Captain Marvel Theory:
March 8 marked the date of Captain Marvel’s debut in the Marvel Cinematic Universe. The heroine who can shoot off photon beams from her hands has been revealed to be the victim of the space stone. Maybe victim is the wrong term but it is clear that the powers of Captain Marvel in the Marvel Cinematic Universe are inexplicably linked to the Tesseract. The one responsible for granting Carol Danvers her powers is none other than Mar-Vell. And although the Marvel Cinematic Universe iteration of the character is wildly different from her comic counterpart, the intellect is still the same.
Although Captain Marvel provided the fandom with a set of whole new facts and even gave us a bunch of footage ahead of Avengers: Endgame, it established some mysteries that are yet to be substantially answered. One of these questions raised by the story of Captain Marvel is how in the world did Mar-Vell (Lawson) get a hold of the space stone in the first place when it was supposed to be in the custody of SHIELD scientists and operators.
Well, the prevailing theory is that Howard Stark had something to do with the unofficial back channeling of the Tesseract to Mar-Vell herself. There are two iterations of this theory and one of them have been posted by u/lvaztec on r/Fantheories. The same has been reproduced below for your scrutiny. Please read through it and also take a look at the top comment for an alternate version.
You see, Reddit believes that it was most likely Howard Stark who handed over the space stone to the Kree scientist. And as we know that Mar-Vell was working with the Skrulls it is also possible that Mar-Vell was trying to harness the energy of the Tesseract to aid the Skrulls in their endeavor against the Kree. It is completely possible that the Kree scientist found her way to earth in the search of the space stone and ended up crossing the path of SHIELD’s Howard Stark in her professional capacity.
Although both of the above iterations of the events are equally likely, it is hard to tell what actually went down before the events of Captain Marvel. And Marvel also makes it a point to leave certain things intentionally vague so they have freedom while writing future movies.
All of this is well and good but it does not change the fact that the space stone has now been a major plot point in more than four Marvel Cinematic Universe movies. The space stone has unparalleled power and it seems that entire civilizations are pursuing its power. The space stone has been a great source of conflict in the Marvel Cinematic Universe and continues to be one of the power sources for the Mad Titan. It seems that the space stone changing hands during the events of the Captain Marvel movie led to the Skrulls, Kree skirmish at the end of Captain Marvel, if not directly then indirectly.
The incidents of Captain Marvel are sure to have a great impact on the Avengers: Endgame, now even more so that we know that Captain Marvel aka Carol Danvers and the space stone are inexplicably linked. It is entirely possible that we will see this connection play a major role in the upcoming Avengers: Endgame. We may also get to see Carol Danvers take her ultimate energy form of ‘Binary’ by harnessing the power of the space stone during the events Avengers: Endgame.
Avengers: Endgame will hit the theaters worldwide on April 26, 2019. The cast is impeccable as some of the biggest names are part of the project including Robert Downey Jr. (Iron Man), Chris Evans (Captain America), Sebastian Stan (Winter soldier), Chris Pratt (Starlord), Chris Hemsworth (Thor), Idris Elba (Heimdall), Tom Hiddleston (Loki), Dave Bautista (Drax), Pom Klementieff (Mantis), Mark Ruffalo (Hulk), Scarlett Johansson (Black Widow), Samuel Jackson (Nick Fury), Cobie Smulders (Mariah Hill), Jeremy Reiner (Hawkeye), Benedict Wong (Wong), Benedict Cumberbatch (Dr. Strange), Tom Holland (Spiderman), Letitia Wright (Shuri), Chadwick Boseman (Black Panther), Paul Rudd (Ant-Man), Elizabeth Olsen (Scarlett Witch), Paul Bettany (Vision), Bradley Cooper (Rocket Raccoon), Vin Diesel (Groot), Zoe Saldana (Gamora), Karen Gillan (Nebula), Josh Brolin (Thanos).