The power of magic was the power of the world.
It was a power that existed everywhere in this world. Human used their soul to control the power, turning it into reality based on their own ideals. Based on theory, it was a technique that could create any possibility. This was the initial form of magic itself.
The casters from the beginning were known to be sages which were born with strong souls and high intelligence. They were able to identify things which regular folk were unaware of in their lives.
They believed that the 'Psion' world was a gift from heaven. Using their own talent, they gathered 'psions' and turned them into 'psionic power'. Using this power, they created clean water out of thin air and raised fires. All these abilities were used to benefit their tribes to live on through the ancient era.