Based on the idle game http://www.lerpinglemur.com/arcanum/.

A standard-issue medieval fantasy world for the most part. It has local plane-shifting magic and an associated worldsheaf of pocket dimensions, hells, friendly afterlives, and the like.

The magic system runs on the capacity of its users, once they've memorized enough otherwise-meaningless symbols, to generate mana from thematic objects and locations (water mana from ponds, fire mana from fireplaces, spirit mana from dreamcatchers, and so forth - there's lots of ways to get any given thing but, roughly, bigger and more-thematic things get you more mana). Mana capacity scales with study time and proximity to favored objects - for example, someone who carries a torch with them everywhere might develop a higher fire mana capacity, but only if they already had one.

It is uncommon to even develop a rudimentary pure-mana sense, since wizards typically only take one apprentice at a time and it's almost impossible to figure it out by yourself, and much rarer to put in the time to build up elemental mana of more than one type. Most adepts pick a specialty and either take up dungeon-delving, join a traveling caravan, or settle down in a small town.