The Script

The Script of Aither is the very fabric of the world, more commonly known as the very rules by which the world works. It dictates that the sun rises in the east and sets in the east, for instance, and was made by Pateras, Primordial God of Creation. Despite having the power to complete remake the Script, both Afrid, the Goddess of Life and Avalore, the Goddess of Death, are bound not to do so, as any large scale changes could destabilise the very world, causing it to collapse in on itself.
To alter or change the Script in any meaningful way is beyond any being that is weaker than a Primordial in power, but lesser alterations can be done by the Lesser Gods, or mortals; however, their alterations are considered meaningless in the grand scale of the world. The manipulation of the Script, and bending the very rules of the world to create fire, or summon creatures from other planes of existence, is known as magic, and different schools of magic are derived from manipulating certain parts of the Script.
Differing Realms of Reality are noted for being proficient at using different kinds of magic, as certain parts of the Script are more prevalent to them. Some creatures exist as pure contradictions to the Script, such as the Eldritch Horrors, created as embodiment of Pateras' wrath when he left the world in pure rage. Anywhere they go, they bend the Script around them, similar to how Lesser Gods can, but do it in a way that is entirely uncontrolled.
Some mortals have realised that their bodies are simply incapable of manipulating the Script in the same ways as Gods, as they Cycle was put in place to prevent such an event form occurring, causing the death of a mortal should they push the boundaries too far. Even immortals are not immune to this; however, their much lighter connection to the Cycle means that they can manipulate the Script to a much greater degree, leading to the most powerful mortal beings in Aither being demi-gods, archfey or others that have been able to eternally cheat death.