The Cosmic Cube is an item that can control matter and energy, answering to the will of the sentient beings that use them. They require practice to be used properly, but a skillful user can alter all reality to answer to its thoughts, granting anything they desire.
Most Cosmic Cubes are cube-shaped matrixes. However, similar objects with different shapes are known as Cosmic Containment Units.
Sentient beings wanting to create a Cosmic Cube must first generate a force field to open a rift to another dimension inhabited by the Beyonders, allowing the extra-dimensional energy to filter through the rift. When entering the Earth's dimension, the energies can be held in a matrix, and the force itself would shape the matrix into a perfect cube. It would also provide the Cube with its almost unlimited power.
The Cosmic Cube's primary ability is "wish granting" or rather an extreme level of reality warping. Originally thought to be powerful enough to affect reality on a multiversal scale, it turned out that most of its effects were probably illusory in nature. However, Doctor Doom still believes that the conquest of a universe is possible with one Cosmic Cube. In fact Thanos with the power of a Cube even became one with the universe and managed to defeat the entity Kronos. However, more recently a Cosmic Cube was able to effectively cause a multiversal chaos that threatened to destroy the whole omniverse, merging multiple realities in the process, which was confirmed as canon. The Cosmic Cube's power has also been shown to nullify the power of multiple cosmic beings simultaneously including the Stranger, Elders of the Universe and In-Betweener. Reed Richards even nullified Dr. Doom when he possessed the power of Galactus and proved able to restore Galactus to full power. The Cosmic Cube cannot affect souls and, given the Beyonder's inability to affect time, we can presume even the Cubes cannot affect time as the cubes possess only a fraction of the Beyonder dimension's power. The Cosmic Cube then easily rivals in application and scope the Infinity Gauntlet, which was multiversal before being retconned to universal level.
A Cube will eventually develop its own intelligence, commonly influenced by the beings who had manipulated it. Mephisto has postulated that the Cubes are hosts to a semi-sentient will and that, even in Cube form, they can choose how they want to be used and to deny certain wishes. Mephisto also has proposed that a billion-sentient universally-linked wills could overcome this problem and that the Cubes could be as powerful as the Infinity Gems.
Other types of Cosmic Cubes can be created by other means, but are extremely less powerful.
The Ringmaster had forged a Cosmic Ring with the power of a Cosmic Cube. He was defeated by a collection of heroes, ending with the Punisher shooting off his ring finger. Captain America was en route to delivering the ring to S.H.I.E.L.D. when a M.O.D.O.C. Squad attacked. His belt was damaged and the ring fell during the fight. The Cosmic Ring allows Curtis to warp reality within a 15 foot radius (4.6m) around him, giving him a 30-foot sphere of reality he can alter. Curtis Doyle was able to use the ring to create various objects such as ice cream and his costume, change his appearance, allow him to fly, grant himself superhuman strength and durability, and use the ring's power to counter his paralysis in order to allow him to walk.
Important Known Cosmic Cubes
First appearance: Tales of Suspense #79
The first Cosmic Cube created on Earth. A.I.M. managed to create a matrix of force fields which concentrated a flux of energy of the Beyonders and transformed it into a perfect cube with immense and vast powers: the Cosmic Cube.
Later it was revealed that this Cosmic Cube was a living being in embryonic form. Eventually, it developed its own consciousness, patterning it after the consciousness of the sentient being with whom it was in mental and physical contact. Finally, the Cosmic Cube would become a mature sentient being capable of independent will and action. Kubik was one such cube.
Red Skull's Cosmic Cube
First appearance: Super-Villain Team-Up #16
Years after the creation of A.I.M.'s Cosmic Cube, the Red Skull tried to re-create the powerful device. Using different slaves from his island, the Skull got enough mental power to create the Cube.
A.I.M.'s Second Cosmic Cube
First appearance: Avengers #386
A third terrestrial Cosmic Cube was created again by A.I.M. in the Boca Caliente island. The instability of the Cube caused its warping ability to leak out onto the surrounding island, creating versions of people anyone nearby thought of. The Avengers attempted to stop the Cube, and a dying Captain America was the one who willed it to do so.
Finally, an Adaptoid, which was accompanying the Captain, was impressed by the heroic nature of the Avenger and decided to transform itself into a non-sentient containment chamber for the cube's energies.
