Over the past few months, we've seen increasing evidence that the Quantum Realm will play a significant role in undoing the Infinity War deaths in the upcoming Avengers 4 movie. Michael Douglas talked about the importance of the Realm and the director of Ant-Man and The Wasp gave us even more details about what's hidden inside the Quantum Realm. Now we have Marvel's top boss Kevin Feige going on the record about the massive importance of that particular universe.
It's widely expected that Ant-Man will use the Quantum Realm to travel through time, and that other Avengers may do the same, given that the main time-traveling tool, the Time Stone, isn't available. But Feige's newly discovered comments — even if they don't mention anything about the next Avengers film — seem to confirm the importance of the Realm for the upcoming MCU movies, Avengers 4 included. After all, Marvel must have planted that Quantum Realm scene in Ant-Man 2 for a reason that relates to Avengers 4.
Feige's remarks come from an interview published in a collector's edition hardcover book celebrating the 10-year anniversary of the MCU, via ComicBook:
At the end of Ant-Man we followed Scott Lang into the Quantum Realm for the first time. We were beginning to peel back the onion that would later be completely peeled back in Doctor Strange as we go into the multiverse. So that was our little test into that.
But now the Quantum Realm is a whole other territory that we can play with to tell our stories. This Quantum Realm is much larger than we ever imagined, and there are all sorts of adventures to be had at that level, which perhaps we will explore in another film.
We know from Ant-Man 2 that there are time vortexes in the Quantum Realm that Scott Lang needs to be aware of. We also know from the deleted scenes of the movie that there are smart creatures in there, which Janet van Dyne could interact with. The director of the film, Peyton Reed, also revealed there's a whole city teased in Ant-Man 2. So yes, everything that Feige said about the Realm has been hinted at before. There's even a fan theory that says the souls of the dead go to the Quantum Realm, with some arguing that's precisely what happened with the victims of the snap. But Feige talking about the Quantum Realm's importance for the MCU is a clear sign that we'll see Realm action in Avengers 4.