There are six Infinity Stones in the Marvel Cinematic Universe. These ancient, all-powerful artifacts have been adapted rather faithfully from the pages of Marvel Comics where they were first introduced as "Soul Gems." It wasn't until the œMad Titan Thanos collected them that he renamed them with better suited individual descriptions of each.In the MCU, something similar is about to occur next summer in Avengers: Infinity War, the first of two Avengers movies that will bring together nearly all of the main characters in the franchise to close it out. Don't worry, the MCU isn't ending. Just the current iteration of it is coming to an end. Sort of. And the conclusion begins with Thanos (Josh Brolin) collecting the Infinity Stones which have been slowly introduced over a decade of films.

For the purposes of the movie franchise crafted by Marvel Studios, these gems are referred to as Infinity Stones and so far, five of the six have been introduced by the end of Thor: Ragnarok. What and where are they currently and where is the last one?

"Before creation itself, there were six singularities. Then the universe exploded into existence, and the remnants of these systems were forged into concentrated ingots... Infinity Stones."

•The Collector

1. The Space Stone (Tesseract)

Tesseract in Avengers

"Howard Stark fished that out of the ocean when he was looking for you. He thought what we think; the Tesseract could be the key to unlimited sustainable energy. That's something the world sorely needs."

•Nick Fury

The first Infinity Stone introduced in the MCU was the Space Stone although we didn't know it at the time. The Tesseract or œCosmic Cube was the first of these introduced in 2011's Captain America: The First Avenger. In an interesting connection to Thor lore (specifically, Yggdrasil and Asgard's interest in Earth), the Red Skull (Hugo Weaving) and his Hydra forces locate and take for themselves the Tesseract from Tønsberg in German-occupied Norway.

The Red Skull uses the Tesseract to power weapons for Hydra but by the end of the film, it's lost in the ocean until Howard Stark (father of Tony Stark a.k.a. Iron Man) recovers it. It reappears in 2012's Avengers as something S.H.I.E.L.D. is experimenting on in present day until Loki (Tom Hiddleston) steals it for Thanos, using it to start an invasion against Earth.

Loki fails and Thor (Chris Hemsworth) takes him and the Tesseract back to Asgard for safekeeping. The Tesseract remains in Odin's vault and is seen several times in Thor: Ragnarok, most notably at the end when Loki stops to take notice of it before beginning Ragnarok and the destruction of the realm.

We know from the unfinished Avengers: Infinity War teaser footage that Loki has the Tesseract so it's obvious he takes it for himself in Thor: Ragnarok and has it with him on the starship the survivors of Asgard are on by the end of the film. Of course, the film's mid-credits sequence depicts their ship confronting a much larger, ominous space vessel that we presume represents the forces of Thanos...

Loki Scepter Vision Forehead Mind Stone

2. The Mind Stone (Loki's Chitauri Scepter, Vision's Forehead)

Another bait and switch for audiences, the Mind Stone was introduced as Loki's Sceptre in The Avengers (2012). That weapon, which allowed Loki to mind control Hawkeye (Jeremy Renner), Dr. Erik Selvig (Stellan Skarsgård), and others for his cause, was given to him by Thanos. It wasn't until 2015's Avengers: Age of Ultron that we learned the Sceptre's blue crystal actually housed the yellow Mind Stone although this one was unsurprising.

Ultron (James Spader) takes Loki's Scepter from Avengers HQ (in New York's Stark Industries tower) and uses it to give life to what he hoped to be a new host android body, giving birth to the Avenger we know as Vision. The Mind Stone remains in the forehead of Vision and we know next year Thanos will take it from him, leaving the question of whether Vision can survive and function without it. We think Scarlet Witch's powers will be the solution to that imminent predicament so don't fret.

Why Thanos would give up an Infinity Stone to Loki in hopes of getting another one back remains an unanswered question. We'll save this conversation for another day but Thanos has so far done little else in his brief appearances but consistently fail to build up his collection of Infinity Stones. He seems to be the opposite of a master tactician. Avengers: Infinity War has much to do in 2018 to turn that around and justify Thanos' role as the œbig bad villain of the MCU.

3. The Reality Stone (Aether)

Aether in Thor the Dark World

"Their leader, Malekith, made a weapon out of that darkness and it was called the Aether. While the other relics often appear as stones, the Aether is fluid and everchanging. It changes matter into dark matter. It seeks out host bodies, drawing strength from their life-force."

•Odin

The Reality Stone first makes its appearance in the prologue of Thor: The Dark World, the second film of Marvel Phase 2. It's shown to be a powerful substance referred to as the Aether and unlike the other Infinity Stones, it's not in the form of solid. Malekith (Christopher Eccleston), leader of the Dark Elves, aimed to use it to alter the entire universe into a dark state 5000 years ago but was thwarted by an Asgardian army led by Bor (Odin's father).

Bor, knowing the dangers of Infinity Stones, ordered the Aether hidden away until the present day events of Thor: The Dark World unfolded. See, every 5000 years, the nine realms (Asgard and Earth representing two of them) would align in an event dubbed the "Convergence" which created passageways (portals) between all the realms and Malekith wanted to use this to spread his darkness (whatever that means) across them all. Because the next Convergence was happening in present day, Jane Foster (Natalie Portman) conveniently found herself pulled through a portal to precisely where the Aether was hidden and it used her as a host.

