Avengers: Doomsday Explained Before You Watch: Doctor Doom, the Multiverse and What to Watch First

12 Nov

Three glowing spheres, each containing a different city or world, colliding in dark space as cracks of emerald-green lightning bind them together. — Marvel says Avengers: Doomsday sees three universes on a collision course. Conceptual scene, not a still from the film.

Robert Downey Jr. Is Back, and This Time He Wears the Mask

Avengers: Doomsday is the first Avengers film since Endgame in 2019, and Marvel has spent more than a year building towards it with post-credits scenes, a rerelease and a long official homework list. It opens in UK cinemas on Wednesday 16 December 2026, two days before its US release on Friday 18 December.

This is a before-you-watch guide, not an ending explainer. It covers what Marvel has confirmed about Doctor Doom and the story, how the multiverse has been set up so far, the scenes that point directly at Doomsday, and what is genuinely worth watching first. It does not guess at the film's plot or ending.

Spoiler note: this guide discusses the endings and post-credits scenes of earlier Marvel films and series, including Endgame Encore, The Fantastic Four: First Steps and VisionQuest. It reveals nothing from Avengers: Doomsday beyond Marvel's official material.

When Is Avengers: Doomsday Released in the UK?

Disney's UK press office lists Avengers: Doomsday as releasing "exclusively in cinemas 16th December, 2026". Disney has confirmed the Wednesday date, which moved the UK opening two days ahead of the 18 December date originally announced. In the US and on Marvel's own site, the release date is 18 December.

Opening in Britain first is not unusual for Marvel. Avengers: Endgame arrived in the UK a day before the US, and Infinity War two days before. It does mean UK audiences will see the film before most of the American internet does, and anyone hoping to avoid spoilers should plan to go early.

The film is a cinema exclusive. It will also play in Infinity Vision, Disney's new certification for premium large-format screens. No streaming date has been announced, so a Disney+ release is some way off.

Who Is Doctor Doom?

Victor von Doom was created by Stan Lee and Jack Kirby and first appeared in the fifth issue of Fantastic Four in the early 1960s. Marvel's own introduction describes him as the ruler of Latveria, a fictional European nation, and "a master of both sorcery and technology". He began as a rival to Reed Richards, Mister Fantastic, and went on to fight heroes across the Marvel universe, from Spider-Man to the Avengers. That combination of science and magic is why he is such a natural villain for a story about the multiverse: he has a foot in both of the MCU's big systems of power.

He has never appeared in the Marvel Cinematic Universe before. Doomsday is his debut, with Robert Downey Jr. in the role.

Why Robert Downey Jr.?

Downey played Tony Stark in ten Marvel films, and Tony died at the end of Endgame. His casting as Doom was revealed at San Diego Comic-Con in July 2024, in an elaborate Hall H stunt: a line of figures in green cloaks and Doom masks walked on stage, and one of them took off his mask to reveal Downey. "New mask, same task," he told the crowd.

The same panel confirmed that Joe and Anthony Russo, who directed Infinity War and Endgame, would return to direct both Avengers: Doomsday and Avengers: Secret Wars, with Stephen McFeely writing. That replaced an earlier plan. Marvel had previously announced Avengers: The Kang Dynasty as the fifth Avengers film, built around Jonathan Majors as Kang. In December 2023 a New York jury found Majors guilty of assault and harassment of a former girlfriend, and Marvel cut ties with him, which forced a rethink of the saga's main villain.

The obvious question is whether Doom has any connection to Tony Stark. Marvel has not said. Fans have long suggested Doom could be a version of Tony from another universe, and the studio has done nothing to discourage it (see the Endgame Encore section below). But that remains a theory. The film itself will answer it.

What Marvel Has Said About the Story

Marvel's official logline is short: "beloved heroes from three distinct universes will be set on a deadly collision course and face an existential threat unlike anything they've ever encountered."

Marvel's own guide to the film fills in which universes those are. The trailer released in July 2026, narrated by Downey's Doom, shows the danger facing "the Avengers, Fantastic Four, and the X-Men as their worlds collide". That means three groups of heroes from three realities: the main Marvel universe, the retro-futuristic world of The Fantastic Four: First Steps, and the world of the X-Men films made by 20th Century Fox from 2000 onwards.

That is as far as the official story goes. Who fights whom, who survives, and what Doom actually wants are things the film has to reveal.

Who Is in the Cast?

Disney's official billing lists Robert Downey Jr., Chris Evans, Chris Hemsworth, Pedro Pascal, Paul Rudd, Anthony Mackie, Florence Pugh, Vanessa Kirby, Ebon Moss-Bachrach, Wyatt Russell, Channing Tatum, Simu Liu, Ian McKellen, Tom Hiddleston, James Marsden, Patrick Stewart, Joseph Quinn, Sebastian Stan, David Harbour, Letitia Wright, Lewis Pullman, Kelsey Grammer, Kathryn Newton, Danny Ramirez, Winston Duke, Alan Cumming, Hannah John-Kamen, Rebecca Romijn and Mabel Cadena, with Tenoch Huerta Mejía.

Several points stand out. It reunites Downey, Evans and Hemsworth for the first time since Endgame. Pascal, Kirby, Quinn and Moss-Bachrach bring the Fantastic Four across from First Steps. And Stewart, McKellen, Marsden, Cumming, Romijn and Grammer are actors from the Fox X-Men films. Marvel's billing does not say which characters every actor plays, so treat any role you see attached to Evans, for example, as unconfirmed until the film is out.

The Multiverse So Far

The multiverse is the idea that there are many parallel realities, each with its own version of events. Marvel has been building it for five years.

