10 Best Avengers 4 Fan Theories
3. Soul World
One of the most prevalent theories about what actually happened to all of the disintegrated heroes is that they're actually trapped inside of the soul stone.
In the comics, Soul World is a pocket dimension inside of the soul stone that houses all of the souls swallowed up by the stone. One of the most crucial storylines in the comics featured the Avengers thinking Adam Warlock was dead, only to realize he had just been sucked into Soul World. They subsequently freed him from it and defeated Thanos in the process.
In the MCU, this is plausible for several reasons. First off, it would be an easy way to bring back all of the heroes, as Marvel is want to do. But more importantly, the Russos themselves even confirmed that Thanos' final interaction with the young version of Gamora was inside of Soul World. While they went on to elaborate that doesn't necessarily mean Gamora is alive in there (far more likely that she's just a representation Thanos' psyche, which is why she's a child), it does confirm that Soul World exists in the MCU.
It's also important to note that Infinity War went to great lengths to explicitly show what each and every stone in the gauntlet did... except for the soul stone. The soul stone remains the most mysterious stone of all, and viewers can absolutely count on its power being revealed and very important to the plot in Avengers 4.