The Doomsday theories machine has gone into overdrive since trailer 2 and the D23 showcase, and the newest batch is the most interesting yet, because two of the biggest ones are built on the exact same four seconds of footage and reach opposite conclusions.
Here are the six that are actually circulating, ranked from most to least plausible, with what the evidence really supports. Everything below is fan speculation and rumor; Marvel has confirmed none of it.
1. Doom arrives as a saviour, then turns
The most plausible of the current Doomsday theories, because it is the only one with physical evidence.
The second Doom costume displayed at D23 is plainer and less ornate than the armored regalia from the trailers, and it closely matches the outfit from the Fantastic Four: First Steps post-credits scene. Two suits implies an arc: fans read the plain one as early-film Doom, presenting himself as the multiverse’s protector, with the ornate armor arriving after the mask slips.
It fits how the character works. Doom does not think he is a villain, and a first act where he is halfway convincing about it is the most interesting version of this film. This is the theory we would put actual money on.
2. Doom is time-slipping
The one your group chat is arguing about this week. In trailer 2, Doom is blasted out of a building and hits the ground wearing a different costume than the shot before.
The theory: the black energy swirling around him during the fall looks strikingly like the visual effect the Loki series used for time-slipping. Add the long-running rumor that Doom steals Loki’s powers on the road to Secret Wars, and the reported Loki reshoots we covered in our script leak breakdown, and you get a Doom who is not changing clothes mid-air but slipping between moments in time.
Of all the new Doomsday theories, this one explains the most footage with the fewest assumptions, and it would hand Doom a power set no MCU villain has had.
3. The X-Men destroy Tobey Maguire’s universe
The loudest one on Instagram, where a fan animation of it has millions of views, and it is all over Reddit by way of every aggregator covering it.
The claim: the film opens with the legacy X-Men triggering or exploiting an incursion that destroys the Raimi Spider-Man universe to save their own. Heroes doing something unforgivable for survivable reasons, before Doom has done anything at all.
It matches the incursion logic the MCU has been building since Multiverse of Madness, and it would explain why the legacy X-Men are in this film as participants rather than cameos. No leak, set report or insider has actually described this scene, and it appears nowhere in the leaks we have tracked since June. Treat it as fan fiction with excellent production values until someone credible says otherwise.
4. Shuri discovers the incursions
A quieter claim from insider chatter rather than fan deduction: Shuri detects anomalies in the fabric of reality, investigates, and realises universes are colliding, making Wakanda the film’s early-warning system.
Single-source, unverifiable, but structurally sensible. The film needs someone scientific to explain incursions to the audience, and Shuri is the most qualified character standing. It would also hand Wakanda a live thread to carry into Black Panther 3. This is the kind of connective-tissue detail that leaks tend to get right even when the big claims are wrong.
5. Loki saves Thor
Pure speculation, and the most emotionally loaded of the current crop. If Thor falls in this film, does the God of Stories step in?
The counterargument comes from inside the theory itself: Loki now watches over every timeline and knows billions of Thors. Why would this one be special? The answer, of course, is that it is the one the audience knows, and the one his brother was. With Tom Hiddleston confirmed for the film and his role reportedly rewritten in reshoots, something is happening with Loki; our standing Loki theories breakdown covers the older candidates. Whether it is rescue duty is anyone’s guess.
6. There are two Dooms, and RDJ’s dies
The wildest of the current Doomsday theories. Some fans are convinced the eyes behind the mask in certain shots are not Robert Downey Jr.’s, and that the costume discontinuity means two Dooms: Downey’s secretly heroic one, and a “real” villain Doom who kills him mid-film. The fan-casting for the second Doom has settled, with zero evidence, on Cillian Murphy.
The problems: side-by-side comparisons show Downey’s mole in the mask close-ups, the costume swap is better explained by theory number 2, and a decoy Doom would undercut the entire point of casting Downey in the first place. It would also be the most expensive bait-and-switch in film history. File under entertaining, not likely.
What the Doomsday theories agree on
Strip the six down and a consensus picture emerges: Doom presented as something other than a straight villain, incursions as the engine of the plot, the legacy X-Men doing real work, and Loki mattering more than his screen time suggests. That picture may be entirely wrong, but it is remarkably consistent for a film with no published plot.
For what is actually confirmed, our Doomsday release date and runtime breakdown has the short list. The older standing mysteries have their own deep dives: why Doom has Tony Stark’s face, the painting and Earth-828, where Scarlet Witch fits, and the Peggy Carter theory, which is still the best of them.
December 18 answers everything. Until then, the same four seconds of trailer will keep powering opposite conclusions, which is exactly how Marvel likes it.
Which of the six do you buy? We are on saviour-then-turn, with time-slipping a close second. Comments are open.
Sources: ComicBook, ComicBook (D23 suit), SlashFilm, plus theories circulating on X, Reddit and Instagram, credited where identifiable. Every theory above is unconfirmed fan speculation; Marvel Studios has verified none of it. Avengers: Doomsday is a Marvel Studios production; all rights belong to Marvel Studios and Disney.
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