Marvel fans have spent the last year throwing thousands of theories at the wall. Some sound like pure fan fiction. Others are built around confirmed casting decisions, established comic storylines, and details Marvel has publicly revealed.
With Avengers: Doomsday positioned as one of the central films of the Multiverse Saga, speculation has become increasingly focused on what the movie might do before Avengers: Secret Wars arrives.
The confirmed pieces are already significant. Robert Downey Jr. is returning to the MCU as Doctor Doom, the Russo Brothers are directing, and Marvel has announced major legacy X-Men actors alongside the Fantastic Four and returning Avengers characters. Those details establish the scale of the project, but they do not confirm the film’s ending or its full plot.
The theories below are therefore divided between what Marvel has established, what comes from comic-book precedent, and what remains speculation.
Confirmed: Doctor Doom Is Not Officially Tony Stark
One of the earliest theories suggested that Robert Downey Jr.’s Doctor Doom would simply be an evil Tony Stark variant from another universe.
Marvel has not supported that interpretation. The studio has announced Downey as Victor von Doom, not as an alternate version of Tony Stark. Unless Marvel later reveals a connection between the two characters, Doom should be treated as a separate figure.
That distinction matters because Victor von Doom is one of Marvel’s most important villains in his own right. He is a monarch, scientist, sorcerer, strategist, and political leader whose rivalry with Reed Richards stretches across decades of comic-book stories.
Turning him into “evil Iron Man” would be an unnecessarily narrow use of the character.
The more convincing explanation for Downey’s casting is thematic rather than literal. Marvel is using the face most associated with the MCU’s original era to introduce a threat to its future. Audiences do not need years of history with Doom to understand the shock of seeing Downey become the person standing against the heroes.
That is an interpretation of the casting, not a confirmed plot detail.
Confirmed: Secret Wars Follows Doomsday
Marvel has officially announced Avengers: Secret Wars as the follow-up to Avengers: Doomsday. That has led to one of the most persistent theories surrounding the two films: Doomsday may adapt elements of Jonathan Hickman’s Secret Wars storyline before the larger event is completed in the next movie.
In the comics, multiversal incursions threaten to destroy entire realities. Doctor Doom eventually exploits the collapse and reshapes existence into Battleworld, placing himself at the center of a new order.
Marvel has not confirmed that the films will follow that exact structure. It has, however, established a multiversal story involving the Avengers, Fantastic Four, and X-Men, making comparisons to Hickman’s material understandable.
The most plausible prediction is that Doomsday could function as the MCU’s major collapse movie, while Secret Wars deals with the consequences. That would resemble the structure of Infinity War and Endgame, although Marvel has not officially described the films in those terms.
Not Confirmed: Anthony Mackie Did Not Confirm A Cliffhanger Ending
The previous version of this article claimed that Anthony Mackie had confirmed Doomsday would end on a cliffhanger. That claim should be removed.
No verified interview, date, or outlet has been identified to support the statement. There is therefore no basis for attributing that specific information to Mackie.
A cliffhanger remains a reasonable fan prediction because Secret Wars follows Doomsday and the comic storyline involves Doom gaining enormous power. But it is still a theory, not something confirmed by Mackie or Marvel.
Not Confirmed: The Avengers And X-Men May Fight Before Joining Forces
The idea of the Avengers and X-Men initially fighting each other has circulated for months. Unlike some leak-based theories, it has a clear foundation in Marvel’s comic history.
The two groups have often disagreed over mutant rights, government control, political responsibility, and the use of power. In a story involving collapsing universes, both teams could easily suspect that the other side is responsible for the crisis.
Marvel has confirmed the presence of major X-Men characters alongside Avengers and Fantastic Four members. That makes a confrontation possible, but it does not confirm that the teams will actually fight.
There is also no verified production report establishing a specific Avengers-versus-X-Men battle. The idea should remain in the speculation category until Marvel releases footage or story information that supports it.
A temporary conflict would make narrative sense, particularly if the heroes come from different realities and do not initially understand what is happening. The likely fan expectation is that the disagreement would eventually give way to a larger alliance against Doom.
Confirmed Rivalry: Reed Richards Could Be Doom’s Main Opponent
Reed Richards is one of the strongest candidates to become Doctor Doom’s primary rival.
Marvel has officially integrated the Fantastic Four into the film’s cast, and the relationship between Reed and Doom is one of the most established rivalries in the comics. Their conflict is not based only on physical strength. It involves intelligence, ego, resentment, scientific achievement, and competing ideas about how the world should be governed.
That makes Reed a more natural counterweight to Doom than simply giving the villain another powerful opponent to fight.
The film has not confirmed that Reed will serve as its central hero or that he will personally defeat Doom. But if Marvel wants to explain why Doom is dangerous beyond his armor and magical abilities, Reed is the character best equipped to challenge him intellectually and emotionally.
Not Confirmed: Thor Could Have A Major Role
Thor is another character frequently mentioned in theories about the film’s central heroes.
He remains one of the few surviving members of the original Avengers lineup, and his history gives him a natural connection to cosmic-scale threats. He also has the experience, power, and emotional history needed to anchor a story involving multiple universes.
However, the claim that Marvel is positioning Thor as the film’s secondary lead has not been confirmed by a named Marvel source. There is no verified evidence that he has a larger role than Sam Wilson, Reed Richards, Doctor Strange, or any other major character.
Some fan discussions have also connected Thor’s potential storyline to Love, his adopted daughter. That possibility comes from the character’s established MCU history, not from confirmed Doomsday plot information.
Until Marvel releases more footage or official story details, Thor’s exact role remains unknown.
Not Confirmed: Doctor Doom Could Win
Doctor Doom winning the first major confrontation is one of the more convincing theories because it fits the larger structure of the Multiverse Saga.
If Secret Wars follows Doomsday, Marvel may want the first film to end with the heroes facing a defeat rather than celebrating a complete victory. The comic version of Secret Wars also gives Doom a near-godlike position before the heroes challenge his control over Battleworld.
That does not prove the MCU will follow the same path. Marvel has changed major comic events before, and the studio has not confirmed that Doom will rule Battleworld, defeat the Avengers, or reshape reality at the end of Doomsday.
The title itself is not evidence of a defeat either. Doomsday could refer to the threat facing the universe rather than the outcome of the battle.
Still, a darker ending would give Secret Wars a stronger starting point. If the heroes win too cleanly in Doomsday, the next film would have less room to establish the scale of its crisis.
What The Most Plausible Theories Have In Common
The strongest Avengers: Doomsday theories are the ones built around details Marvel has already confirmed or storylines that naturally connect to the film’s premise.
Doctor Doom is a separate character from Tony Stark.
The Fantastic Four give Doom a personal and intellectual rival in Reed Richards.
The X-Men’s presence creates the possibility of conflict between different superhero groups.
Thor has the history and power to play a major role, although his exact importance remains unknown.
And Doom potentially winning the first major confrontation would fit the structure of a story leading into Secret Wars, even though no such ending has been confirmed.
For now, Marvel has revealed enough to make those predictions credible without confirming the details fans most want to know. The film’s scale is established. Its final outcome is not.
That distinction is important, especially with Avengers: Doomsday. The closer the movie gets to release, the more theories will be presented as certainty. Until Marvel confirms them, Doctor Doom’s victory, a cliffhanger ending, an Avengers-versus-X-Men battle, and Thor’s exact role should all remain theories rather than facts.
Sujal Singh is the Founder and Editor of CineMazze. He covers film news and updates, including casting, production and release announcements, and manages the website. Follow him on Instagram: @itssujalsingh.
