Avengers: Infinity War is the culmination of eighteen movies, and ten years of storytelling, a lot of which has centred on subtly introducing Thanos and the Infinity Stones. In the MCU we still don’t know a great deal about Thanos the ‘mad titan’, other than him being after the Infinity Stones. The stones themselves are powerful objects in their own right, that allow control over things such as time, reality, and people’s souls, but when all six stones are combined they turn the user into an all powerful god, allowing them to do literally anything they want.
Going into Infinity War, we know that Thanos intends to use the stones in his eventual bad guy ‘destroying the universe’ plan, but before that he needs to collect them all, and although we’ve seen almost all in once place or another through the MCU over the past ten years, they all have different stories and are all currently in very different places.
The Space Stone:
The blue Space Stone allows the user to manipulate the laws of physics, transporting themselves, others or objects across space. In the MCU it gives off energy that disintegrates people (when weaponised) and has shown up a number of times as ‘The Tesseract’. The first time we see the Tesseract is in the post credits scene of the first Thor movie, where Nick Fury shows it to Dr Erik Selvig promising it as the key to unlocking unlimited energy.
The Tesseract then appears fully in Captain America: The First Avenger (which is chronologically around seventy years before the end credits scene in Thor), where it features as the power source for the Red Skull and HYDRA’s weapons. Towards the end of the movie the cube transports the Red Skull away into space (which is in fact the lat time we saw him), and is then found by Howard Stark, who presumably keeps it safe within S.H.I.E.L.D until the events of The Avengers.
The Tesseract then has it’s biggest outing in 2012’s The Avengers, with Loki arriving on Earth (with the Mind Stone powered sceptre) searching for the Tesseract, eventually using it to unleash the Chitauri on New York. Throughout the movie we learn that Loki has been sent to Earth to retrieve the Space Stone by Thanos himself, who we only get glimpses of until the mid-credits scene, finally confirming that the Mad Titan is actively hunting the Infinity Stones in the MCU (a whole six years before we’ll properly see him in Avengers: Infinity War).
After the Avengers defeat Loki and the Chitauri in the battle of New York,Thor returns both Loki and the Tesseract to Asgard (where, according to the Red Skull in the first Captain America movie, the Tesseract was once held) and we don’t see the mystical blue cube on screen for the next five years, until Thor: Ragnarok.
In Ragnarok, the Tesseract shows up in multiple scene within Odin’s Vault, with both Hella and Loki giving the Tesseract some significant attention. Hella’s scene was also used to dub the Infinity Gauntlet in the vault as fake, correcting what was simply meant to be an easter egg in the original Thor movie.
The last time we see it Loki was looking longingly at the cube, and it was somewhat implied that he would (or at least could) take it. The Infinity War trailers fully confirm this idea, showing the god of mischief holding the cube, and handing it to someone. Given that the credits scene of Ragnarock shows the surviving Asgardian’s captured by Thanos, it looks like Loki might not of gotten very far before delivering it straight to Thanos, finally fulfilling, albeit most likely unintentionally, the deal he made with Thanos in The Avenger’s.
The Mind Stone:
The next stone is the yellow Mind Stone, that gives the user considerable physic abilities, including reading people’s thought and manipulating their behaviour. We first see the stone in action (although we don’t actually know it at that point) in the first Avengers movie as the power source for Loki’s mind controlling sceptre. Giving off a blue glow similar to the Tesseract all we know about the Sceptre at that point is that Thanos gave it to Loki to help him retrieve the Tesseract.
Following the first Avengers movie the Sceptre went missing, and we find out that Baron Von Strucker (of HYDRA) uses the sceptre to create a number of ‘enhanced’ beings, the only two survivors of his experiments being Wanda and Pietro Maximoff, a.k.a Scarlet With and Quicksilver.
By the time of Avengers: Age of Ultron the Avengers have been chasing the sceptre for a number of months, and the movie opens with them finally getting it back. Before Thor takes it back to Odin’s vault on Asgard, Tony decides to do some meddling in an attempt to create ‘Ultron’ a peace keeping Artificial Intelligence that would make the Avengers redundant. Unfortunately for them (and pretty much the entire world) Ultron becomes a crazed AI that goes all terminator and decides the best way to save the human race is to destroy it.
