The Mind Stone is one of the six Infinity Stones, the remnant of a singularity that predates the universe, which governed over the fabric of Mind. It was previously wielded by Loki inside his Scepter who received it as a gift from Thanos for the Chitauri Invasion. After the Battle of New York, the Scepter was confiscated by S.H.I.E.L.D., but it was later stolen by Wolfgang von Strucker's HYDRA cell whose scientists used it to give extraordinary powers to the twins Wanda and Pietro Maximoff using the power of the Stone. After the fall of HYDRA, the Scepter was recovered by the Avengers. It was taken by Ultron and its blue gem casing was shattered, releasing the inside it and was used to give life to Vision. It remained with Vision until it was forcibly removed by Thanos following the Battle on Wakanda, killing Vision in the process.
After the Universe came to be, the four immensely powerful Cosmic Entities forged the remnant of six singularities into concentrated ingots which were dubbed the Infinity Stones. The Mind Stone governed over the fabric of Mind.
The Mind Stone was originally portrayed as a containment vessel and a power source for the Scepter. The Infinity Stone granted the Scepter such diverse abilities to fire energy projectile blasts, manipulate minds, enable teleportation, perform astral projection and allow mental communication. The Infinity Stone has been under Thanos' possession unknowingly, who entrusted the Scepter to Loki of Asgard, along with an armada of Chitauri infantry troops and Leviathans, under the condition that Loki invade Earth to obtain the Tesseract and plan absolute subjugation under his reign. Upon arrival, Loki arrived on Earth via energy portal unwillingly emitted by the Tesseract, where he found himself arriving in the Joint Dark Energy Mission Facility in New Mexico. After arrival, Loki used the Scepter to defeat a unit of armed S.H.I.E.L.D. agents by shooting energy blasts and impaling them. Loki proceeded to use the Scepter's powers to brainwash S.H.I.E.L.D. agent Clint Barton and Astrophysicist Erik Selvig before escaping the facility on the verge to explode.
Loki continued to wield the Scepter to plot the oncoming invasion on Earth, where he used the staff to establish a mental communication to interact with The Other, and used his weapon during several altercations against the Avengers. After held captive and imprisoned on S.H.I.E.L.D.'s Helicarrier, the Scepter was transported at the laboratory station on board, where it was observed and studied by Tony Stark and Bruce Banner. During an heated argument between the Avengers and Nick Fury, the Scepter slowly affected their minds, increasing tensions and consequently, turning them against each other until an immediate threat finally put them back to concentration.
Escaping from his prison on the Helicarrier, Loki reclaimed the Scepter, which he later used his weapon to impale Agent Phil Coulson into his heart when Coulson attempted to confront him. He later attempted to use the Scepter to place Tony Stark under his control atop Stark Tower, however the Arc Reactor embedded in Tony's chest protected him. Loki continued to use the Scepter to fight against the Avengers in New York City after opening a portal for the Chitauri to invade Earth, until he lost it shortly after fighting his brother Thor. Near the end of the battle Black Widow picked up the Scepter and used it to activate a fail-safe that closed the portal being generated by the Tesseract. Following the invasion, Black Widow turned possession of the Scepter over to S.H.I.E.L.D.
In S.H.I.E.L.D.'s Possession
- "Could the connection between the Scepter and the Tesseract really be that simple?"
- ―Nicholas Cooper
The scepter was placed in the facility called S.H.I.E.L.D. S.T.A.T.I.O.N. to be researched by S.H.I.E.L.D. One of its researchers, Nicholas Cooper, was very enthusiastic about working with the scepter, but his colleague Mark Smith did not share his enthusiasm. Smith explained how he wanted to be a field agent, but as he was deemed psychologically unstable by Maria Hill, he was transferred to the science division.
Eventually, Smith's displacement with S.H.I.E.L.D.'s leadership allowed him to be recruited into HYDRA by Baron Wolfgang von Strucker. Strucker's first order to Smith was to retrieve the scepter.
