What Magic Would Be Most Realistically Most Impactful?

[Kaodi]

As someone who has been spending a minimal amount of time outside many days trying to cut down a WHOLE BUNCH of weeds and saplings and sweating like the fat pig I am I was wondering about what in-game abilities and adaptations would be wildly popular and powerful and impactful (outside of healing magic). Being able to work outside comfortably in the heat or cold is a low level effect in D&D/Pathfinder (Endure Elements) but would be a massive quality of life improvement. And if it was not one that could be achieved with magic, there are a lot of different kinds of people who could possibly command a premium as seasonal workers due to fire or cold resistance, or as industrial workers due to acid or electricity resistance.

Another way to look at it is how in the world of Avatar lightning bending is an incredibly rare skill but a century later it widely used for industrial purposes. A lot of magic could have practical uses that does not really get explored much in game because most people are not here to play Magindustrial Revolution & Clockwork Dragons.

 

[Umbran]

There is an element that we'd need to address in discussing this, that most RPGs do very poorly: demographics.

How many wizards/druids/clerics/users of any particular power are there in the world? That puts a bound on how impactful a power is on a broad scale of a society.

 

[Blue]

Okay, when talking about hiring for acid or electrical resistance (a great idea!) it would seem that you are positing a world where the magic is acknowledged and present in enough quantity to make that reasonable.

I'd go for something like Zone of Truth or other magics of that ilk. Again, with the acceptance and potentially commonality, I think it would revolutionize human's justice systems and politics.

Low level divination would I think would be eagerly sought after. Even Augury's Weal or Woe would be useful from Project Managers through CEOs, all levels of military, and Heads of State.

Plant Growth. A single 8-hour casting enriches all plants in a 1 mile diameter for a year, yielding twice the food. Think about that in a lot of countries, especially ones where distribution is hard. But really, you mentioned healing - with all of the healing, cure disease, regeneration, and raise dead we might reduce early death that having more food in the same area is needed.

Smaller things - Locate Creature to help in rescue efforts. Geas for short term legal repercussions. Illusions for storytelling, entertainment and advertising.

Just about any spell that people have complained "breaks the economy".

I'm leaving out planar travel spells, don't know how you envision them in the real world.

 

[GMMichael]

Lightning-magic spawned an entire D&D setting: Eberron.

I'm not a big fan of races that have inherent magic abilities/resistances, exactly because of their consequences on macro-economies - like demand in the workforce. Except I usually think of it in the more medieval or bronze-age way: slave labor. Elves don't sleep? That's around-the-clock work!

So, despite your premise being such a slippery slope, I'm going with mind-control/mind-reading as the most "impactful" magic. Because it doesn't really matter how impactful your magic is, as long as you can make people believe in it.

What if you knew a spell that would make you enjoy weeding?

 

[Dannyalcatraz]

Adding to the good contributions above:

1) Continual Light/Flame: light without the need for fire. This reduces serious hazards from open/uncontrolled flames on land, in mines, at sea, etc., from nighttime crime, getting lost or predation in the wilds.

2) any magic that can result in perpetual motion “free energy” type effects. That includes automatons, undead, and almost any magic that can produce long/permanent access to elemental planes or energy- everflowing water for mills, eternal flames for heat & steam, unceasing wind power. Even access to elemental earth could provide cheap building material or ammunition for war engines.

3) any magic producing long-term access to other planes of any kind can be invaluable in waste disposal, leading to reducing disease vectors.

4) any magic that can replace or rein in the scope of someone’s job, especially if the job involves skill. Mending, for instance, reduces the need for a lot of “bulk” skilled labor.

 

[Aldarc]

Healing. How many village midwives will likely have the Stabilize cantrip? Birthrates go up. Childbirth-related deaths go down.

Outside of healing magic? Nature magic that can boost the agricultural output and food supply.

Think about how the proliferation of relatively lower-level magic will contribute to socio-economic impact of a culture. (Also think about who can afford what.) What would access to guilds providing Continual Light spells do for a town or city?

Blasting spells will also change how people fight in mass combat. Smaller, mobile formations that decrease the threat that a spell like Fireball would achieve. Or maybe even line formations that spread troops thin to prevent fireball. Troops protecting their magical artillery units. And troop formations designed to neutralize magical artillery.

Overall, never underestimate the "little things" about magic that have a much bigger impact than what spells like Wish can achieve. This is the lesson enshrined in Eberron.

 

[Dannyalcatraz]

Almost any combat magic you can point at and magical creatures- domesticable, trainable or negotiated as allies- moves the way war is prosecuted away from pre-gunpowder offensive & defensive tactics to something more akin to the 20th century forward. That includes defensive combat engineering shifting from open-topped castles to bunkers, trenches, and a general lack of old-style battlements. Given the number of tunnelers and magical earth movers, any kind of earthworks are going to be more at risk, and possibly abandoned as a tactic in most situations.

 

[Doug McCrae]

Another other important question is: are the rules complete? Does magic exist in the game world that isn't covered in the game rules because it has no relevance to the assumed activities of the PCs?

 

[Doug McCrae]

Plant Growth is the most impactful spell in 5e D&D.

EDIT: At least in the core rules. The cantrip Mold Earth from Xanathar's Guide to Everything beats it.

 

[Umbran]

That includes defensive combat engineering shifting from open-topped castles to bunkers, trenches, and a general lack of old-style battlements. Given the number of tunnelers and magical earth movers, any kind of earthworks are going to be more at risk, and possibly abandoned as a tactic in most situations.

But.. bunkers and trenches are earthworks.