Ever since Avengers: Endgame stormed cinemas and became the biggest blockbuster of all time, fans and critics have had one question on their mind: How do you possibly top that? After saving all of reality from a cosmic threat, what more can you do to up the ante for the next phase of the MCU? Marvel showrunner Kevin Feige provided the answer during an interview at CCXP.

"When we first started the MCU, it was all about Tony Stark. Introduce the world to Tony Stark and that Iron Man armor. Then [we] went on to teach people what Asgardians were and learn about super soldiers then bring them together in Avengers. I've always loved space movies and I've always loved big intergalactic tales, which is why we did Guardians and the audience came with us so we could do a movie like Endgame. RELATED: Sam Raimi Explains Why He Directed Doctor Strange 2 After Spider-Man 3 Backlash

I always wanted to do time travel, which we finally got to do in Endgame. The multiverse is the next step in the evolution of the MCU and Doctor Strange in the Multiverse of Madness is going to crack it open in ways that will have repercussions for a Disney+ series before it that's not WandaVision and for movies after it in a big fun way."

So Marvel's response to the challenge of coming up with a bigger threat involves redefining the MCU's very concept of reality itself. Until now, it was a single universe that was in danger due to the actions of the Mad Titan Thanos. But in the next phase of the MCU, it will be multiple realities that exist in the same space but different dimensions that will be under threat.

The Multiverse is a sci-fi concept that has been gaining greater popularity in pop culture in recent times, thanks to shows like Doctor Who and Rick and Morty. A multiverse is created from the branching realities that are a result of random chance or conscious choices that split a single reality into multiple versions, each a separate manifestation of a choice.

So one universe within the multiverse would have a reality where Steve Rogers became a supersoldier, while another reality would have Peggy Carter take up the role. The Multiverse has long been a part of Marvel comics, and various universes within the Marvel multiverse are shown to exist side by side, with different versions of the same heroes existing on their Earths in each of these realities.

It's a pretty hefty concept to wrap your head around, but it also allows Marvel to create stories about different iterations of the same characters, some good, some evil and some simply bizarre.

Going forward, it will be Doctor Strange in the Multiverse of Madness which will introduce the concept of the Multiverse into the MCU. The film is billed as Marvel's first attempt at a horror film, which means it is more than likely that we will be introduced to some horrifying alternate versions of MCU characters, perhaps something like the Zombie Avengers from the comics. It will be interesting to see how the heroes react to the knowledge of their alternate-Earth counterparts, some of whom are sure to cause trouble for the MCU in the coming days. ComicBook.com.