The Thor trilogy secretly introduced the idea of the multiverse into the MCU well ahead of it being important in Ant-Man and, possibly, Avengers: Endgame. Through Phases 2 and 3, Marvel Studios has grown increasingly interested in the multiverse concept. This scientific theory has two strands to it; on the one hand, it covers the idea that history branches out, creating alternate timelines like the Mirror Universe in Star Trek. On the other, it posits that while we are three-dimensional creatures, there are other planes of existence. To date, the MCU has predominantly been interested in the latter, which explains the Quantum Realm in Ant-Man and the Dark Dimension in Doctor Strange.

The movies have actually been building up to this for quite some time. In fact, the first reference to the multiverse was in 2011's Thor; in the post-credits scene, Erik Selvig described the Bifrost as "a gate to another dimension," suggesting that Marvel originally intended every one of the Nine Realms to be in a different dimension. That idea was quietly dropped, though; presumably, the retcon explanation Selvig was simply mistaken about this point.

Related: How Loki Really Survived The End Of Thor

But look closely, and the Thor trilogy did indeed lay the foundations for the multiverse in the MCU. It just pulled it off in a very subtle, very smart way. Here's how Marvel's been building the Quantum Realm and beyond up all along.

Thor: The Dark World Mentioned 616 Universe And The Nexus Of All Reality

Erik Selvig Dark World Chalkboard

One key scene in Thor: The Dark World sees Doctor Erik Selvig, the noted astrophysicist now consigned to a mental institution, jotting notes on a chalkboard. It's a popular scene, involving a much-loved Stan Lee cameo, but the notes on the board are particularly interesting. Some of them are lifted from real-world science, especially from the theories of quantum mechanics, but others are comic-book specific. Crucially, many point towards a multiverse:

  • 616 Universe: In the comics, this is the traditional designation given to the Marvel Universe to distinguish it from all other realities. It was first used by The Daredevils #7 back in 1983, and was applied by the Omniversal Majestrix, Queen of a dimension known as Otherworld.
  • The Nexus of All Realities: This is a location in the Florida Everglades where parallel worlds sometimes intersect. It's commonly associated with the Man-Thing, who acts as its guardian.
  • The Fault: This is a rip in the fabric of the universe, which served as a gateway to a twisted alternate dimension known as the Cancerverse.
  • The Crossroads: Something of a deep cut into Marvel lore, the Crossroads is a gateway dimension through which other worlds can be accessed. It was introduced in Incredible Hulk #300 (1984) and later

Assuming Selvig's notes are correct, a lot of major Marvel multiverse ideas are established parts of the MCU lore.

Related: This Guardians of the Galaxy Theory Makes THOR 2 Worth It

Thor: Ragnarok Also Introduced The Man-Thing

Thor: Ragnarok added a new element to this, confirming the existence of the cosmic being known as the Man-Thing. According to Kevin Feige, the film's biggest Easter eggs were on the side of the Sakaaran Palace. The side was emblazoned with carvings of the Grandmaster's previous champions - and one of them was the Man-Thing, a character created in a partnership between Stan Lee, Roy Thomas, Garry Conway, and Gray Morrow back in 1971.

Dr. Theodore "Ted" Sallis was a scientist attempting to recreate the super-soldier serum, but he wound up pursued by A.I.M.; rather than allow the sole sample of the formula to fall into A.I.M.'s hands, he injected himself with it, and fled into the nearby swamp. The serum left him vulnerable to mystical energies that surrounded the Everglades, and he was transformed into the monstrous Man-Thing. The substance of his body was eaten away be vegetation; though he retains the semblance of humanity, in truth he is now a whole new life-form. The Man-Thing became guardian of the Nexus of All Realities, a breach in the fabric of time and space that binds all the various dimensions together.

Curiously enough, Thor: Ragnarok wasn't the first reference to the Man-Thing in the wider MCU. In Agents of S.H.I.E.L.D. season 1, a weary Maria Hill reflected that she was tired of being asked incessant questions by Congress. "Who or what is a Man-Thing," she quoted as an indication of the type of questions she was fielding. While that indicated the Man-Thing existed in the MCU, Thor: Ragnarok evidenced that it looked like the classic comic book equivalent, and was indeed able to traverse the dimensions (by going to Sakaar) - meaning he may also have accessed the Nexus of All Realities.

