This is a big plot-point in the Dungeons and Dragons setting Dark Sun, where ancient magic battles had destroyed the planet, draining life-force from it and turning it into a gigantic dustbowl with a silt sea.
For every action, there is an equal and opposite reaction. Magic creates – but does it draw its power from anywhere? Do your wizards drain mana from the land, or does the very existence of supernatural energies warp the landscape?
In my world, magic has an effect on physical and mental health, which justifies IMO religious tenets promoting careful use of magic, or use of magic only at the gods’ direction. Even a shaman who carefully regulates their contact with spirits can end up going mad and ending their career in an asylum talking to thin air. Someone exploiting a talent which gives them useful divinatory information might suffer a sort of aphasia if it’s misused or taken for granted. (An in-universe saying is ‘if you exploit magic, magic exploits you’.) Physical magic such as telekinesis, teleportation/spirit-walking and transmutation has a physical pay-off in terms of fatigue or even coronary overload. So this topic also covers how magicians moderate and balance their use of power with concerns for their person, for other people, and for their environment.
Also, I had an idea, based on my own inability to draw out realistic street plans, as regards the old ‘if a tree falls in the forest…’ conundrum. If a city street is unobserved, does it shift slightly? Can a person get lost simply because the fey want them to be misdirected? Does magical energy in the world alter physical reality to the extent that things become uncertain? I know this sounds a bit like something out of Discworld, but I think with translating some folklore into fantasy fiction, it could be an interesting plot device.
So questions, as usual:
- Is magic environmentally unfriendly? What, if any, life-force does it take from the world, and if it does have an impact, what step do magic-users, druids, priests etc take to husband resources and pay the environment back for its sacrifices? Are there any anti-magic groups which protest the magical equivalent of fracking?
- Does magic have odd effects on a person’s body? Do people have different tolerances, strengths, or weaknesses? Are there any socially-imposed restrictions on its use? Are there magical doctors who know how to recognise the impact of too much magic use on a particular person?
- Can magic influence the natural or human-created environment? Are there mischievous – or even evil – sprites which confuse travellers by shifting roadways? Kind angels who will alter the flow of a river to prevent a disastrous flood destroying human crops? Are weather or even climate patterns altered by magical catastrophes? Does magic actually do this itself as a neutral or ‘super-natural’ force warping normal physics or physical realities?