One of the biggest mysteries yet to be solved in the Marvel Cinematic Universe is when and where fans will finally get to see the sixth and final Infinity Gem, the Soul Stone. Many thought that Black Panther would reveal where the Soul Stone is, since it's the last movie before Avengers: Infinity War hits theaters on May 4, but that never happened, so it seems we'll finally get to see it in Infinity War. A new promo poster for Infinity War showcases all of the Infinity Stones, which seems to offer a big hint at where the Soul Stone may be.

The poster features all of the Infinity Stones, with an image of the Marvel hero who is associated with each one embedded within the stone. The Space Gem image features Captain America (Chris Evans), since that gem debuted in Captain America: The First Avenger, the Power Stone photo features Guardians of the Galaxy's Star-Lord (Chris Pratt), the Time Stone features Doctor Strange (Benedict Cumberbatch), the Reality Stone features Thor (Chris Hemsworth) and the Mind Stone is with Vision (Paul Bettany). What's surprising is the Soul Stone prominently features Iron Man (Robert Downey Jr.), which could have some connection to the new Arc reactor in his chest, although that has not been confirmed.

The artwork comes from the upcoming IncrediBuilds: Marvel: Infinity Gauntlet Deluxe Book and Model Set, which will be released on April 17. Given how little we know about the Infinity War story thus far, it remains to be seen if Iron Man/Tony Stark will actually be connected to the Soul Stone, and if that connection has anything to do with Iron Man's new Arc reactor. It's possible that there may have been a connection to Tony Stark with the Soul Stone all along, but we won't know for sure until Avengers: Infinity War hits theaters on May 4.

The first five minutes of Avengers: Infinity War are said to be devastating, with theories abound that the opening of the movie may kill off a number of different heroes right off the bat. There has been no confirmation as to who may be killed off in the opening moments of Avengers: Infinity War, but with the arrival of Thanos (Josh Brolin), it could be anyone. As for the Infinity Stones, there are five that have already been introduced, and there is no indication of how many stones Thanos will actually get his hands on in Infinity War before Avengers 4.

This artwork debuted on Reddit, with some Redditors theorizing that Iron Man is the most important Marvel hero, so they put him on the Soul Stone artwork just because of that, and not because he has any connection to the Soul Stone. Regardless, we will likely get our first glimpse of the Soul Stone in Avengers: Infinity War, hitting theaters May 4, which will be followed by the final Phase 3 movie, Avengers 4 on May 3, 2019. Take a look at the new artwork below.

Infinity Stone Promo Art. from r/marvelstudios