First appearance: Incredible Hulk #155
Thousands of years ago, the alien species Skrulls developed an artifact to modify reality following the wishes of the user. It was the first Cosmic Cube, apparently created by forming a meta-singularity or gray hole, which was really an opening to the Beyonders reality.
An X-Element from that universe crossed the gray hole and was trapped in a perfect force cube created by Skrull scientists. The Skrull emperor took the cube and declared himself a god. He reigned for many years but, unbeknownst to all, the Cube had potential to become a sentient being itself. Through the years of use, the emperor involuntarily printed some of his own traits in the embryonic consciousness of the Cube, thus the Cube began to develop his own personality. Since the Skrull emperor was a megalomaniac madman, the Cube also became a megalomaniac.
First appearance: Fantastic Four Annual #23
Kree Cosmic Cube
First appearance: Cosmos Cubed
A Cosmic Cube developed by the Kree. With an adequate power source, it was able to destroy anyone. When the Skrull tried to intercept the Kree courier and get the Cube, they accidentally landed in Ego. Uatu, the Watcher summoned a team of cosmic-level heroes to investigate.
That cube was used by the Super-Kree to power himself.
- Thirty different Cosmic Cubes gathered by Magus and Goddess in order to fuse them and create a Cosmic Egg.
- A malfunctioning Cube given to Mephisto by Thanos as a payment for his knowledge about the origins of the Cubes.
- A Cube part of twelve items the Avengers and the Justice League had to recover in a bet between the Grandmaster and Krona.
- A human-crafted less powerful Cube created by the U.S. Army which was stolen by Thanos' Zodiac. It was actually an advanced dark matter generator which was created using stolen A.I.M. formulas.
Cosmic Cube Fragments
Fragments of Cosmic Cubes have also been used:
- A.I.M. used a fragment of a Cosmic Cube along with Unstable Molecules to allow its creation, the Super-Adaptoid, to copy the powers of others.
- S.H.I.E.L.D. gathered various fragments from different Cosmic Cubes so the agency could manipulate reality when it deemed necessary. After the project was leaked to the public by the Whisperer, director Maria Hill pretended to shut the project down. S.H.I.E.L.D. continued experimenting on the Cosmic Cube fragments in secret. Then the fragments merged together into a single being, and this being transformed into a child. This child was named Kobik.
Ultimate Universe (Earth-1610)
An Ultimate Cosmic Cube first appeared when it fell to the home planet of Thanos. After discovering its power, Thanos attempted to control the whole of creation, but he was defeated, at the cost of numerous lives. After helping the group of alien super-soldiers Seed Nineteen to rescue one of their members, Tesseract from Thanos, the Fantastic Four encountered Thanos for the first time.
Thanos knew that Reed Richards would be able to construct the Cosmic Cube. Thanos first personally met Reed by possessing Ben Grimm and "requested" him to construct the cube with coercion by killing a weakened Johnny Storm. Fortunately Ben was able to resist Thanos' possession. Though Reed refused to build the Cube for Thanos, he did however intend to build it to use it against Thanos.
Eventually the Fantastic Four came into conflict with Thanos a second time in which he was able to harness Reed's Cosmic Cube and once again used it to express his will by conquering Earth and brainwashed Earth's heroes as his pawns to fight against his enemies. However, when Thanos attempts to utilize the Cube to ascend into godhood, he suddenly realized that there was something wrong and was instantly killed. It was elaborated that Reed had built a "cut-out" into the Cube so that the Cube would only respond to conscious, willed thoughts, and that he had removed this "cut-out" while Thanos was distracted and which allowed his death. With Thanos' death and the restoration of his past actions of utilizing the Cube, Reed disposed of the Cosmic Cube in a time-rift, accidentally landing on the home planet of a young Thanos, creating a paradox in which the present events were the cause of Thanos getting the Cube in the past. In this paradoxical move, the Cosmic Cube which Reed developed would be the original Cube that Thanos had discovered and nearly destroyed the universe with so long ago.
A second Cosmic Cube was built by A.I.M., who, months after the events of Ultimatum raided the abandoned Baxter Building and stole the blueprints of the Cube, while working along with the Red Skull, in order to remold the democratic society into their own version of the world. The Red Skull convinced other A.I.M. agents to betray an A.I.M. leader and get the Cube for their own purposes. S.H.I.E.L.D. gathered a new black ops unit called the Avengers in order to stop him.