While Cooper developed a new groundbreaking theory about the scepter's connection to the Tesseract, Smith, along with a HYDRA colleague, burst into the room and stole the Scepter while killing Cooper in the process.
In HYDRA's Possession
- "What we have is worth more than any of them ever knew. We've only scratched the surface and already..."
- ―Wolfgang von Strucker
The scepter was transported to the HYDRA Research Base in Sokovia, where Strucker and his scientists began to study it, and powered up a large number of Chitauri Guns using it. As Strucker was not completely satisfied with the results, he ordered his lead scientist Doctor List to gather volunteers among the rioting population of Sokovia for experiments with the scepter. Although many volunteers died as a result, the twins Pietro Maximoff and Wanda Maximoff gained extraordinary powers.
By the time of the Battle at the Triskelion, Strucker and his scientists realized that the Scepter's powers were far greater than they originally thought. In the meantime, Strucker and his scientists used their research into the gem inside the Scepter to start experimenting with artificial intelligence, for which they designed several very advanced robots.
Tony Stark and Bruce Banner both originally devised the idea for the Ultron Program as an extension of the Iron Legion to operate independently as an AI peacekeeping program and result total obsolescence of the Avengers. However, neither Banner nor Stark were capable to create the intelligence level of A.I. necessary to achieve this purpose on a large scale.
After the assault on the HYDRA Research Base, and the retrieval of the Scepter, Stark asked Thor if he could study it before Thor took it back to Asgard. Upon studying the Scepter, Stark and Banner found inside the Gem on the Scepter a net of neurons which could be configured into an artificial intelligence that could help finish the Ultron Program. At first Banner refused to help, but with a bit of persuasion he agreed. The two eventually configured a suitable AI structure and left J.A.R.V.I.S. to complete the work that would eventually led to the creation of Ultron.
In Ultron's Possession
The Mind Stone was revealed to be inside Loki's Scepter by Ultron, who used its power to enthrall Helen Cho, in order to make him a new body with a combination of her expertise using the Cradle and Ultron's supply of Vibranium. He later broke the Scepter to claim the jewel, so he could use its power to evolve into a perfect body.
Creating a Vision
Ultron's new body, with the Stone inside it, was taken when the Avengers stole the Cradle during the Battle of Seoul, leading to Tony Stark, Bruce Banner, and Thor granting the construct inside the Cradle life with the Stone embedded in its skull.
The Vision viewed Ultron as a danger to Earth and decided to join the Avengers in fighting him. During the Battle of Sokovia, Vision used the power of the Stone against the overwhelming army of Ultron Sentries, and combined its power with Iron Man and Thor's to overpower and defeat Ultron, who could not match Vision's strength. With the war won, Vision decided to join the Avengers and use his remarkable power to aid the protection of Earth.
Guarding and losing Scarlet Witch
- "I don't know what this is. Not really. I know it's not of this world, that it powered Loki's staff, gave you your abilities. But its true nature is a mystery and yet it is part of me."
"Are you afraid of it?"
"I wish to understand it. The more I do, the less it controls me. One day, who knows? I may even control it."
- ―Vision and Scarlet Witch
As the Avengers were now on the hunt for the Winter Soldier abroad, Wanda Maximoff and Vision stayed behind at the New Avengers Facility. Vision tried to make her comfortable, attempting to cook her a meal, which failed since Vision had never eaten anything before. The two discussed their abilities and how they viewed themselves, with Vision noting he did not fully understand the that gave him his power.
When the situation involving the Sokovia Accords aftermath got worse, Steve Rogers sent Clint Barton to rescue Wanda Maximoff from the New Avengers Facility. Barton set off an explosion outside to lure Vision out to investigate while he greeted his friend and explained the situation to her. On their way out, Hawkeye remained confident and noted that although he could not overpower Vision, there was somebody else who could. Much to Vision's horror, Wanda Maximoff then used her own powers to control the Stone and forced Vision to phase, making him free Hawkeye. Despite Vision trying to reason with her, Maximoff used her powers to slam Vision through the facility and deep underground, allowing Hawkeye and Scarlet Witch to then escape.
