As we inch closer to Avengers: Infinity War's arrival, we still have no definitive answer as to where the final Infinity Stone is hidden. The Soul Stone is the last to be located in the Marvel Cinematic Universe, but in Marvel Comics’ Avengers: Infinity War Prelude #2, Wong revealed to Doctor Strange that it’s the biggest threat of them all.
That... doesn’t sound good for Earth’s Mightiest Heroes. Whilst Doctor Strange doesn’t seem particularly worried about the potential threat, Wong assures him that if someone assembles all of the stones together, “We will need to prepare for the greatest battle this universe has ever seen.” Indeed they will, and though we're not certain what abilities the Marvel cinematic Universe's version of the Soul Stone possesses, we can look to its comic book counterpart for some clues as the what the Avengers can expect to face.
In the comics, the Soul Stone has the ability to absorb souls into itself and gains all the knowledge that those souls have. It wouldn’t be surprising if the MCU version is similar, and that Thanos will use this ability to learn the location of the rest of the stones. Trapping a person’s soul inside the stone could also be used as a way to bring characters back from the dead in a future film, most likely the currently untitled Avengers 4. Once Loki gives him the Space Stone (which we appear to see in the first Infinity War trailer), Thanos simply has to follow the trail to Xandar for the Power Stone, Knowhere for the Reality Stone and, finally, to Earth for Doctor Strange’s Time Stone and Vision’s Mind Stone. The Soul Stone can also reveal the truth from other people, so the Mad Titan will know when people are lying to him.
But one of the most intriguing abilities that the Soul Stone possesses is that it can also trap a person’s soul inside itself. There, they believe they are in a perfect world, with everything they could wish for. Fans of Marvel Comics’ “The Infinity Gauntlet” story know that Adam Warlock is an integral part of the plot, since he had the Soul Stone embedded into his head, similar to how the Vision is powered by the Mind Stone in the MCU. Since James Gunn confirmed that Adam Warlock won’t be appearing until a future Guardians of the Galaxy film, it’s possible that the Vision will take Adam Warlock’s integral place in the story.
But even if Vision does take Warlock’s place in this film, we still haven’t been shown where the Soul Stone is being kept. Many assumed that since Black Panther is the final film before Infinity War, and one of the action sequences in the Infinity War trailer took place in Wakanda, that the Soul Stone would appear there. That... was not the case, though there is a chance that it could still appear in the African nation during Avengers: Infinity War.
A portion of the mythology Black Panther explored had to do with the afterlife. Once T’Challa and Killmonger drank the essence of the Heart-Shaped-Herb, they visited the Djalia, the Wakandan afterlife. There they met the souls of their respective fathers. Since the film explained that Wakanda was built on the foundations of a huge meteorite of pure Vibranium, that could be the explanation behind the Soul Stone being in the country. If it was encased in the heart of the meteorite, the powers of the Stone might absorb the souls of people who live there, manifesting themselves as the people T’Challa and Killmonger visited in the Djalia.
We already know that Thanos is a formidable villain, but give him all the powers of the six Infinity Stones at his disposal, and it’s a terrifying thought. The Soul Stone is a sentient being itself and can literally attack the very fibre of what makes the Avengers so resilient. What is Captain America without his soul, for example? If Thanos can just absorb all of them into the Soul Stone, then the threat is incredibly intimidating. Thanos is coming, and the Soul Stone will be his biggest weapon.
Directed by Joe and Anthony Russo, Avengers: Infinity War stars Robert Downey Jr., Chris Evans, Chris Hemsworth, Mark Ruffalo, Jeremy Renner, Scarlett Johansson, Anthony Mackie, Paul Rudd, Elizabeth Olsen, Tom Holland, Benedict Cumberbatch, Chadwick Boseman, Chris Pratt, Zoe Saldana, Dave Bautista, Bradley Cooper, Vin Diesel, Tom Hiddleston, and Josh Brolin. The film opens April 27.