In the beginning of time, when the universe was formed, six elemental crystals went to different parts of the universe.
Each stone represented a different part of creation and if combined, could have the power to do anything. All these stones were powerful and were sought after by evil and power-hungry beings who sought to use their power for their own purposes.
Five of the six stones were hidden in the known universe but the sixth, the soul stone, was hidden by the Fates. Using their knowledge, they chose one soul in existence who was worthy of carrying the soul stone as a part of them.
After hearing of the plan, people searched for millennia to find the one lucky person who had so much power at their fingertips, but the person was never found.
Eventually, certain planets and races forgot about the stones and the soul stone legend. They focused more on science then magic.
During this time, the Fates sent the stone to their chosen bearer. This soul was a human female, born on Earth, and was the only person strong enough to carry the stone.
The sorcerers of the planet, who had found and were guarding the Time Stone, read portents that let them know that the bearer was on their planet, but they could not locate her.
But still, on August 24, 1988 at 5 PM in New York, she was born.
The soul stone had arrived.