- "Captain Rogers, I know you believe what you are doing is right, but for the collective good you must surrender now."
- ―Vision to Captain America
Vision was the last of the Avengers to arrive at the airport on Iron Man's side as the teams clashed; when he arrived, Vision created a warning line by firing a beam from the Stone on his forehead in front of Captain America's team. He tried to talk and reason with Rogers to convince him to surrender, noting while Rogers believed he was doing the right thing by going against the Sokovia Accords, he should surrender.
Vision, seeing Captain America and the Winter Soldier try to escape to a Quinjet, became transparent, moving through Giant-Man, and used his Energy Blast from the Stone to bring down a watch tower, trying to cut off their escape. However, he discovered it was kept in the air due to the intervention of Scarlet Witch, who used her powers to stop it falling until War Machine used a sonic blast to subdue her, causing the tower to fall although Rogers and Barnes managed to escape.
War Machine asked for assistance to stop the Falcon, who was shooting at him to try and ensure that both Captain America and the Winter Soldier escaped safely. Distracted by talking with Scarlet Witch, Vision looked up and unleashed an Energy Blast aimed at Falcon, but Falcon saw the blast coming and moved out of the way and instead it struck War Machine directly in his amor's Arc Reactor, causing him to plummet to the ground.
Vision and Wanda Maximoff were attacked in Scotland by Corvus Glaive and Proxima Midnight, members of the Black Order and Thanos' adopted children. Glaive tried to steal the Stone from Vision's head, but Maximoff attacked him before he could succeed. The two were eventually rescued by Captain America, Black Widow and Falcon.
Realizing that Thanos is looking for the Mind Stone, the team, along with Bruce Banner and James Rhodes, traveled to Wakanda, where Shuri tried to remove the stone from Vision's head without killing him. However, before she could finish, she was attacked by Corvus Glaive. Vision managed to escape, but Thanos, who got all the other Infintiy Stones, came to the battle and tried to get the stone by himself. Vision soon realized that there is no other choice, and asked Maximoff to destroy the stone, knowing that it would kill him. As Thanos came for Vision, Maximoff realized she doesn't have a choice and destroyed the stone, killing Vision in the process. However, Thanos used the Time Stone to undo Vision's death and the Mind Stone's destruction. Once he did, Thanos grabbed Vision and tore the stone from his head before placing it on the Infinity Gauntlet, finally completing it. Even after Thor severely wounded him using all of his power and Stormbreaker, Thanos nevertheless managed to use the completed Gauntlet to wipe out half the universe with a snap of his fingers.
As the Infinity Stone that represents and governs the fabric of mind, the Mind Stone grants whoever holds it complete control over the hearts and minds of others. Like with all the other Infinity Stones, it is among the most powerful artifacts in all existence.
At its core, the Stone contains a highly advanced intelligence framework, akin to an incredibly powerful supercomputer operating similarly to a sentient mind. The Stone's intelligence is powerful enough to enhance and spontaneously grant sentience to the artificial beings Ultron and Vision. As implied by this intelligence, the Stone itself also possesses a form of sentience, with the Stone directly communicating with Vision in order to warn him of the coming threat of Thanos.
Contained within a Scepter capable of harnessing its power, the Mind Stone's power can dominate the minds of others on contact, placing them under the control of the wielder and loyal to their commands indefinitely. By placing the blade tip of the Scepter against a person’s heart, a blue, wisp-like energy is released from the Stone, which flows into the person’s body and spreads upwards to their head, turning their eyes a florescent blue color.
People put under the Stone's control will often regain their individuality after receiving a significant blow to the head, as with Hawkeye, since a temporary loss of consciousness will allow their normal mental state to "reset" and return. In some situations the effects of the mind control can be negated outright if the energy from the Stone is unable to diffuse into the target's body, such as when Tony Stark's Arc Reactor negated the energy instead.
