Doctor Doom's Mystery Device in the Avengers Doomsday Trailer Might Be the Ultimate Nullifier

There is a small but massive detail hiding in the Avengers Doomsday trailer involving Doctor Doom, a mystery device, and a suit change that could tell us exactly what happens between Victor von Doom and Reed Richards in this movie. This matters because it could hint at the actual twist the Russo Brothers have been building toward with Robert Downey Jr.'s version of Doom.

In the trailer, Doom smashes through a window with his back facing us while an object flies next to him. My first thought was that this was Mjolnir knocking him out, but something else appears to be happening. Doom reconfigures himself midair and lands confidently facing forward, and by the time he lands he is wearing his alternate suit, the one with a single cape clasp and a smoother mask without the visible armor that I saw at the Marvel TVA walkthrough experience at D23. That is a different suit than the heavily armored, double clasp version we see Doom wearing in most of the rest of the footage.

The trailer's editing makes it look like this is part of Doom's fight with Thor, but the timeline does not match

The structure Doom smashes out of also appears at the 1:29 mark in the wide shot of Doom flinging Stormbreaker out of Thor's hand, and in that shot Doom is wearing the more armored suit and the window is not yet broken. That tells me the fight with Thor continues into this structure, where Doom eventually gets knocked out wearing the alternate suit, unless there are simply multiple versions of this structure, which I am not ruling out.

An Iron Studios figure reveals a spell book and a mystery rectangular device in Doom's hand

Recipients of the Iron Studios Dr. Doom figure for Avengers Doomsday have noticed details about his hands. One attachment is described as Doom's official spell book for this movie, with runes and markings that match the sigil on his gauntlet. I think this could be Doom's Book of Vishanti, or maybe the Darkhold, or the Book of Cagliostro from the 616 universe. On that note, the trailer also gives us a glimpse of what look like the Latverian witches at the 42 second mark, standing behind Doom in an overhead shot of the throne room once you brighten the image.

But another attachment for the figurine shows Doom holding a specific rectangular device. The channel Just The Nobodys noted this in their unboxing video but oddly did not go into detail about it, saying only, "So this device we will not talk about right now." I think this small rectangular device is what flies next to Doom in the window smashing shot, and it might also be what Victor is holding in his hand in the scene where Reed confronts him.

Is the device the Ultimate Nullifier, or something else entirely

The prevailing theory online is that this device is the Ultimate Nullifier, though I honestly do not know where that theory started or why people are so convinced of it. My own first instinct, based on its color, was that it is Doom's teleporter device, similar to the time door platform John Krasinski's Reed Richards uses in Multiverse of Madness, which the artists on that film said was based on Doom's time door from the comics.

Still, playing along with the Ultimate Nullifier idea: the device dates back to the Fantastic Four Galactus arc from 1966, where it was recovered by Johnny Storm from Tau 2 under the Watcher Uatu's direction so Reed Richards could threaten Galactus into leaving Earth alone, essentially a doomsday device that can undo an entire galaxy. In more recent comics from 2022, we learned the device was actually made by the Watcher Nu, and unlike the TVA's pruning rod, which just banishes people to the void, the Ultimate Nullifier completely erases something from all existence, rewriting reality so it never happened. If this is an MCU version, I wonder if it might function more like an ultimate pruning rod, something that bypasses the TVA's technology and lets Doom banish anything to the void as he builds Battleworld.

I find it notable that the Ultimate Nullifier never showed up in Fantastic Four: First Steps, despite that film being a fairly faithful adaptation of the Galactus storyline. Instead, Johnny Storm's journey to glimpse the Silver Surfer's home world ended up being what helped defeat Galactus.

A theory on how Victor von Doom could have obtained the device

I floated the idea that after the events of Fantastic Four: First Steps in the 616 universe, Latveria could have been one of the countries mobilized to build Reed's teleportation platforms, platforms that were mostly wrecked by the Silver Surfer. In the aftermath, with Reed getting credit for defeating Galactus and Victor already having lost his wife and child, Victor might build his own answer to that kind of threat, something that spirals into a weapon that can erase anything from existence.

