Infinity Stones

The Infinity Stones were six immensely powerful gem-like objects tied to different aspects of the universe, created by the Big Bang. Each of the stones possesses unique capabilities that have been enhanced and altered by various alien civilizations for millennia.

Only beings of immense power can directly wield the Stones, such as Celestials, and the Mad Titan Thanos. Lesser beings would face dire consequences: Johann Schmidt was cursed to Vormir to guard the Soul Stone after touching an active Tesseract, Jane Foster became ill after being exposed to the Aether, Carina exploded when she touched the Power Stone; however, these effects can be reduced if a group is sharing the power among themselves. It is also possible to place an Infinity Stone (or multiple) inside a container to allow the user to wield the Stone's power without suffering the normal repercussions. Examples include the Space Stone inside the Tesseract, the Mind Stone inside the Scepter and later in Vision's forehead, the Power Stone inside the Orb and later the Cosmi-Rod, the Time Stone inside the Eye of Agamotto, the Reality Stone as the Aether, and all of the Infinity Stones housed in the Infinity Gauntlet.

When Thanos successfully collected all of them, he used their phenomenal powers to annihilate half of all living creatures in the universe. He later used the stones' power to reduce them down to atoms, as to prevent his work from being undone and to keep himself or anyone else from abusing their power.

Creation
Before the universe began, six singularities existed. The Big Bang then formed the six singularities into concentrated crystals, and sent the six stones hurtling throughout the universe. Each stone represented a different aspect of the universe (Space, Mind, Reality, Power, Time, and Soul). The first of the Infinity Stones to appear in the Universe was the Soul Gem, which was given to Adam Warlock by the High Evolutionary.

In the distant past, the Power Stone was used by the Celestials as a means of placing judgment upon worlds and their populaces, wiping out entire civilizations by touching its power on the planet's surface. However, the stone was just as dangerous to its handler as it was to the societies against which it was used, as its insufficiently powerful handlers were destroyed by its power.

World War II
During World War II, Johann Schmidt became fascinated by tales of ancient mythical powers and decided to locate the Tesseract to discover its true power. In 1942, Schmidt invaded Tønsberg and found the Tesseract in a box hidden behind a sculptured mural of Yggdrasil, the world tree. Schmidt took the Tesseract back to HYDRA Headquarters to be experimented on by Arnim Zola. Schmidt and Zola were able to harness the Tesseract's power to create and fuel their weapons of war.