u/ElectroNikkel

So, the magic system for Velthir is, in short, based on a field responsive to repeating patterns, usually neuronal patterns that convey an intention to perform a change in the world.

This system gets indented with repeated intentions, be it conscious or instinctual, and thus the first mages or magic users were the flora and fauna of Velthir, the main continent of the setting that were indentating this field with different "metaconstructs" (The indentations that perform the reality bending feat desired when tuned with) for their different wants and needs.

So, you have stuff like spell bugs that shock, explode, teleport, poison or confuse you when feeling threatened, to predators able to magically enhance themselves for better hunting.

Thing is, since the Veil (The field previously mentioned) doesn't store energy, all casters have to use the energy of their very metabolism to perform these spells, albeit more advanced ones can leverage the energy of their environment.

This also gives birth to souls, spirits and even gods, but that's making the explanation longer than it needs to be.