Loki is the clearest guide. Its two seasons introduced the Time Variance Authority, an organisation that once pruned unwanted timelines to protect a single "sacred" one. At the end of the second season, Loki takes his place at the centre of the branching timelines, holding them together so they can exist at all. Spider-Man: No Way Home and Doctor Strange in the Multiverse of Madness showed what happens when those realities bleed into each other: heroes and villains from other worlds crossing over, and universes damaged as a result.

The Fantastic Four: First Steps is set entirely in another reality, designated Earth-828 in Marvel's numbering. The post-credits scene of Thunderbolts*, released earlier in 2025, showed the Fantastic Four's ship arriving in the main MCU reality. Marvel has not explained who was aboard or why.

The Scenes That Point at Doomsday

Marvel has used post-credits scenes to set up Doom more directly than any villain since Thanos. These are the ones that matter most.

The Fantastic Four: First Steps

In the film's mid-credits scene, set four years after the main story, Sue Storm leaves her young son Franklin for a moment. When she returns, a figure in a green hooded cloak is kneeling in front of him, holding a silver mask. The figure's face is never shown and he does not speak, but the music cue and the costume make it clear this is Doom. Franklin matters because the film establishes that he has extraordinary, apparently cosmic power. Why Doom wants him is not explained.

Avengers: Endgame Encore

The rerelease of Endgame, which opened in UK cinemas on 25 September 2026, added four new scenes. Not every screening included all of them: some appeared only in premium-format presentations.

The first extends the ending. Steve Rogers and Peggy Carter, dancing in their retirement, are interrupted by a knock at the door. It is Loki. The second, during the credits, finds Bruce Banner in an underground facility after Spider-Man: Brand New Day, trying to keep the Hulk contained. A voice, Doom's, says he is there to "collect" him. A third shows the TVA watching universes collide and vanish in their thousands, including the reality of the Fox X-Men films. The last reworks Endgame's closing sound of Tony Stark hammering his first suit in a cave, ending instead on Doom's mask.

Our guide to what Endgame Encore added and how it changes the ending goes through those scenes in detail. Joe Russo has described the rerelease as "required viewing for following the story in Doomsday".

VisionQuest

The latest piece of the puzzle arrived on 11 November in the UK. The finale of VisionQuest, the Disney+ series starring Paul Bettany, ends with a second post-credits scene that returns to Mount Wundagore, where Wanda Maximoff, the Scarlet Witch, brought the mountain down on herself in Doctor Strange in the Multiverse of Madness. Green magic lifts the rubble, a hooded figure identified as Doom tells her that her power will be his, and Wanda's eyes open.

Taken together, these scenes show a pattern. Doom has sought out a child with cosmic power, the Hulk and the Scarlet Witch. What he means to do with them is the business of the film.

What to Watch First

Marvel and Disney+ have published an official "Countdown to Avengers: Doomsday" collection. By one widely shared calculation, the full list runs to about 42 hours. On the UK version of the list: X-Men and X2; Captain America: The First Avenger; The Avengers; Avengers: Infinity War and Endgame; both seasons of Loki; Shang-Chi and the Legend of the Ten Rings; Doctor Strange in the Multiverse of Madness; Black Panther: Wakanda Forever; Deadpool & Wolverine; Captain America: Brave New World; Thunderbolts*; and The Fantastic Four: First Steps.

Spider-Man: No Way Home is on the US list but is not on Disney+ in the UK, so British viewers will need to find it elsewhere.

If you do not have 42 hours, a shorter route covers the essentials:

Avengers: Endgame, ideally with the Encore scenes, for the state of the Avengers and Doom's first tags.
Loki, especially season two, for how the multiverse works and why it is fragile.
The Fantastic Four: First Steps, for the Fantastic Four's world, Franklin and Doom's first appearance.
Thunderbolts*, for the team that ends the film calling itself the New Avengers and for the Fantastic Four's arrival.
The VisionQuest finale and its post-credits scenes, for Wanda.
X-Men and X2, if you have never seen the Fox films and want to know who Stewart, McKellen, Marsden, Cumming and Romijn are playing.

Deadpool & Wolverine is useful too, because it brought back Channing Tatum's Gambit, who returns in Doomsday. Everything else on the list will add to your enjoyment of the film but, on the evidence so far, is not essential.

The Comics Clue: Secret Wars

Doomsday is the first of two films. Avengers: Secret Wars follows, dated for 17 December 2027 in the US (no UK date has been announced), and it is also directed by the Russos. Its title comes from Marvel Comics, and the most influential version of that story is worth knowing as background, not as a prediction.

In Jonathan Hickman's Secret Wars (2015–2016), universes are colliding in events called incursions, each one destroying both worlds involved. When the main Marvel universe and its last rival finally collide, Doom, working with Doctor Strange and the Molecule Man, kills the godlike Beyonders who caused the destruction and takes their power. He then rebuilds the fragments of the ruined realities into a single patchwork planet, Battleworld, and rules it as God Emperor Doom.

The Endgame Encore scene of universes colliding, and an official logline about three universes on a collision course, make the echo hard to miss. But the MCU has used comics loosely before, and this is a guide to the ideas Marvel may draw on, not a forecast of Doomsday's plot.

What We Still Don't Know

A great deal. Marvel has not explained what Doom wants with Franklin, the Hulk or Wanda, or how the three universes are brought together. It has not said which characters several of its returning stars are playing, and it has not confirmed whether Doom is connected to Tony Stark. It has not confirmed whether any of the VisionQuest characters will appear. Those are the questions the film exists to answer, and an ending explainer will follow once it is out.

Doomsday arrives with more homework than any Marvel film before it, but the core of it is simple. Watch the scenes where Doom appears, understand that the multiverse is breaking down, and know which three families of heroes are about to meet. In the UK, you will be among the first to find out what Doom wants: from Wednesday 16 December, two days before America.

Sources

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James Taylor