Magic in our universe is often referred to as the only consitently inconsisent force. Unlike gravity, for example, which follows the same rules when an apple falls from a tree as when an ogre falls from a cliff, magic conforms to the will of the caster… for the most part.
It can be woven into consumable items like potions, poisons, and scrolls. It’s often used by the Grey Nomads in their curses, and has even been found to influence diseases like lycanthropy and vampirism.
Stronger magic is used to supplement gear used by adventurers on their quests. And long lost magical processes are said to have produced artifacts of rare and sometimes inscrutible power.