Page 2 of 2: The Multiverse In The MCU

Doctor Strange multiverse scene

The Multiverse In The MCU So Far

The last few years have seen Marvel commit wholeheartedly to the multiverse - although they haven't quite handled it the same way as the comics. The MCU imagines a scenario where there are entirely different planes of reality, ones that are traditionally beyond the reach of three-dimensional beings. In fact, sorcerers like Doctor Strange borrow power from these other dimensions, using it to reshape reality; with training, they can learn to access some of these dimensions, whether physically or in an astral form. The Multiverse was explored in detail in one scene of Doctor Strange, where the Ancient One cast Stephen Strange on a "Magical Mystery Tour" where he tumbled through countless different dimensions.

Related: Endgame Theory: The Quantum Realm's Secret City Houses New Avengers Villains

The movies have really explored only two key dimensions in depth. The first is the Dark Dimension, a strange and hostile universe that is ruled by the Dread Dormammu. Time does not work properly in the Dark Dimension, and hence powerful sorcerers such as the Ancient One are able to draw upon its power to lengthen their lifespans. Dormammu's consciousness appears to pervade the Dark Dimension, and it burns with a hunger to consume other planes of reality and absorb them into itself. Fortunately for Earth, Doctor Strange entered the Dark Dimension when armed with the Time Stone; Dormammu was unable to deal with the concept of time, and was forced to swear never to attack Earth again. Of course, it's unlikely he'll keep to his vow.

The second is the Quantum Realm. According to the theories of quantum mechanics, if you shrink to subatomic size you would enter a state where the laws of science - laws such as gravity or time - cease to apply. In the MCU, that is the Quantum Realm, a place outside space and time. It was introduced in the first Ant-Man film, and explored a little in Ant-Man & The Wasp, when Hank Pym attempted to rescue his long-missing wife Janet Van Dyne from it. The Quantum Realm appears to have a sort of "geography" to it; the deeper you go into the Quantum Realm, the more the laws of science break down.

There have been other references in the wider MCU as well. Guardians of the Galaxy Vol. 2 revealed that some creatures can move from one dimension to another at will; the film opened with an interdimensional creature attempting to consume the Sovereign's power batteries. Meanwhile, in Agents of S.H.I.E.L.D. season 4, Marvel Television revealed that the Ghost Rider is an interdimensional creature from a Hellish plane of existence, who transfers his consciousness from one host to another. Eli Morrow attempted to draw untold power from that dimension, and risked tearing the dimensional barriers apart. Meanwhile, in season 5 the team found themselves plagued by the Dimension of Dreams, suffering from nightmarish hallucinations. There have been references to other sources of extradimensional power as well, such as Zero Matter in Agent Carter and Cloak & Dagger. In Runaways, it's been hinted that Nico Minoru's Staff of One draws its abilities from the Dark Dimension.

The Multiverse In The MCU's Future

Scott Lang in the Quantum Realm in Ant-Man and the Wasp

The multiverse is sure to be an important part of the MCU going forward, and the Quantum Realm appears to be key. When Marvel first designed the Quantum Realm, they worked closely with Dr. Spiros Michalakis, a quantum physicist who found the concept thrilling. "This is exciting for the future," he explained in one interview. "There are different ways that some of these ideas appear on-screen in a few years. Not just for Ant-Man, but also for Captain Marvel and all of the Marvel Cinematic Universe." More recently, Michael Douglas agreed; "The Quantum Realm plays an important part in all the next chapters, I think, of the Marvel films," he observed. The Quantum Realm is known to play a role in Captain Marvel, perhaps as the source of Carol Danvers' Binary powers, and may explain Samuel L. Jackson's revelation that Captain Marvel can travel in time.

Related: How We Think Ant-Man Escapes The Quantum Realm In Avengers 4

It's generally believed that Avengers: Endgame is a time travel story, with the Avengers using the Quantum Realm to travel through time and attempt to rewrite history in order to avert or undo the snap. In terms of quantum theory, access to a subatomic dimension like the Quantum Realm could indeed enable that, and Ant-Man & the Wasp established that there are mysterious "time vortexes" in the Quantum Realm that could theoretically enable time travel. Tie-in merchandise has shown the Avengers wearing new white costumes that are reminiscent of Hank Pym's Quantum Realm environment suits, presumably to allow them to safely explore this strange plane of reality.

Looking beyond the next two films, Doctor Strange 2 is in the works, with Scott Derrickson signed up to return as director; it's safe to assume that film will continue to explore the multiverse. Meanwhile, Marvel Television looks set to tap into other dimensions in both Runaways and Cloak & Dagger. The mysterious mystical corruption Nico suffered while using the Staff of One has yet to be explained, and both Cloak and Dagger draw their power from other dimensions. Finally, there's even speculation that Agents of S.H.I.E.L.D. season 6 could feature an alternate-reality version of Coulson. It's clear the multiverse is in the MCU to stay.

More: How The MCU Will Look Completely Different After 2019

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