For what feels like forever, Marvel Cinematic Universe fans have been theorizing about where the Soul Stone, the last Infinity Stone unaccounted for, is located. Is under Odin’s eyepatch? Hidden in Wakanda? Are Heimdall’s all-seeing eyes actually the Soul Stone?
These fans theorize that the Soul Stone is or is within Tony Stark.
Some version of this theory has been around for a while but the new Avengers: Infinity War promotional materials that seem to link Tony Stark to the Soul Stone has given it new life. Another piece of the puzzle is Howard Stark’s video message to Tony in Iron Man 2. In that video, Howard reminds his son that “What is and always will be my greatest creation, is you.”
The idea is that Howard somehow turned the Soul Stone into Tony Stark, much like how some of the other stones have taken different forms like the Aether and the Tesseract.
How the Soul Stone would have come to Earth is unclear, though it should be noted that the Tesseract was on Earth for centuries and that, in the Marvel Comics universe at least, the Infinity Stones are drawn to one another. If the Soul Stone did appear on Earth, Howard Stark’s ties to SHIELD mean that he would likely be one of the scientists enlisted to examine it.
Another piece of evidence backing the theory up is that Howard and his wife had Tony pretty late in life. Not late enough to make it impossible to believe Tony was born the old-fashioned way, but late enough to make someone wonder why a man like Howard, who had spent his whole life dedicated to work and showing little interest in family, would suddenly decide to have a child. Perhaps the truth is that Howard’s child was his work.
Another possibility being discussed is that the Arc Reactor is somehow related to the Soul Stone. This is a less clean narrative possibility since Anton Vanko was also involved in the creation of the Arc Reactor. Some suggest that the Arc Reactor being the Soul Stone would also explain why Loki’s scepter was unable to pierce the Reactor in The Avengers, but it's important to remember that the version of the Arc Reactor in Tony’s chest was not the original but a miniaturized version of his father’s work. It seems like if there was a tie to an Infinity Stone there, fans would have seen it on screen already. Even so, if Tony himself is the Soul Stone that would also explain why Loki’s scepter failed to mind control him.
A last variant of the theory is that when Tony Stark created a new element in Iron Man 2 he inadvertently created a sixth Infinity Stone. This seems particularly unlikely since, as brilliant as Tony is, he does not possess the kind of cosmic power that the Celestials who created the other Stones do. Also, as far as we know, the Infinity Gauntlet has always had six slots, so it would strange for there to have only been five Infinity Stones previously.
There’s some other random bits of evidence for these theories (h/t Times Now), like the Arc Reactor that powers Iron Man’s armors making sounds similar to those of the Tesseract-powered Hydra weapons created by the Red Skull, or a scene in the Avengers: Infinity War trailer where Tony is moving while his friends appear to be frozen in place, or some recontextualized dialogue between Tony and Nick Fury in some of the Iron Man movies. These are disconnected, uncontextualized, and not entirely solid bits of information that don’t really form a narrative picture.
Fans will have to wait until Thanos arrives in Avengers: Infinity War to know for certain.
Avengers: Infinity War on April 27th. Black Panther is now in theaters. Other upcoming Marvel Cinematic Universe movies include Ant-Man and the Wasp on July 6th, Captain Marvel on March 8, 2019, the fourth Avengers movie on May 3, 2019, the sequel to Spider-Man: Homecoming on July 5, 2019, and Guardians of the Galaxy Vol. 3 in 2020.