Avengers: Doomsday is going to be the biggest multiverse entry in the Marvel Cinematic Universe so far, and a new theory explains how Endgame could impact its multiversal story in a key way. The MCU’s Avengers movies are undoubtedly the most successful in the franchise. Over the years, they grew in scope, going from the original Avengers team to MCU-wide events.

Avengers: Doomsday will follow the lead of Infinity War and Endgame before it, as a major crossover event. That is made clear by the cast of the next Avengers movie, which includes returning MCU veterans, Multiverse Saga new stars, and even Fox’s original X-Men, with more rumored/expected to be part of the upcoming MCU movie.

In the comics, incursions were key to 2015’s Secret Wars, which inspired 2027’s Avengers: Secret Wars. An incursion is the event that happens when two universes collide and one or both of them are destroyed. Several incursions eventually led to Doctor Doom’s Battleworld and the end of the multiverse in the comics. Avengers: Endgame shows how Doomsday could do the same.

The MCU Already Showed How An Incursion Is Destructive

While incursions might be relatively new to the MCU, they have already been explained by a major Marvel movie, with a catastrophic incursion displayed in Doctor Strange in the Multiverse of Madness. The Doctor Strange sequel is one of the biggest MCU entries when it comes to the multiverse, introducing or expanding on key multiversal terms and elements for the franchise.

The film featured an incursion related to a Doctor Strange variant. When Benedict Cumberbatch’s Doctor Strange from the MCU found himself in the world of his evil variant, Sinister Strange, he experienced first-hand what the destructive force of an incursion looks like. Sinister Strange’s world is shrouded in darkness, with the sky broken, buildings floating into nothingness, and so on.

The evil version of Doctor Strange caused the incursion that destroyed his universe by dreamwalking, projecting himself onto the bodies of multiversal Doctor Strange variants several times. Eventually, the mark he left on the multiverse was too great to be ignored, with Sinister Strange’s universe on the losing end of an incursion, destined to be destroyed. Incursions are no joke.

Avengers: Endgame Messed With The MCU’s Timeline To Create Incursions – Marvel Theory

Based on the MCU’s rules, incursions are related to changes to a timeline/universe that should not happen. That is shown by what dreamwalking did to Sinister Strange’s universe and the TVA’s original mission in Loki of pruning timelines that diverged from a set path. Based on that, a new Avengers: Doomsday theory connects the movie’s multiverse mayhem to Endgame.

The 2019 Marvel film saw the invention of time travel in the MCU. The Avengers then executed the Time Heist, which allowed the heroes to retrieve the Infinity Stones and use them to save the people Thanos erased from reality and defeat the Mad тιтan. While the Avengers ultimately won in Endgame, the Avengers: Doomsday theory shows how they might have lost.

Endgame saw the heroes’ plan cause many changes to the MCU timeline: 2014’s Thanos follows them to the future, Loki escapes with the Tesseract after his original version died, two Nebulas meet one another, and Captain America stays in the past with Peggy Carter. Those changes created branching timelines, which can continue to change based on new decisions.

Given how Sinister Strange’s meddling with other universes caused his world to suffer an incursion, the Avengers: Doomsday theory suggests that Endgame‘s time travel could lead to the upcoming MCU movie seeing the main Earth facing the consequences of the changes the heroes made to the timeline. The Avengers might have defeated Thanos, but doomed their universe and others.

Avengers: Doomsday Already Has Three Major Incursions Waiting To Happen

Besides the possibility of an incursion due to Avengers: Endgame‘s events, the MCU’s next Avengers movie should have at least three other incursions to deal with. In the Doctor Strange sequel, Stephen Strange’s dreamwalking to stop the Scarlet Witch accidentally created an incursion, as revealed by Charlize Theron’s Clea. He entered the Dark Dimension to help her fix it.

In The Marvels‘ post-credits scene, Monica Rambeau gets trapped in a universe with Fox’s X-Men. With many actors from that franchise returning as their characters in Avengers: Doomsday, her presence there could lead to an incursion with the MCU’s main Earth. Finally, the Fantastic Four’s MCU arrival — seen by their spaceship in Thunderbolts* — could lead to their universe colliding with Earth-616.

How Doctor Doom Could Fit In With The MCU’s Incursions

According to an official synopsis for Avengers: Doomsday (via MovieWeb), Robert Downey Jr.’s Doctor Doom “will unleash a cascading crisis across the multiverse.” Based on that and the incursions already set up for the MCU’s next Avengers movie, it seems like the villain could be causing new incursions to happen. Perhaps we might have even seen the start of one.

Interestingly, the Fantastic Four spaceship in Thunderbolts*‘s post-credits scene is different from the one in the team’s MCU debut movie. Additionally, Marvel Studios President Kevin Feige has teased that someone else could be on the ship. If Doctor Doom were the one in it, he could be the cause of an incursion between the Fantastic Four’s universe and the main MCU in Avengers: Doomsday.