Reality Stone

"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 to Thor and Jane Foster

The Reality Stone, also known as the Aether (pronounced ēTHər), is an Infinity Stone, the remnant of a singularity that predates the universe. A force of ancient and catastrophic power, the has the potential to transform the entire universe. This "stone" is unique since it has been liquified into a form of a dark red, viscous liquid. It was located in the Collector's Museum until Thanos stole it from the Collector.

Origin
"Long before the birth of light there was darkness, and from that darkness came the Dark Elves. Millennia ago the most ruthless of their kind, Malekith, sought to transform our universe back into one of eternal night. Such evil was possible through the power of the Aether, an ancient force of infinite destruction."

- Odin

The Aether is a remnant of one of the six singularities which existed before the universe. After the universe came into existence, four cosmic beings known as the Cosmic Entities forged the energies of these singularities into six immensely powerful objects called the Infinity Stones. The represents reality, as it possesses the power to bend the very laws of reality and physics, converting matter into dark matter. It is unique in that it has been liquified in the form of a flowing liquid or mist.

The First Attempt
"Sire, the Aether. Shall we destroy it?" "If only we could, but its power is too great. Bury it deep. Somewhere no one will ever find it."

- An Einherjar soldier and Bor

The Aether was used by the Dark Elves of Svartalfheim, in particular, by their leader Malekith. Every five-thousand years, the Convergence causes the Nine Realms to become aligned. In 2988 B.C., Malekith planned to use this event to release the and plunge the nine realms into eternal darkness; however, the Asgardians intervened and took the Aether from the Dark Elves by force, watching as the race was apparently decimated in battle. Bor then had the hidden away where no one could find it, and over the following five millennia, its story faded from known history.

The Second Attempt
"The Aether cannot be destroyed!" "But you can."

- Malekith and Thor

In 2013, near the beginning of the Convergence, a portal opened up to where the Aether was located; Jane Foster happened to walk through this portal and, through curiosity, made contact with it, causing it to become active and infest Foster's body, using her as a host. After arriving back on Earth, Foster exhibited an immensely powerful energy projection when being touched on the arm, and was taken to Asgard by Thor where the was discovered by Odin. During this time, Malekith sensed the 's activity and attempted to retrieve it by attacking Asgard. In the end, through the sacrifice of Frigga, Malekith and his army left before he could obtain the Aether.

Later though, when access to the Bifrost Bridge had been restricted, Thor, with a dying Foster, got Loki to take them through a hidden passageway to Svartalfheim. After getting there, they confronted Malekith and through various circumstances, the Dark Elf drew the Aether from Foster and into himself and left the planet. Both parties then arrived on Earth, where Malekith used the to battle Thor across worlds during the Convergence, which resulted in Malekith's destruction. Afterward, the Asgardians were able to contain the Aether, which was later given to the Collector for safekeeping, not knowing the true intentions the Collector had.

A Vision
Thor had a vision of the Infinity Stones and their role in the events of the previous years, the included. It is revealed that the Aether can indeed take the shape of an Infinity Stone rather then being just a liquid form.

Wielded by Thanos
"Reality is often disappointing. That is, it was. Now, reality can be whatever I want."

- Thanos to Gamora

Years later, Thanos arrived to Knowhere and took the Reality Stone from the Collector.

Capabilities

 * Reality Manipulation - The user with the can manipulate reality. During the convergence, this is manifested mostly through energy projections by both Jane and Malekith. Thanos used it primarily to create illusions (such as the one that hid the destroyed Collector's Museum from the Guardians of the Galaxy, or another that showed to Doctor Strange how Titan was in Thanos’s prime), or prevent lethal attacks, with both Peter's beams and Gamora's dagger being turned into bubbles, and the Hulkbuster being embedded inside a cliff wall. Because of its incredible powers, the Reality Stone is known as the most powerful out of the Infinity Stones.
 * Telekinesis - The user can manipulate objects when they have the . Thanos moved a moon of Titan in order to hit his targets perfectly, before crumbling in using the Power Stone, and sending the debris using the and a Space Stone-created portal.
 * Biokinesis - It is shown that the manipulation of reality includes changing how biological bodies behave. Example is Thanos turning Drax into pieces, or Mantis turned into strips. Both are reversed once he leaves.

Energy
"What I could do with the power that flows through those veins." "It would consume you."

- Loki and Thor

The converts matter to dark matter, and seeks out host bodies in order to draw strength from their life force, i.e., energy from living organisms, thereby sapping them of energy in a process that would inevitably prove fatal. As used by Malekith, the only one who fully understood its capabilities, it was capable of creating tendrils of itself or spikes to strike out at opponents, regenerate lost limbs, and create a tornado of energy. Whilst bonded to a strong host like Malekith, the greatly enhanced his physical strength and durability thereby allowing him to fight Thor on a reasonably even basis. On its own, the is capable of sending out shockwaves filled with its energy and pulses of power that can throw back any who it deems a threat to itself. These blasts have been enough to easily stun beings as physically powerful as Asgardians. The Dark Elves and Malekith appeared to have a connection to in that it awoke them from hibernation when the was used again and Malekith could sense the 's location.

Trivia

 * In the comics, the Collector owned the Reality Gem before Thanos took it from him.
 * Marvel Studios president Kevin Feige has confirmed that the Aether is the "Reality" Stone of the Infinity Stones.
 * The large structure which contained the is called the Chamber.
 * In comics, the Reality Stone is by far the most powerful of the Stones.