Adam Warlock's shadow has been looming over the Marvel Cinematic Universe ever since James Gunn introduced the character in Guardians of the Galaxy 2. It is expected that Adam, who is a big part of the Infinity War comics, will have a large part to play in the future of the MCU, but will he be further introduced in Avengers: Endgame? A new theory suggests that he and Vision might have a pretty big role to play in the movie and how it sets up Phase 4 of the MCU.
Infinity War sees Vision go through quite a bit, but we also learned that he and the Mind Stone were evolving. Thanos and his Black Order are coming for the Infinity Stones and Vision wants to remove and destroy the Mind Stone, in an effort to keep Thanos from achieving his goal. While in Wakanda and deciding whether or not taking the stone out of his head will kill him, Bruce Banner explains that there's a good chance that Vision with survive. He explains.
"Your mind is made up of a complex construct of overlays. JARVIS, Ultron, Tony, me, the Stone. All of them mixed together, all of them learning from one another... if we take out the Stone, there's still a whole lot of Vision left. Perhaps the best parts."
With that being said, there have been more than a few theories that state Vision is taking on the Adam Warlock storyline for the MCU. However, this could also mean that Infinity Stones are able to be given to other characters to take on their soul, much like what Warlock did in the comics. Warlock has the Soul Stone embedded in his head and then collects the scattered stones to hand them out to the right souls, allowing them to, "lead their own individual lives. Write their own destinies."
This could mean that the Infinity Stones going forth after Avengers: Endgame are all living entities while bringing Adam Warlock into the MCU. There are some problems with this theory. For one, the Russo Brothers claim that Warlock will not be in Endgame because they don't want to do a direct adaptation of the comic book source material, which makes complete sense. However, a lot has changed, especially with Guardians of the Galaxy 3 being on hold.
Additionally, the Russo Brothers have been known to throw out some misdirects. For instance, Avengers: Endgame was guessed as the title pretty much right away, but the directing duo shot it down and said that the title was not uttered during Infinity War. Obviously, they couldn't come out and say that at the time, it would've blown the whole secret. They might be doing the same thing with Adam Warlock in Avengers: Endgame, we'll just have to wait and see. This fan theory was originally presented by Screen Rant.