Marvel's Eternals movie may reveal who actually came up with the rules for the Soul Stone, which were established in Avengers: Infinity War. The Soul Stone rules ultimately cost Gamora (Zoe Saldana) her life in Infinity War, and also led to one of Avengers: Endgame's two biggest deaths - Black Widow (Scarlet Johansson), who sacrificed herself instead of being sacrificed.
For years, the Soul Stone was one of the MCU's biggest mysteries. Gradually, Marvel Studios began to unveil the MCU's Infinity Stones, though for a while the true nature of some of the Stones were masked by disguises, like the Tesseract secretly being the Space Stone. Through Captain America: The First Avenger, The Avengers, Thor: The Dark World, Guardians of the Galaxy, and Doctor Strange, Marvel revealed the Space, Mind, Reality, Power, and Time Stones, respectively. So by 2016, Marvel had already given away what and where five of the six Infinity Stones were, but it wasn't until Avengers: Infinity War in 2018 that Marvel pieced together the whole puzzle.
Avengers: Infinity War did finally reveal the shocking truth about the Soul Stone and its connection to a villain who had long been forgotten by the heroes of the MCU, the Red Skull (now played by Ross Marquand). But, the last two Avengers movies left a few things ambiguous, such as the rules for the Soul Stone. Who made them, and why? Marvel's Eternals movie, which will dive deep into the rich history of the Marvel Cinematic Universe, may be the film that provides an answer to these questions. Here's who may have created them, and why they would have done it.
The Soul Stone Rules Explained
In Avengers: Infinity War, the search for the Infinity Stones brings Thanos (Josh Brolin) and Gamora to the planet Vormir, where Thanos expects to get his hands on the highly-coveted Soul Stone. There, they encounter a robed figure who viewers recognize as Captain America's former nemesis, the Red Skull. The Red Skull explains to Thanos and Gamora that his search for one of the Stones caused him to be "banished" to Vormir, forcing him to guide others to a "treasure" he can never take for himself.
According to the Red Skull, to possess the Soul Stone, one must give up what they love. The Skull says this is because the Stone demands this sacrifice so that the person who wields it can have a proper understanding of its power. Being willing to lose what you love is the key to acquiring the Stone, and the primary reason why the Red Skull could never have it. But unlike the Red Skull, Thanos is capable of love, so after killing his daughter, he is able to possess it, just as Hawkeye (Jeremy Renner) is able to claim it after Black Widow throws herself off the ledge in Endgame.
Marvel's Celestials Are Connected To The Infinity Stones
Who came up with these rules and how did the Red Skull know about them? Red Skull could have uncovered the rules while searching for the Stones on Earth, but as for who made the rules, this hasn't been delved into yet, but more could be learned about the Infinity Stones in Marvel's Eternals movie, which will deal with the Celestials. Viewers know from Guardians of the Galaxy that a member of the Celestials once carried an Infinity Stone. This Celestial, Eson the Searcher, wielded a staff that held the Power Stone and proceeded to destroy a planet with it. This confirms that these cosmic beings of supreme power have a prior connection to the Infinity Stones, but how deep that connection goes remains to be seen.
It's further hinted at in Avengers: Endgame when Nebula (Karen Gillan) talks about Vormir. She claims it's the "center of Celestial existence". Based on this comment, it appears that the Celestials have been to Vormir, or have lived there in the past. According to the Collector (Benicio del Toro) in Guardians of the Galaxy, the Infinity Stones could be wielded by the Celestials because they were powerful enough to use them, or at least temporarily. The Collector also mentions a "group" was able to share the power of the Stones, which could mean that six of the Celestials each had their own Stone.
The Celestials May Have Created The Soul Stone Rules
If the Celestials ever possessed the Infinity Stones, what could they have done with them? Before being destroyed by them, or being forced to give them up, the Celestials may have separated the Stones and found ways to keep them out of the wrong hands. If they possessed all six, it's possible that they used a combination of the Stones' power, and perhaps even their own abilities, to impose rules on the Stones. It could be that Celestials altered the Infinity Stones, specifically the Soul Stone. The Celestials, who would know how badly people would want the powers of Stones and would of course be fully aware of the destruction they could cause, could have taken measures to ensure that not just anyone could take the Stones.
In Red Skull's conversation with Thanos and Gamora, its implied that Red Skull believes these rules were created by the Stone itself when he says that it has a "certain wisdom". This would suggest that the Infinity Stones are sentient beings who actually have control over who possesses them, but instead, it may have been the Celestials who determined these things. Eternals could explore this idea, and it could explain why they would even want to make it possible for people other than themselves to wield the Stones.
In Marvel Comics, it's established that the Celestials - who created the Eternals and the Deviants - are scientists. They explicitly ordered the Eternals to stay out of human affairs. As scientists, the Celestials wanted to study all three races and see how they would develop, and what decisions they would make. Human civilization couldn't progress properly if the Eternals solved all their problems for them. This same logic could apply to their approach to the Infinity Stones, and this could even be mentioned in Eternals when the movie touches on the motives and actions of the Celestials. It seems possible that if the Celestials did indeed make the rules of the Soul Stone, they did so because of their own curiosity.
