- "Soul holds a special place among the Infinity Stones. You might say, it is a certain wisdom."
"Tell me what it needs."
"To ensure that whoever possesses it understands its power, the stone demands a sacrifice."
"In order to take the stone, you must lose that which you love. A soul for a soul."
- ―Red Skull and Thanos
The Soul Stone was one of the six Infinity Stones, the remnant of a singularity that predates the universe. For some time, it was kept on the planet Vormir under the watchful eye of the Red Skull, before Thanos came to the planet in search of it and had to tragically sacrifice his beloved daughter Gamora to obtain it.
In 2023, during the Avengers' Time Heist, two Avengers Black Widow and Hawkeye traveled to the year of 2014 to retrieve the Soul Stone on Vormir. Approached by the Red Skull and learning that one of them would have to be sacrificed in order to get the Stone, both Natasha Romanoff and Clint Barton were willing sacrifice themselves and not let the other die. So they both fought each other to make the sacrifice until they both ended up dangling from a cliff. In the end, Romanoff sacrificed herself so Barton can get the stone, reunite with his family, and let the other Avengers undo the Decimation.
- "There are relics that pre-date the universe itself. An ancient force of infinite destruction."
Guarded by Red SkullVormir where it became concealed in a shrine, accessible only to those who were willing to sacrifice someone that they loved. In 1945, the Space Stone banished the Red Skull to the planet after he had abused its power, due to knowing that the HYDRA commander would be unable to make the sacrifice required to obtain the Soul Stone. The Soul Stone then cursed Red Skull, transforming him into an immortal wraith with the power to immediately know whoever comes to Vormir and preventing him from leaving the planet. He eventually would go on to accept this fate, become a Stonekeeper and serving as an adviser to those who would seek the Soul Stone's power.
As Thanos began his quest for the Stones, he sent the Black Order to scout the locations of the artifacts. Gamora and Nebula eventually tracked the Soul Stone down to Vormir only to conceal its location from Thanos with Gamora burning the map that had led them to it, though not before she had memorized its location. Thanos easily deduced that Gamora had located the Soul Stone, which he later attributed to her poor skill in lying, but allowed her to believe she had fooled him for the time being.
Several years later, Thanos revealed to Gamora that he had never been fooled by her claims of never finding the Soul Stone and managed to force her to divulge the Soul Stone's location, via ruthlessly torturing Nebula, taking her with him to Vormir. As they neared the shrine, they were approached by the Red Skull who explained that Thanos had to sacrifice someone he loved in order to gain the Stone. Thanos then tearfully threw Gamora off of the cliff, her sacrifice allowing him to obtain the Stone.
Having successfully claimed the Soul Stone, Thanos returned to Titan, where he was confronted by an alliance of the Avengers, the Masters of the Mystic Arts and the Guardians of the Galaxy. When Doctor Strange cast a spell creating dozens of copies of himself in order to restrain him, Thanos used both the Soul Stone and the Power Stone to track down the real Strange and destroy the copies.
Thanos then headed to Wakanda, where he retrieved the Mind Stone from Vision. Although he was stabbed by a vengeful Thor, Thanos retained enough strength to complete his quest, activating the Infinity Gauntlet with all the Infinity Stones, including the Soul Stone, to wipe out half of all life in the universe. This act briefly sent his consciousness into the Soulworld, where he briefly communed with a reflection of Gamora in her child form, telling her that he had achieved his goal but solemnly admitting that fulfilling his destiny had cost him everything.
Following the Decimation, Thanos retreated to the utopian world of Titan II where, after three weeks, he turned the power of the Infinity Stones inward, destroying them. In 2023, the Avengers time travelled to collect past versions of the Infinity Stones and use them to undo the Decimation. In 2014, Hawkeye and Black Widow travelled to Vormir where the latter sacrificed herself to allow Clint to claim the stone. When Bruce Banner later enacted the Reversal of the Decimation, he attempted to resurrect Romanoff but was unable to owing to the rules of the Soul Stone. Captain America later returned the Soul Stone, along with the others, back to its proper place in time.
The Soul Stone ranks as possibly the most dangerous of all the Infinity Stones, with it holding a special standing among the others. Uniquely, in its shrine on Vormir, the Stone purposefully imposed a test to those who would try to claim it - only the sacrifice of a loved one to the Stone would allow for someone to wield it. The sacrifices for the Stone are permanent and irreversible, as not even the omnipotent combination of the Six Stones could resurrect them. The Soul Stone has the ability to manipulate the soul, the essence that makes up an individual, and has the ability to resurrect and conjure the spiritual representation of the people who are dead.
Upon Thanos acquiring it, the Titan uses it the least out of all the Stones but still displays familiarity with the Soul Stone's powers. During the Battle of Titan, when cornered by Doctor Strange's mirror images, Thanos activated the Soul Stone and combined it with the Power Stone to instantly destroy all the false images and reveal the real one while also briefly forcing Strange's astral form out of his body.
After the Infinity Gauntlet was completed, the Soul Stone was used in tandem with the five other Infinity Stones to wipe out half of all life in the universe with Thanos' decimation. The Soul Stone contains a pocket dimension, consisting entirely of shallow water underneath a dim orange sky, where the souls of the dead can be communicated with.
- In the comics, the orange-colored (previously green) Soul Gem gives the owner the power to alter and manipulate all souls. It also acts as a gateway to its own pocket dimension. When used in conjunction with the other gems, it gives the user complete control over all life in the universe.