The Skull easily overpowered the Avengers, but is ultimately defeated by his father, Captain America, who used a jet with teletransportation technology to stab his son. Before being killed by Wasp, Red Skull revealed that he wanted the Cube's power to alter reality and prevent the disappearance of his father in World War II, so they would be a happy family.
Marvel Cinematic Universe (Earth-199999)
After being retrieved by the Red Skull and Hydra during WWII, it was recovered by Howard Stark and subsequently kept under S.H.I.E.L.D. until the 21st century. During the period, it was used by infiltrated Kree scientist Mar-Vell to develop a engine capable of faster-than-light travel.
It was stolen by Loki in the name of Thanos, and it was used to open a portal and bring the invading forces of the Chitauri to Earth. However, S.H.I.E.L.D.'s newly formed team of superheroes called the Avengers defeated Loki and gave the Tesseract to Thor, Odin's son, to be kept in Asgard.
In Asgard, Heimdall used the Tesseract's power to restore the Bifrost. Later, when handing the Aether over to the Collector, Volstagg reveals that the Tesseract does indeed contain an Infinity Stone when he states that the two artifacts would be too dangerous to keep so close to each other. The Tesseract remained in Odin's Vault for five years, until Loki retrieved it while in the process of reviving Surtur to initiate Ragnarok.
The Tesseract is seen in two different timelines as the Avengers time travel to retrieve the Stones from the past: first, Scott Lang and Tony Stark tried to get the cube from Stark Tower after the Battle of New York, however it wound up out of Tony's hands due to the intervention of the past Hulk, resulting in Loki using it to escape. Knowing they still needed the Space Stone, Tony and Steve Rogers travelled further in time to 1970 to retrieve the Tesseract from a S.H.I.E.L.D. facility. 
The Avengers: Earth's Mightiest Heroes (Earth-8096)
In this reality, A.I.M. was hired by Hydra to create a powerful artifact. M.O.D.O.K. planned to use the Cosmic Cube project as a smoke screen to swindle money from Hydra. After the Cube was revealed to be a success, and a very powerful weapon, M.O.D.O.K. decided to return the money to Hydra, claiming that the Cube failed, in order to keep the Cube for himself. Hydra's leader Baron von Strucker realized A.I.M. was lying and started a war for its possession.
The Avengers were involved as Black Widow, who was a Hydra double agent, revealed to them the existence of the Cube. The clash ended when Captain America seized the cube simultaneously with Baron von Strucker, and nothing appeared to happen. But unknown to the heroes, the Cosmic Cube altered reality upon Captain America's desire, changing the path of his sidekick Bucky, to survive the explosion which originally killed him and caused the Captain to be trapped in ice for decades.
Marvel Disk Wars: The Avengers (Earth-14042)
In this reality, the equivalent of the Cosmic Cube is a spherical device called the Dimension Sphere.
It was first seen in the hands of Red Skull The Red Skull used the Dimension sphere to steal the biocodes of the Celebrity Five for himself and to give his team, the Masters of Evil, a major power-up so they could beat the Avengers. He also intended to use the Sphere for his ultimate plan to destroy the Earth. Through five devices called Gaia Anchors, The Red Skull wanted to unleash the Sphere's power directly into the Earth's Gaia Lines and corrupt them. After the Avengers thwarted this plan by destroying all five Gaia Anchors, The Red Skull used a fragment of the Dimension Sphere to turn Hikaru into his loyal servant. Finally, The Red Skull used the Dimension Sphere to power up his ultimate weapon, a giant robot. After the robot was defeated, the sphere was taken into S.H.I.E.L.D. custody.
Iron Man attempted to use the Dimension Sphere to create a device for accessing the Dark Dimension, where Dr. Akatsuki and Loki had been banished to earlier. The device worked, but when the portal opened, the villain Ronin came out and stole the Dimension Sphere for Loki. He continued to use the Sphere while leading the Celebrity Five in their mission to steal the Treasures of Darkness.
- In the Marvel Cinematic Universe, the Cosmic Cube is called the "Tesseract", and contains the Space Gem.
- 242 appearance(s) of Cosmic Cube
- 61 minor appearance(s) of Cosmic Cube
- 101 mention(s) of Cosmic Cube
- 97 image(s) of Cosmic Cube