Ultron then tries to make himself a more physical body, and releases the Mind Stone from Loki’s sceptre, soon enough (thanks to the intervention of the Avengers, and Thor’s vision which showed him all of the Infinity Stones) they manage to stop Ultron, and instead use the body he created to make Vision. This MCU version of Vision is essentially a Virbanium built body, that behaves organically, combined with Tony Stark’s JARVIS AI, and then powered by the Mind Stone. Vision is extremely powerful, and ‘worthy’ given that he can wield Thor’s Hammer.
Vision and the Mind Stone next appear in Captain America: Civil War, where he explains to Scarlet Witch that he doesn’t know what the stone is, and that one day he hopes to control it rather than it control him. Not long after this Scarlet Witch manipulates the stone with her abilities and is able to sort of control Vision. The trailers for Infinity War show Thanos with a fully complete Infinity Gauntlet, so how exactly (if at all) Vision could function without the Mind Stone is so far unclear, but being one of the two stones we definitely know is on earth will be a large part of what brings him here.
The Reality Stone:
The red Reality Stone allows the user to alter reality, and has only shown up in one film so far; Thor: The Dark World. The Reality Stone appears as the ‘Aether’, a dark red almost liquid-like substance that the villains of the second Thor movie, the Dark Elves, intend to harness, returning the universe to ‘dark’.
The Dark Elves’ plan begins millennia ago, but after being defeated by King Bor (Thor’s grandfather) they retreat, eventually returning in (or at least around) 2013, to combine the power of the Aether with the latest convergence (the convergence being where the nine realms of the universe align and the barriers between them are at their weakest).
After Thor defeats Malekith, the leader of the Dark Elves, he sends Lady Sif and Volstagg to the Collector (in Thor: The Dark World’s mid-credits scene), who explain that they already have the Tesseract on Asgard and that is too dangerous to keep two Infinity Stones together. As they leave the Collector with the Reality Stone, he ominously says “one down, five to go”.
The Power Stone:
Allowing the user to increase their own strength and power, as well as boosting the levels of the other five stones, the purple power stone features as the Orb in Guardians of the Galaxy. The first Guardians movie shows Peter Quill taking the the Orb (in a very Indiana Jones-esque sequence) from the planet Morag. The rest of the film see’s the Guardians attempt to keep the Orb from the Kree fanatic Ronan, who in turn has made a deal to give it to Thanos (in exchange for Thanos destroying the planet Xandar).
The Guardians find out how powerful the Orb is from the Collector, and that it is in fact an Infinity Stone, unfortunately for them right after they find out Ronan arrives and manages to take the Orb. Ronan then turns on Thanos, intending to use the Power Stone to destroy Xandar himself.
Eventually (through some clever plans, awesome music, a dance off, and I Am Groot) the Guardians get the stone back from Ronan, harnessing the power (which no mortals should be able to do) in the process. The movie ends with Nova Prime (the leader of Xandar) locking away the Power Stone on Xandar.
The Time Stone:
The green Time Stone is currently held within the Eye of Agamotto, which grants powerful sorcerers the ability to manipulate time. We first see the Time Stone in Doctor Strange, where it was hidden in the Sanctum of Kamar-Taj. Stephen Strange discovers the eye whilst studying to become a sorcerer, eventually harnessing it to defeat Dormammu.
At the end of the movie stage places the Eye back where he found it, with Wong expiating that he will wield it eventually, but before then it’s “best not to walk the streets with an Infinity Stone”. The next time we see it is during Doctor Strange’s cameo in Thor: Ragnarock, where not only does the Sorcerer Supreme show a considerable control over his powers, but also wears the Eye, presumably meaning he has mastered his abilities and can now weird it properly. Again in the trailer we’ve seen it’s clear Thanos at one point gets all of the stones, and so him taking on the Sorcerer Supreme is something we definitely know is coming.
The Soul Stone:
Of the six Infinity Stones, the only we one we haven’t seen at all is the Soul Stone. The Orange stone controls both living and dead souls, eventually allowing the wilder to control life and death itself on a whim. We can see that Thanos gets it at some point, and I wouldn’t be surprised if the movie opens with him acquiring it first, or even getting it from the collector (who we already know has the Reality Stone, and very nearly got the Power Stone too).
With the Infinity War sequel still not having a title and director duo the Russo brothers teasing that fans should be ‘scared’ as to what it is, the end of Marvel’s Phase 3 is leading into a huge unknown, but with Thanos sure to utilise the full power of the stones once he has them all, meaning he is being able to time travel, alter reality, and bring back the dead, there is literally no end to what he can do.