All magic in this world is tied to your ability to access Ziz's Magic.

Before the Time of Great Beasts, when the gods gave us the magical scripts, only Physical Magic existed.

Unknown comes in many forms. It can be borrowed from magical creatures or gods by Clerics, Paladins and Warlocks. It can be in your blood as with Draconic Blood Sorcerers. But it is most commonly very physical. A person might have been involved in a magical accident or perhaps an odd birth, resulting in one magical crystal per spell slot on their body. It glows with energy til they use it and reforms each night. Perhaps they have their magic tattooed to their body, or a bolt of lightning hit them as a child and a scar on their forehead grants them their powers.

This type of magic is often very physical in its creation, involving body movements to trigger the physical attachment you have to the source, or reaching for and operating religious regalia to call upon your gods.

Unknown was developed by the Gods in order to manipulate magic in this world that was unlike their others. Each element has a language, and each spell can be learnt from a number of different languages. For example "Cure Wounds" could be learnt from the Blood  Light, Fire or Water Script.

These scripts are carefully guarded, and while taught widely, only taught to specific people. A certain city might traditionally teach from the Air Script. Most people in the city will learn the basics, in case they ever need to fight the Great Beasts, but those that master it will be able to fly around the city's many levels, as when most citizens know featherfall, verticality issues become a thing of the past.