Every magical ability has an effect on the world. This is a principle I’m working to follow as I rewrite Featherfolk. My main magic system consists of special powers granted by spirits. The availability and breadth of different powers alters the setting and plot, but that’s the way it should be.
The poster child for what I’m talking about is teleportation. If characters in a fantasy story can teleport magically from place to place, why would they rely on x for sending messages, and why didn’t they use teleportation when event y or z occurred? Why do social problems a, b, and c still exist? Even with limitations on when or where or which characters can teleport, it’s hard to catch all these and keep things consistent.
I tend to shy away from teleportation, because it gives me a headache to pin down all the effects such a power would have on economics, politics, warfare, etc, but I still have to be careful with the powers I grant my characters.
Have any of you had to re-work a magic system to match a setting or vice versa?