I saw something like this asked on the GW2 Reddit ages ago and it has stuck in my mind since. There are a lot of things you can imagine to make fantasy a more tangible reality but for some reason, combining the idea of scent and magic really paints a picture for me.
Here are a few of mine;
Embalming fluid, rotting wood, worn leather
Steel, gasoline, grease
Pine, sweat, camp fire
Witchery [YWY] | Maguuma | Diamond Legend