The sentient and intelligent nature of the Stone also allowed it to operate independently of a host to a degree, allowing it to subtly compel and manipulate minds without the presence of a wielder. While being kept aboard the Helicarrier by the Avengers, the Scepter managed to compel the heroes to slowly turn against one another in a heated argument, escalating to the point where the Stone's power compelled Bruce Banner to pick up the Scepter involuntarily in an aggressive gesture.
The Mind Stone is also able to project the consciousness of its wielder, in order to mentally view and communicate with beings in faraway places. This ability is powerful enough to reach the far depths of outer space, as evidenced when Loki used the Scepter to communicate with the Other in Sanctuary. During this conversation, The Other was able to interact with Loki's projection and cause him pain in his physical body.
The Stone is also capable of granting great knowledge and greatly increasing the intelligence of whoever it is used on, as it "opened the eyes" of Clint Barton and Erik Selvig, showing them visions and granting them special knowledge they can use. Barton was shown targets and detailed plans for breaking into installations, and Selvig was shown visions of other dimensions and advanced knowledge of the science of the universe.
Notably, the Stone appears to also grant the ability to directly manipulate physical matter to an extent. Loki was able to directly alter the Scepter's physical form, allowing him to shape-shift it from its normal short, bladed and curved form, into either a portable cane-like form, or an elongated battle-spear taller than a human. Loki was also able to materialise and dematerialise his battle armor from thin air, in a manner distinct from his conventional illusions. Under the control of Vision, the Stone granted him unparalleled control over his own Vibranium physiology, with the ability to shape-shift his form and manipulate his own density. Vision was also able to utilise the Stone's computing power and intelligence to directly hack computers, powerful enough to burn Ultron out of the Internet. 
Conventionally, the Mind Stone is also able to simply unleash its pure energy in blasts or targeted beams for offensive and destructive purposes, as seen by how it was used by both Loki and Vision. The Stone's energy, through a potentially lethal process, is also able to enhance lesser beings with powerful abilities. While in HYDRA's possession, lethal experimentation by Wolfgang von Strucker managed to greatly enhance twins Wanda and Pietro Maximoff with the Stone's energy. Pietro's physical body was greatly improved, granting him incredible speed and reflexes, while Wanda was enhanced mentally, receiving powerful telekinetic abilities. It also likely enhanced Loki's strength, as while wielding it when it was contained inside the Scepter, Loki proved to be on par with Thor wielding Mjølnir in terms of strength.
The Stone itself is also nigh-indestructible by conventional methods, and wanton physical trauma to the Stone could also cause a potentially devastating release of its energy, to the point where Helen Cho warned that crashing the truck containing the Stone would potentially level the city of Seoul. Only an extremely powerful energy source similar to that of its own, such as the incredible powers granted to Wanda Maximoff, is capable of potentially destabilising its molecular integrity.
Contained inside the completed Infinity Gauntlet, the Mind Stone reaches its full potential and together with the other Infinity Stones upon the Gauntlet's completion, allowed Thanos to kill half of all life in the Universe with a simple finger snap even while severely wounded by Thor. The Mind Stone's specific role seems to be destroying the mind and heart of the victims. However, using all six Stones in this manner at such a weakened state caused the Stones's combined power to nearly overwhelm him and the Gauntlet as well as his left arm were left scorched by the release of energy.
- In the comics, the blue-colored (later yellow) Mind Gem gives the owner psionic powers like telepathy and telekinesis or can augment the pre-existing mental powers of its user. When used in conjunction with the other gems, it can link its user with all other minds in the universe at once. It was used by the Grandmaster, Thanos, Nebula, Adam Warlock, Moondragon, Magus, Rune, Primevil, Loki, Galactus, Professor X, Odeni, Hood, Ms. Marvel, Beast and Black Widow.