DISCLAIMER: This is just the inkling of an idea for a world, don't expect much to be here yet.
A world where magic users exist, but are extremely rare. However, they are basically godlike. They lives alone with lands the size of entire nations, alongside actual nations. New magic users are only born every couple hundred years. Not quite sure yet why magic users are so isolated. Maybe because the use of magic has very chaotic/dangerous side effects, maybe because all (or at least almost all) magic users are so powerful they become fairly corrupt, so people just leave them alone for fear of getting killed/harmed/etc. Maybe because they aren't capable of effectively controlling their magic, so even unintentionally, they would end up killing pretty much anyone who goes near them. Would be interesting to play with different times in history, where eventually in later centuries, there are a lot of people who don't even believe that magic exists, because nobody ever sees it, they just get told not to go to a particular place. While in earlier centuries, maybe there is more interaction between magic users and others. Maybe magic was somehow corrupted as some point, leading for the need for magic users to remove themselves from the world, while before the corruption they did great things to help the world.