What Reed's confrontation with Doom could actually mean

Back in the trailer, Reed could be furious at Victor for using this device to unmake something, possibly a version of New York we see in the footage, or even the entire 616 universe. I am a little worried that Reed being this angry in Doom's face could end badly for Reed himself, which might explain why Sue seems to be grieving Reed when she opens the trailer describing Victor as the smartest guy in every room.

The two Dooms theory involving Robert Downey Jr. and Cillian Murphy does not add up for me

There is a theory going around that there are two Victor von Dooms in this movie, one played by Robert Downey Jr. and one played by his Oppenheimer co-star Cillian Murphy. In a 2025 interview, one of the Russo Brothers said Kevin Feige came up with the idea of bringing Downey Jr. back, explaining, "that conversation was had a while ago and then Robert tried to talk us into doing it and we said no. Weirdly because we said we would come back. We just didn't have a story. We didn't have a way in. And then one day Steve McFeely who's one of our key collaborators said I have an idea. And he called us to pitch and we went that's the story. That story has to be told." The same Russo Brother added, "We love villains who think they're the heroes of their own stories. That's when they become three-dimensional and when they become more interesting. And when you have an actor like Robert Downey, you have to create a well-shaped three-dimensional character for the audience. That's where a lot of our focus is going."

People have also pointed to a July 2023 interview where Josh Horowitz asked Cillian Murphy if he would ever play Doctor Doom, and Murphy responded, "Dr. Doom is different than Scarecrow... as long as the script and the person's there, then sure, we can talk," adding, "I'll read, you know, if someone sends me a script, I'll read it. And you never know what turns up."

I think Cillian Murphy would make a perfect Victor von Doom for the MCU beyond Secret Wars once Robert Downey Jr. eventually steps away, but I find this specific two Dooms theory too convenient. As I put it, "guys, I live in this town. I know how this industry works, and it is really hard to keep a secret that big, an actor like this making not just a one scene cameo, but sharing the title role of the movie." With hundreds of people involved in a decision like that, agents, publicists, managers, lawyers, and union staff, I think we would have heard rumors the way we did about Tobey Maguire and Andrew Garfield roughly 12 months before No Way Home came out. There is also a small mole visible by the right eyelid in the close up shot of Doom's eyes in the trailer, matching a blemish Robert Downey Jr. has in other bright close ups from Marvel films and press photos. So while there could still be more than one Doom in this movie, in that shot and every shot of Doom's eyes we have seen so far, it is Robert Downey Jr.

Why Doom might be wearing two different suits

My theory is that Doom initially presents himself to the heroes in the unarmored, single clasp Latverian suit to appear more diplomatic and less threatening, then switches to the heavily armored, rune covered suit once he is forced to reveal what he is really doing and the Avengers turn on him. That would help explain why Reed looks so shocked in the moment he asks Victor if he did this.

Marvel's official Doomsday rewatch list leaves out some notable films

Marvel Studios released an official list of 15 essential titles to rewatch before Avengers Doomsday: X-Men (2000), X2 (2003), Captain America: The First Avenger (2011), The Avengers (2012), Avengers: Infinity War (2018), Avengers: Endgame (2019), Loki seasons 1 and 2, WandaVision (2021), Spider-Man: No Way Home (2021), Black Panther: Wakanda Forever (2022), Captain America: Brave New World (2025), Deadpool and Wolverine (2024), Doctor Strange in the Multiverse of Madness (2022), Thunderbolts (2025), and Fantastic Four: First Steps (2025). Notably absent are Iron Man (2008), Captain America: The Winter Soldier (2014), Avengers: Age of Ultron (2015), Thor: Love and Thunder (2022), Ant-Man and the Wasp: Quantumania (2023), and The Marvels (2023).

Do you think that mystery device in Doom's hand is really the Ultimate Nullifier, or something else entirely?