D&D 5E Limiting use of cantrips - what are the consequences?

[crashtestdummy]

Because with unlimited casting you never need to pick a lock, or beat down a door, or cook a meal, or struggle to cool down the overheating room because you can make ice, or you poison the rats infesting your house or you use shocking grasp to invent lightbulbs, you don't need torches because you literally just continually cast fire bolt.

But that's not taking into account that casters only have a limited number of cantrips. They can't cast any cantrip any number of times. They can only cast a selected subset of cantrips any number of times. And, of course, it's the cantrip you don't have that would be most useful in any given situation (like the last session I played where having Friends would have been really useful, but it's not on the list of cantrips my character knows).

 

[Unwise]

Just a sidenote to the OPs original objective about making magic rare but meaningful. In my experience, making something rare in and of itself makes it more powerful.
A few cases in point:
- Infantry do not allow for fireballs, so group up a lot tighter in battlefield formations.
- Nobody has any way of detecting you when you are invisible.
- Castles have no teleport protection, you can zip in and out as much as you like.
- Nobody has a way to stop you scrying on them.
- Enemy strongholds have nothing to stop you passing through their walls.
- Illusions are near unheard of, people will believe whatever they see. If you pretend to be somebody, they will have a very hard time explaining what really happened later.
- You can get away with murder, as nobody can track your spell signiture, speak with the dead, scrye on you or understand how you could possibly have got through a locked door unseen etc.
- Nobody bothers to lock the top of their towers, how could anybody get up there?
- Prisons make no allowance for mages, a mage of theif/mage will get out in under a minute.
- You can intimidate people very easily if you use any arcane power.
- If you can prove you can do it, imagine what people would pay for Sending or Divination spells?
- Being able to heal anybody with magic makes you into a walking saint, an object of devotion.

The simple context of a lower magic world makes magic more powerful, vastly so in some cases. Beware of also increasing its power mechanically.

 

[Merchant of Shadows]

With unlimited melee attacks why do you need to pick a lock or beat down a door? With firebolt you don't cook meals, you destrow them. Ray of frost rearanges the ambient temperature to achieve its effect so is no more usefull in cooling down an overheating room than opening the door of the fridge instead of getting an air conditioner. If you are wizard who is killing trolls and have problem dealing with rats - this is retarded. You don't need torches or inventing the lightbulbs, because even limited casting of the light cantrip is enough.
If you don't need mages and wan't magical effects to be rare just ask your players not to play a magic class using class. Having the magic to turn a man into stone, but lacking the magic to kill a rat is simply stupid.
If you want to avoid reckless use of magic - simply implement a mechanic similar to the wild mage surges for all castings and inform your players in advance about it.

 

[Gadget]

Because with unlimited casting you never need to pick a lock, or beat down a door, or cook a meal, or struggle to cool down the overheating room because you can make ice, or you poison the rats infesting your house or you use shocking grasp to invent lightbulbs, you don't need torches because you literally just continually cast fire bolt.

I'm not sure which cantrip allows you to get around 'picking a lock', unless you just mean to pew, pew the door down, which does take time and causes a certain amount of damage and noise, not to mention can cause a fire, etc. I'm also not sure what cantrip can 'cook a meal'; flavor one, yes, but not cook one. As for cooling down an overheating room, there may be one in the Elemental player's supplement, but Ray of Frost (if that is the cantrip you're thinking of) does not 'create ice' but merely a blue-white ray that does cold damage to a 'creature' in range. It would be perfectly valid to rule that it does nothing to non creature objects it hits. As for shocking grasp and lightbulbs, that is a shockingly convoluted use of the cantrip, especially when one can use the light cantrip to better effect. But the light cantrip does make your point (along with dancing lights). Continually casting fire bolt also seems like a poor substitute for the aforementioned cantrips, not to mention causing potentially unintended side affects like collateral damage and starting fires. I would also think the limited range and area of poison spray might make getting rid of rats a bit trickier than it seems, as the little buggers don't often present themselves in the open, but point taken.

 

[The Human Target]

Because with unlimited casting you never need to pick a lock, or beat down a door, or cook a meal, or struggle to cool down the overheating room because you can make ice, or you poison the rats infesting your house or you use shocking grasp to invent lightbulbs, you don't need torches because you literally just continually cast fire bolt.

None of those things are true.

 

[Sunseeker]

Eventually, they'll go back to 3E-and-prior-style of hitting things with a stick.

 

[Wuzzard]

I think the OP is confusing a game rule, with how the game world might work. There is no direct correlation. The player rules are not a simulation of the game physics. You cannot infer the rest of existence from the PHB. Having a cantrip be unlimited does not necessarily mean that a caster can continually cast it, once every six seconds, forever. Maybe it does; that's for the DM (and players) to decide. What it does mean is that you are free to dispense with the minutia of tracking usages of cantrips. You've got enough of them for the foreseeable game day, however long that may be.

 

[bedir than]

None of those things are true.

let's work with a simple one.

What in the rules prevents a PC with unlimited cantrips from casting Fire Bolt as a light source?

 

[crashtestdummy]

let's work with a simple one.

What in the rules prevents a PC with unlimited cantrips from casting Fire Bolt as a light source?

The fact that the cantrip doesn't state it provides illumination?

I suppose you could use it as strobe effect, with one flash every six seconds, but I pity all the characters acting on a different initiative to the caster because they'll still be in the dark when it comes to their turn...

 

[bedir than]

The fact that the cantrip doesn't state it provides illumination?

I suppose you could use it as strobe effect, with one flash every six seconds, but I pity all the characters acting on a different initiative to the caster because they'll still be in the dark when it comes to their turn...

if tracers can provide illumination how would a magical bolt of fire do less?