Reality Stone

"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."

- Einherjar and Bor

The Aether (pronounced ēTHər) is a powerful, extraterrestrial substance that has existed since before the universe began. A force of ancient and catastrophic power, the Aether is capable of destroying entire planets. Malekith, leader of the Dark Elves, attempted to use the Aether for this exact purpose. The Aether is one of the Infinity Stones. This "stone" is unique since it is in the form of a dark, red, viscous liquid, rather than a literal stone, like the other five. It is currently located in the Collector's Museum.

The first try
The Aether is one of the six Infinity Stones, unique in that instead of taking the form of a stone or solid object, it appears in the form of a flowing liquid or mist. The Aether was used prominently by the Dark Elves of Svartalfheim, in particular, the sorcerer Malekith. Every five-thousand years, a cosmic event called the Convergence causes the Nine Realms to become aligned, and in 2987 BC, Malekith planned to use this event and release the Aether to destroy the Nine Realms. 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 Aether hidden away where none could find it, and over the following five millennia, its story faded from known history.

The second try
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 Jane's body, using her as a sort of host. After arriving back on Earth, Jane exhibited an immensely powerful energy projection just by being touched on the arm, and was taken to Asgard by a concerned Thor where the Aether was discovered by Odin. During this time, Malekith had sensed the Aether'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 Jane, got Loki to get them through a hidden passageway to Svartalfheim. After getting there, they confronted Malekith and through various circumstances, he drew the Aether out of Jane and into himself and left the planet. Both parties then arrive on Earth, where Malekith uses the Aether to battle Thor across worlds during the Convergence until eventually Malekith is killed. Afterward, the Asgardians were able to contain the Aether in a hand-held container, which was later given to the Collector for safe keeping.

Aether Energy
"What I could do with the power that flows through those veins."

- Loki

The Aether converts matter to dark matter, and seeks out host bodies in order to draw strength from their life force 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 to strike out at opponents, or even regenerating lost limbs, along with creating a tornado of Aether energy. Whilst bonded to a strong host, Malekith, the Aether greatly enhanced his physical strength and durability thereby allowing to fight Thor on a reasonably even basis. On its own, the Aether is capable of sending out pulses of power that can throw back any who it deems a threat to itself. The Aether appeared to have a connection to Malekith and the Dark Elves in that it awoke them from hibernation and drew them to Asgard, as well as providing its human host with the ability to sense the former's presence.