Incursions Explained: How Two Universes Kill Each Other in the MCU

An incursion is the only thing in the MCU that can kill a universe outright, and the film that introduced it spent about ninety seconds explaining it. Doctor Strange in the Multiverse of Madness defines it, demonstrates it and then moves on, which is why four years later a large share of the audience can name the word without being able to describe the mechanic.

With Avengers: Doomsday built around heroes from three distinct universes on a collision course, this is the single most useful piece of MCU cosmology to actually understand. So here is the whole thing, from the on-screen definition outward.

The On-Screen Definition

An incursion happens when the boundary between two universes erodes, and they collide — destroying one, or both.

That line, delivered on Earth-838, is the load-bearing sentence. Three things follow from it and all three matter.

1. An incursion is not a portal or a doorway. It is structural failure — two realities occupying the same space until the space stops working.
2. It is not necessarily symmetrical. One universe can die while the other survives, which is what makes the whole concept usable as a threat rather than a mutual suicide pact.
3. It is caused. Universes do not routinely drift into each other; something has to erode the boundary first.

What Actually Causes One

The film gives two causes and implies a third. The first is dreamwalking — possessing the body of a variant across realities. The Darkhold describes it, Wanda Maximoff uses it, and the Illuminati of Earth-838 execute their own Stephen Strange specifically because his use of it caused an incursion that destroyed another universe. That is not subtext; a council of heroes states it as their justification for killing one of their own.

The second is uncontrolled universe-hopping. America Chavez punches star-shaped holes between realities without knowing how, and the film treats every one of those crossings as damage. The third, implied rather than stated, is simply repeated traffic: the more the boundary is crossed, the thinner it gets.

The Rubble We Have Already Seen

The most underrated scene in Multiverse of Madness is a wordless one. Strange and America fall through a sequence of realities and land, briefly, in a dead one: a universe reduced to floating debris, no light, no survivors. The film does not stop to caption it. It is showing you an incursion's aftermath so that when the word is used later, the audience already has the picture.

The scene does two jobs. It proves that at least one universe in the MCU's multiverse has already been destroyed this way, and it establishes that the destruction is total rather than a defeat somebody could reverse. Nothing in the franchise so far has undone an incursion.

The Comics Origin, and Why It Matters Now

Incursions come from Jonathan Hickman's New Avengers, launched in 2013, and the concept there is more brutal than the film version. Two Earths approach; the only way for one to survive is to destroy the other's Earth before the collision completes. That premise forced Marvel's Illuminati — including Reed Richards and Doctor Strange — into serially destroying other populated worlds to save their own, and it ran directly into the 2015 Secret Wars, where the last two universes collide and Doom salvages the wreckage into a single patchwork planet.

Reporting has consistently linked Avengers: Secret Wars to that storyline. Marvel has confirmed no such structure — but the MCU has already imported the vocabulary, the Illuminati and the moral problem, which is a lot of groundwork to lay for a concept you do not intend to cash. Our reset analysis weighs how likely that is.

Five Things Fans Get Wrong About Incursions

• They are not the same as the Sacred Timeline branching. Branching creates new realities; incursions destroy existing ones. Different mechanic, different show — see our branching explainer.
• The TVA does not police them. Nothing in Loki suggests the TVA has jurisdiction over collisions between separate universes, only over deviations within one.
• Not everyone who crosses realities causes one. Spider-Man: No Way Home moves people between universes wholesale without an incursion; the erosion appears to need repetition or possession.
• An incursion does not require a villain. It is presented as physics, which is why the Illuminati's atrocity is framed as a choice made under real constraint rather than cartoon evil.
• 'One or both' is doing real work. A film can therefore end with one universe surviving an incursion, which is precisely the escape hatch a franchise reset needs.

The Piece Still Missing

The MCU has shown one dead universe, one execution justified by an incursion, and no on-screen incursion in progress. That gap is conspicuous. Every element of the concept has been taught to a mass audience except the spectacle, and spectacle is the one thing a Russo brothers Avengers film is built to deliver.

If you want the wider map, our Earth-838 explainer covers the one universe the MCU has toured in detail, and our three-universe breakdown works through which realities are actually on the collision course.