Avengers: Infinity War belongs to the Marvel Cinematic Universe (MCU). This title was given to the story created to reunite all Marvel movies in the same “story complex” for the big screens. 18 movies have been released in this storyline, including all the Avengers-related movies, Black Panther, Spider-Man, Guardians of the Galaxy and Doctor Strange.
The franchise began in 2008 with Iron Man. However, to understand the plot behind The Avengers: Infinity War, one should be aware of the other many films released after the breakthrough from 2008 and understand that the Infinity Stones have been present in this universe from the beginning. To make things a bit more clear, we are going to help you out by explaining what these Stones are and why they are so important.
Why is the movie called Avengers: Infinity War?
Mostly because (hold on, this is not a spoiler) Thanos will come for the Infinity Stones (Infinity Gems in the comics). He is obsessed with them and, if you didn't notice, they are always popping up in the MCU. There are six stones in total and each one of them has a different power. Thanos’ plan is to reunite them into what is called the Infinity Gauntlet piece.
The Space Stone was introduced to us while still in the first Captain America movie (2011) in the form of the Tesseract. The gem allows interdimensional space travel and was present in several of the MCU films. It was last seen in Thor: Ragnarok (2017) and believed to have been stolen by Loki.
The reality gem was first seen on screens during Thor: The Dark World (2013). The Reality Stone, also called Aether, transforms matter into dark matter. It’s self-explanatory how dangerous this can be. The Aether was last time seen being delivered to the Collector, as “it is not wise to keep two Infinity Stones so close together” (considering the Space Stone is already in Asgard).
You might not have noticed at first, but that artefact found by Peter Quill AKA Star-Lord in the first Guardians of the Galaxy was the Power Gem. As explained by Gamora: “the stone reacts to anything organic, the bigger the target, the bigger the power surge”. After the Guardians defeat Ronan the Accuser, one of Thanos disciples, the Stone was taken to the Nova Vault on Xander. This was the last time we (as audience members) have seen the stone.
The Mind Gem makes it possible to control and influence minds as well as alter people's perceptions. Loki had the stone for a while. In Avengers: Age of Ultron (2015) Tony Stark decided to “connect” the Stone to his computer and gave life to Vision, an android created by Ultron, who now considers himself a mixture of Ultron and J.A.R.V.I.S (Tony Stark's personal assistant and computer). Vision has the Mind Stone in his forehead and was last seen During Captain America: Civil War (2016).
Whoever watched Doctor Strange (2016) saw the Time Stone in action. Also called the Eye of Agamotto in the film, this gem was in possession of the Masters of the Mystic Arts. Stephen Strange used it to manipulate time and save Earth.
We still haven’t seen the Soul Stone in the MCU yet, which leads us to think that this will happen during the Infinity War movies. The Soul Gem is possessed by Adam Warlock in the comics, “the perfect human”, and grants total control of reality and capture souls. The Stone itself is sentient.