Infinity Gem (Earth-616)

An Infinity Gem or Soul Gem is an object with universal power. In Earth-616, thr are only 6 known gms.

Using them together with the infinity Gaunlet, their power becomes nearly multiversal.

According to the most commonly accepted origin story the six gems are the residu of an all-powerful being who committed suicide out of loneliness.

Yellow gem (reality)
The Reality Gem allows its user to alter reality to what one wants or break the laws of reality and logic such as making 2 + 2 = 5, as well as the laws of physics. Minor uses allow one to resurrect the dead, distort reality around someone so it is incomprehensible, or other things that would normally be impossible. More powerful uses allow one to create any type of alternate reality one wishes. At its peak when backed by the other gems it allows one to alter reality on a universal scale.