The Fantastic Four: First Steps takes place in a parallel reality and revolves around a version of Marvel's First Family that hails from a retro-futuristic New York City inspired by the 1960s.
The team will be front and centre in Avengers: Doomsday, and the expectation is that they'll become a permanent part of the new Marvel Cinematic Universe post-Avengers: Secret Wars. There's always a chance they'll remain in their own reality, but that potentially closes the door on a lot of very exciting team-ups.
While the Fantastic Four will battle Doctor Doom in the next Avengers movies, there's been no official word on whether Robert Downey Jr.'s Variant hails from their world or even if they've crossed paths with Victor during the four years since gaining their powers.
Avengers: Doomsday being the first time Reed Richards and Doom meet would wipe away a lot of comic book history, though it's always possible that Victor simply hates every version of the Fantastic Four across the Multiverse.
While we still don't have a definitive answer about when or where Doom comes from, scooper @MyTimeToShineH has learned, "There's a scene in [The Fantastic Four: First Steps] where the major world leaders are together discussing the threat of Galactus - and there’s an empty spot with a flag that says Latveria!"
If Latveria does indeed exist in this reality, then it stands to reason that Doom does, as well. Perhaps Downey's Variant knew Reed in college, but was scarred while trying to find another living Variant of his mother (in the comics, he tries to rescue her from Hell). If he was then lost in the Multiverse, he may not have seen Pedro Pascal's Reed since.
On the other hand, it makes just as much sense for Doom to not hail from the same reality as the Fantastic Four, especially taking into account what we know of his appearance and plans for the Multiverse (if previous rumours are accurate, the villain's home has already been destroyed).
Still, Avengers: Doomsday being where Mister Fantastic and Doctor Doom battle for the first time is a little disappointing. Marvel Studios could have done with maybe one more movie featuring the team to establish Doom before he takes centre stage in the two-part Multiverse Saga finale, but it wasn't meant to be.
Plus, with Doom being a last-minute pivot from Kang the Conqueror, though, that was always going to be wishful thinking.
The Fantastic Four: First Steps is set to be released in theaters on July 25, 2025.