Aether Formulas.
The secret language of the universe that allow cultivators to bend the rules of reality as they see fit by manipulating the fundamental energy that composes it, aka, aether.
But how does a cultivator tap into the power of these fabled formulas and begin making reality their plaything?
By carving the formulas into their souls of course.
Literally.
All mortals, hell, all souls are capable of tapping into the aether and manipulate parts of it in minute to negligible amounts.
Think of the soul as an unrefined ingot of copper and aether as electricity, one could technically use the ingot to store and conduct electricity, but it won't be very good at it.