After some battles and portal hopping, Thor and friends save the day yet again and defeat Malekith. We learn that since Asgard already has an Infinity Stone in Odin's vault, in order to protect the universe they wish to keep them separate and so Volstagg (Ray Stevenson) and Lady Sif (Jaimie Alexander) are sent to deliver the Aether to The Collector for safekeeping where it currently remains. The Collector, like several other major players in the galaxy, aims to collect them all for himself (he also sought out the Power Stone the following year in Guardians of the Galaxy as we'll discuss next).

We don't know exactly why the Aether was given to The Collector (real name: Taneleer Tivan). It was either Loki's doing (while impersonating Odin) because he knows the dangers of Infinity Stones after meeting Thanos (the same way Gamora came to realize this in Guardians of the Galaxy) or it could be Heimdall (Idris Elba) sending it to what he saw as the safest place which plays nicely into the idea of him banished by Odin (Loki) by the time we see him in Thor: Ragnarok.

Power Stone in Guardians of the Galaxy

4. The Power Stone (Orb)

The plot MacGuffin of 2014's Guardians of the Galaxy was a mysterious orb multiple parties are seeking. From Ronan the Accuser (Lee Pace) and Thanos to The Collector and The Broker, even the heroes (Gamora, Star-Lord, and Yondu) battle amongst themselves for the orb which we learn throughout the film is actually a shell housing the purple Power Stone - an ingot so powerful it can destroy a world with just a touch.

The Guardians of the Galaxy rally together, with the help of the Ravagers and Nova Corps forces, to prevent Ronan from using the stone against the planet Xandar and decide to do the right thing by giving the Power Stone to the Nova Corps for protection. It remains at Nova HQ on the planet Xandar.

Related: Marvel's Phase 4 Launches A New Movie Saga

This means Thanos and/or his forces will likely attack Xandar in Avengers: Infinity War, and assuming they succeed, could lay waste to the planet and Nova Corps which would offer the needed setup for Marvel Studios introducing the superhero we know as Nova from the comics - a character that Guardians of the Galaxy writer-director James Gunn revealed was considered for Marvel Phase 4.

5. The Time Stone

The Eye of Agamotto in the MCU

2016's Doctor Strange introduces the Eye of Agamotto and with it, the secretive world of magic and mysticism. Sanctum Sanctorums around Earth protect it from supernatural threats and this mysterious faction of sorcerers was founded by Agamotto who's yet to be explained in the films. Along with Agamotto's teachings he left behind an artifact housing the Time Infinity Stone, meaning there were not one, but at least two Stones already here on Earth for a lengthy period of time (the other being the Tesseract).

The question of why the Stones keep finding there way to Earth and what makes our planet (known as œTerra throughout the galaxy or Midgard across the Nine Realms) remains one of the biggest unanswered mysteries of the MCU.

By the end of Doctor Strange, Stephen Strange has become the new Sorcerer Supreme and he leaves the Eye of Agamotto where it was housed all along, but can still access it whenever he needs. This artifact provides Marvel with arguably the most interesting plot device to use in Avengers: Infinity War the untitled Avengers 4 as it wraps up the MCU as we know it. Expect there to be some time-travel!

6. The Soul Stone

Most theories leading up to Thor: Ragnarok had positioned it as the most likely story for the Soul Stone, the final Infinity Stone, to be introduced. Theories of where it is ranged from Heimdall or Odin having it all along, using it as the source of their unique individual powers, or the Goddess of Death, Hela, having it, but these were all wrong.

The Soul Stone is not in Thor: Ragnarok, leaving only two movies left for it to be introduced. Our money is on the Soul Stone being introduced in Black Panther and we explore the reasons why here. It boils down to Black Panther's secretive and highly advanced nation of Wakanda having access to Vibranium which came from a meteor and also embracing spiritually in such a way where Black Panther also reigns over Necropolis, the City of the Dead. The Soul Stone being attached to the extraterrestrial source of power and the Black Panthers being able to commune and draw power from their ancestors seems perfectly connected for what the Soul Stone can do.

However, this would mean three of the six Infinity Stones were already here on Earth, bringing us back to the big question of how and why this could be.

Soon, these stones will all be located and recovered as Thanos seeks to prove himself to audiences why he's the ultimate villain that 22 movies built towards. Share your thoughts and theories in the comments!

More: Thor: Ragnarok Post-Credits Scenes Explained

In Marvel Studios' Thor: Ragnarok, Thor is imprisoned on the other side of the universe without his mighty hammer and finds himself in a race against time to get back to Asgard to stop Ragnarok”the destruction of his homeworld and the end of Asgardian civilization”at the hands of an all-powerful new threat, the ruthless Hela. But first he must survive a deadly gladiatorial contest that pits him against his former ally and fellow Avenger”the Incredible Hulk!

Thor: Ragnarok is directed by Taika Waititi and returns Chris Hemsworth starring as Thor and Tom Hiddleston reprising his role as Loki. They are joined by Cate Blanchett, Idris Elba, Jeff Goldblum, Tessa Thompson and Karl Urban, with Mark Ruffalo and Anthony Hopkins. Kevin Feige is producing with Louis D'Esposito, Victoria Alonso, Brad Winderbaum, Thomas M. Hammel and Stan Lee serving as executive producers. Eric Pearson and Craig Kyle & Christopher L. Yost wrote the screenplay.

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