Hey guys, its one of my recently made theories on the MCU, hope you like it. ^_^
So basically it rotates around the infinity stones and THE INFINITY WAR, and our main subjet is our own, most beloved TONY STARK.
We all saw HOWARD STARK meddling with the substance created by DR. ARNIM ZOLA in CAPTAIN AMERICA. And later on we even see him finding the TESSERACT, aka THE COSMIC CUBE. We also know that Howard Stark prepared instructions for his son to synthesise VIBRANIUM, which happens in IRON MAN 2.
So, what if DR. ZOLA made something like VIBRANIUM itself and so did TONY STARK. That means his ARC REACTOR runs on the technology of the INFINTY STONES. Another thing to notice was that in IRON MAN 2, the new ARC REACTOR is triangulal so is its VIBRANIUM core and the MARK 6 armor's unibeam projecter, while all the ARC REACTORS and projecters are circular. Our speculation is that VIBRANIUM and the TESSERACT are similar in nature, 4-dimensional to be exact. This could be the reason of the change in shape.
Moreover in the AVENGERS we see LOKI trying to pull off his mindcontrol magic on TONY with his sceptre but fails. We know the sceptre's power is similar to the cube. And by the fan's speculation(the movies can be entirely different) it is either powered by an INFINTY STONE(the TESSERACT) or is ont itself! The fans seem to think that it is the MIND STONE, capable of mindcontrol and maybe a crucial component in the AGE OF ULTRON. Anyways in the comics it is said that no INFINITY STONE can compete with another, and AVENGERS showed us just that. This might be the reason LOKI couldn't control STARK(and had perfomance issues).
So basically, if TONY has INFINITY STONE like stuff in his chest, he might be the key to the end of THE INFINITY WAR in the MCU.
Tell me what you think about my theory. :)
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Here's the INFINITY WAR trailer if you havent catched it yet.