In a nutshell, there are spirits in various towns or islands that emit unique magical frequencies, and mages are like radios, able to tune into those frequencies.
The game is set on an archipelago where each island has a genius loci (spirit of the place) that emits a magical frequency of a particular type (fire, water, birds, the dead, illusions, strength, etc.). Mages are attuned to the island spirit from where they were born. That spirit’s frequency is strong even when the mage travels far away from their birth island.
Usually, however, the closer a mage gets to an island spirit, the more easily they can tune in to its magical frequency. Island spirits each have a token: an item, substance or ritual that acts like an antenna for mages. Use the token and the mage can access the spirit’s signal even from afar.
This creates cool quest fodder for mages. Say a mage is born on a water-attuned island and then travels to the island of a fire spirit. All the local mages on that island have some sort of fire power and the animals and environment are even attuned to the local spirit. And in comes the water mage, able to strongly access water (though not as strongly as at home). She might be feared or hated or an object of fascination on the fire island.
Add to that the spirit quest: if water mage could be there seeking out the fire spirit’s token. Obviously that is a quest in itself. If they gain the token, then they gain fire power. Which could be useful in their travels. It could also let them make steam, by combining their powers.
You could even add to this the idea that spirits can commune with attuned mages. What if all the ice-attuned mages suddenly felt compelled to journey back to the frozen island to witness a great event that they don’t yet understand.
Islands in between other island have an overlap of powers too. So, maybe not every island has a powerful spirit, and a small island between the fire and water islands is ruled by a small steam spirit.
Finally, the technology of the setting: with the analogy of spirits and mages being like frequencies and radios, it makes sense that radios would exist in the setting itself. I imagine dirigibles in a Lady Blackbird sort of setting, tuning the ship’s radio into distress calls, weather forecasts, even spirit forecast with islands moving like planets: “Vulcanus is moving in toward the Elysian island. Beware of high fire danger in the surrounding areas”.
This is just an idea I came up with organically, but I think there’s potential here. Feel free to use the ideas and if you do, I’d love to hear about it.