Forget #Justice4Haweye, the Soul Stone is the OG mystery of Avengers: Infinity War. The epic blockbuster will see almost the entirety of the MCU coming together to prevent Thanos from acquiring the six Infinity Stones and with them mastery over all of reality. Five of the stones have thus far been featured over the course of 10 years but the final stone has yet to appear. This has led some fans to develop dozens of theories about the location of the Soul Stone before the answer is finally revealed.
Avengers: Infinity War has been an incredibly secretive movie, but that has not stopped fans from pouring over every inch of information available. Piecing together footage from trailers, set leaks, the barest of teases, and a pinch of comic book knowledge, fans have done their detective work to track the final stone. Some theories are strong. Some are just plain wacky. All of them are fun. Here are some of the biggest ones you need to know.
The Soul Stone Is On Titan
Let's get the obvious and perhaps the strongest theory out of the way first. Titan is the homeworld of Thanos and we know that it's been desolated by some catastrophe decades ago. There are no hints as to what this extinction level event was but the strong money is that it has to do with the Soul Stone. Infinity Stones hold great power and it wouldn't be the first time one was used to wipe out a planet. If the stone did kill his world, it makes sense that Thanos would avoid it for emotional reasons. Plus, the planet is orange, the same color as the Soul Stone, which is probably not a coincidence.
It's Been In Wakanda The Whole Time
Before Black Panther released and became the highest grossing superhero movie ever made, there was a solid chance that the Soul Stone would be revealed to be in Wakanda. That was not the case, and Ryan Coogler purposefully left the stone out of his movie, but some fans are having a hard time letting go. Some theories state that the Soul Stone was in the vibranium meteorite that crash-landed in what would become Wakanda. It's buried deep within the Earth and is what gives the Heart-Shaped Herb it's power (and all the kooky visions). At this point, the chances aren't great this will end up being the case, but it was a fun theory to think about.
Heimdall's Beautiful Eyes
He can see every soul in the universe, and some people don't think that's just a poetic choice of words; it might be literal. Heimdall's eyes may actually be the Soul Stone, due to his ability to see anything in the entire universe. His eyes are also a orange-ish color which matches the stone. This is an interesting one, but I have my doubts. Vision and Doctor Strange already fill the quota of characters who are in immediate danger for possessing Infinity Stones and both of them are more well-loved than Heimdall. We don't really need a third guy doing something two other characters do better.
This one is my personal favorite and also probably the most coincidental thing in the MCU. According to the theory, the location of each Infinity Stone corresponds to a letter in Thanos' name. The Space Stone was in the Tesseract; the Reality Stone is the Aether; the Time Stone is held in a Necklace; the Power Stone was locked in the Orb; and the Mind Stone rested in a Scepter. If that's a coincidence, it's a pretty awesome one and only the "Necklace" part is reaching. That still leaves the "H," which some think refers to Heimdall or the Heart-Shaped Herb. Others think it could stand for Heart, and that Thanos will have to kill something he loves to acquire the Soul Stone. That's a big leap right there, but fun nonetheless.
Tony Stark Is The Soul Stone
This one gets put into the whacky file. There is one theory that postulates that Tony Stark himself is the final Soul Stone, mostly because of one particular promotional one-sheet. The poster depicts each stone with a character it's associated with, i.e. Captain America and the Space Stone, and Vision and the Mind Stone. Iron Man happens to be with the Soul Stone, which has led people to theorize he is somehow related to the missing stone. As to how Tony could be the Soul Stone or how any of that makes sense, well, there's nothing great backing it up. But I don't think people are entirely wrong for thinking Iron Man is associated with the Soul Stone. We know next to nothing about his journey in the movie, so he could very well be on the hunt for the stone.
Adam Warlock Has It
In the comics, Adam Warlock is the one who possesses the Soul Stone and he's the one who unites the heroes of Earth in a plan to steal the Infinity Gauntlet from Thanos. One can understand how comic book fans would think that something similar could happen in the movie, especially after he was teased at the end of Guardians of the Galaxy Vol. 2. However, James Gunn has all but come out and said that Adam Warlock doesn't have the Soul Stone and there's been no indication that he's in the movie. Warlock's role has kind of been given to the Vision and Infinity War is already jam-packed with enough characters as it is. Adam likely has a big part to play in the future of the MCU, but who can say when that future begins.
Thanos Already Has It/It's Not In The Movie
I'm piling these two together because they are both equally kind of a bummer. The first theory is that the reason we haven't seen the stone is that Thanos already has it. That would certainly save time in a movie that's two and a half hours long, but it's also not exciting at all. The latter is something that I'm more accepting of, but after all this build-up, it would be disappointing to not see the Soul Stone. It really all depends on what the game plan is for Avengers 4, but obviously, that plot's been kept under lock and key.