In a tweet regarding Avengers: Endgame, the Russo brothers revealed that Captain America almost was… the Soul Stone – but how did this happen?
In Avengers: Infinity War, the Soul Stone still holds many secrets – even that, throughout the 18 films of the Marvel Cinematic Universe, the Power, Reality, Time, Space, and Mind Stones have appeared in various forms, except for the Soul Stone. Until this film, we learn that it belongs to a planet called Vormir, and is guarded by Red Skull. To obtain it, one must exchange a “soul for a soul,” sacrificing a life for its power.
In both Endgame and Infinity War, obtaining the Soul Stone resulted in the “execution” of two characters: Gamora and Natasha Romanoff. However, during the script development, the Russo brothers revealed that the Soul Stone almost did not belong to the planet Vormir, but that Captain America himself, Steve Rogers, was the Soul Stone – but how would this work?
In the Marvel Cinematic Universe, the Infinity Stones are shaped like gems of various colors. Some are integrated into artifacts, like the Tesseract or Aether, but they remain tangible materials. So how does this make Captain America the Soul Stone? Is it inside his body, or has he always been the physical embodiment of this stone?
After the events of the Infinity Wars comic from 2018-2019, Adam Warlock granted these stones knowledge to find a host for himself. The Time and Reality Stones linked with different people from Earth. This could also apply to Steve – his brave and pure heart attracted the Soul Stone and fused with Captain America’s body. This makes sense for the scene where he faced Red Skull – as Red Skull is also the guardian of the Soul Stone.
But if that were the case, it would mean Thanos would have to kill another Avenger to collect another Infinity Stone – which would overlap with Vision’s death. This is one of the hypotheses as to why it was not applied to the final script by the Russo brothers; another reason is that Steve was a crucial factor in the final battle against Thanos – when he lifted Mjolnir and saved Thor from danger. If so, it would mislead fans to question whether he truly deserved to lift the hammer or if it was just the power of the Soul Stone helping him (like a pure soul deserving to wield it). Due to the complexity of successfully adapting this, Joe and Anthony Russo changed and decided to place the Infinity Stone on the planet Vormir.