The central antagonist of Ironheart, Parker Robbins/The Hood, pushes the MCU into the dark mystical world. While the Doctor Strange movies hinted at darker dimensions, it is Ironheart's Hood that may finally bring in the literal figure of all evil in the Marvel Cinematic Universe, Mephisto. Fans believe that Sacha Baron Cohen may appear in one of the final three episodes next week.
However, it is important to note that Mephisto's role in the six-episode miniseries Ironheart has not been officially confirmed as of now. However, given the mysterious demonic entity in the closing minutes of the third episode, it is most possibly Mephisto, who in the comics is known to possess shape-shifting abilities.
Was that Mephisto in Ironheart Episode 3?

Parker Robbins/The Hood loses his cousin John in Ironheart, Episode 3, "We in Danger, Girl". A distraught Parker is about to quit the demonic entity, but that's when he is shown how John died. He learns that Riri left John to suffocate and die in the room. After showing the vision, the silhouette of the demonic entity transforms into Riri's armor, informing him who is responsible for John's death.
While the episode does not confirm the identity of this mysterious entity, it is probably the Marvel Universe's devil, i.e., Mephisto, who is known for possessing shape-shifting powers in the comics. But, chances are slim that Mephisto will be confirmed before the final three episodes of Ironheart are released. Furthermore, introducing Mephisto is not the only way the series is pushing the MCU.
The miniseries sets up Doctor Doom in a big way:
We know that the main villain of the MCU's Multiverse Saga in the upcoming Avengers: Doomsday and Avengers: Secret Wars is Victor Von Doom, or Doctor Doom, played by Robert Downey Jr. In the Marvel lore, Doctor Doom is known for his proficiency in utilizing both magic and science and combining them. However, this miniseries will be the first in the MCU to show that magic and science can be combined.
Ryan Coogler, who is an executive producer in the series, confirmed this to Deadline at the red-carpet premiere of the series:
"It's so crazy to be putting this movie out now, at a time where AI is on everybody's mind [...] when the MCU's gearing up, and we didn't know it was going to be Doctor Doom and the Avengers, in a different story. But he's the guy, in publishing, who's most famous for fusing technology and magic, so it's a great sample of things that are coming. It's probably going to be the biggest movie in Marvel history."
For those who don't know, one of the trailers for the show revealed that Riri builds an armor that's powered by magic. Therefore, given how Parker Robbins is on her tail for killing his cousin, Riri will be pushed to expand her world view to counter his dark magic.
Are you excited for the final three episodes of Ironheart? In case you are interested, the first three episodes are accessible on Disney+.