Over the course of the last ten years of the Marvel Cinematic Universe, both characters and audiences were gradually introduced to the six infinity stones, with each one possessing so much cosmic power that were they to be brought together the wielder could bring an end to all of creation as seem in Avengers: Endgame. Though we had seen the majority of the stones, one of them, the Soul Stone, continued to remain a mystery.
Finally revealed in Avengers: Infinity War, and just being another round rock only this time colored orange, it turns out that early in production, the Russo brothers had considered making the Soul Stone something else entirely: Captain America himself.
Captain America is the Soul Stone? That all sounds a little confusing. Which is likely why the idea was dropped as quickly as it was suggested. Still, the idea of making the Soul Stone an actual person, rather than just another rock, let alone a founding member of the Avengers, would certainly have been a unique surprise. How exactly this would have worked though is anyone's guess. Was Captain America bonded with the stone at some point and was unaware of this? Or maybe, due to Cap being of such pure soul, he had become the embodiment of the power without knowing.
There is no doubt a way of making it work, but they all surely end with Captain America having to make some sort of sacrifice in order for the power to be obtained. If not, Cap would have had to have been separated from the power somehow, as Thanos would have had a difficult time shoving Steve Rogers into the designated space on his Infinity Gauntlet.
There is some semblance of the idea still intact in Avengers: Endgame, with Johann Schmidt, Captain America's former enemy The Red Skull, being revealed to be an ethereal spirit serving as the stone's guardian. He is bonded with the Soul Stone in part, unable to leave the planet on which it rests, until somebody claims it.
In Avengers: Infinity War, Thanos encounters Schmidt, and per his instructions, makes the ultimate sacrifice, in this case murdering his adopted daughter Gamora in order to claim the stone. In the altered continuity of follow-up Avengers: Endgame, Clint Barton and Natasha Romanoff battle one another to serve as the sacrifice so that the other could claim it. This ends with Natasha falling to her doom, and Clint holding the coveted stone.
There is also some similarity in the pages of Marvel comics and the idea of a person being the Soul Stone, with Adam Warlock at first possessing it before his own soul becomes a part of it.
Avengers: Endgame was directed by Anthony and Joe Russo and written by Christopher Markus and Stephen McFeely, and features an ensemble cast including Robert Downey Jr., Chris Evans, Mark Ruffalo, Chris Hemsworth, Scarlett Johansson, Jeremy Renner, Don Cheadle, Paul Rudd, Brie Larson, Karen Gillan, Danai Gurira, Benedict Wong, Jon Favreau, Bradley Cooper, Gwyneth Paltrow, and Josh Brolin. It is now available to watch on Disney+. This comes to us from The Russo Brothers' Twitter account.