil, and while a demon named Jake doesn't exist in Marvel Comics, there is one named Jack — and that demon is Mephisto. Jack Scratch is one of Mephisto's many aliases, and it is possible that Madisynn simply misheard "Jack" as "Jake" considering her drunken state and the overwhelming environment of Hell. Mephisto was confirmed to exist in the MCU all the way back in The Avengers, and now She-Hulk: Attorney at Law has a character who has possibly met Mephisto, hinting that the villain's MCU debut could be closer than ever.
