Thing that has been seriously bugging me lately: The average D&D setting (not the player characters, the setting itself) seems strangely lacking in the resources necessary to remain functional in the face of what casters can actually do. While 5e (my current edition) does include tricks like Detect Magic, Mordenkainen's Private Sanctum, Nondetection, Truesight, and Counterspell, many of these are of higher level or short duration, requiring a setting with an abundance of mid-level NPC casters constantly employed in the mundane tasks of making sure yet another baron isn't scryed, teleported to and dominated. Meanwhile, who's looking out for the merchant emporiums ripe for plundering by any two-bit shmendrik with a Charm Person spell and a little patience?

I do recall that over the course of D&D's history a large crop of spellcaster counter-measures have been devised and presented in various core and splat books. Can anyone recommend some particular tricks of this sort worth digging up and adapting to 5e?

In the meantime I'm trying to think up (unconsciously recall?) some tech of my own, and I wouldn't mind critique. Here's something I've felt a real need for:

MAGIC ALERT
1st-level abjuration (ritual)
Available to Ranger and Wizard
Casting Time: 1 minute
Range: 30 feet
Components: V, S, M (a tiny whistle and a braid of copper)
Duration: 8 hours
  You set an alarm against unwelcome spellcasting. Choose a door, a window, or an area within range that is no larger than a 20-foot cube. Until the spell ends, an alarm alerts you whenever a spell or any portion of a spell's effect is cast in or into the warded area. The alarm only responds to spells and spell effects, not creatures or objects that are simply magical by nature. When you cast the spell, you can designate schools of magic or particular spells that won't set off the alarm. You also choose whether the alarm is mental or audible.
  A mental alarm alerts you with a ping in your mind if you are within 1 mile of the warded area. This ping awakens you if you are sleeping.
  An audible alarm produces the sound of a whistle for 10 seconds within 60 feet.

The goal with this spell here is to offer a cheap way for mundane NPCs like merchants or goblin tunnel scum to know something is up without completely blocking the PC caster's fun. Thoughts?

I think you want a system other than D&D.  

I started a similar thread call "rational magic" or some such.

But in setting.   Swords that glow in the presence of magic or certain schools of it.  

Out of setting.  In Eddings fantasy all casters can sense magic being done, and Rifts has the sensitive, which I think does that.  Butcher's Dresden files have a few techniques which an non-magical educated person can use to protect them from magic.  Circles, salt, cold iron, running water.

I took spell breaker and the morganti (soul destroying) weapons from Vald Taltos and made souls eating spell eating swords.  

Or just not let any one play a full caster. But again, you're not playing d and d.

Best caster counter: Fighters.

Other best caster counter: Surviving to level up.

Other other caster counter: depends on edition.

Casters arent the be-all-end-all you think.

• Limited spells per day (eg, 1 spell only at first level).
• "Chance to know" rolls that mean you will not necessarily be able to learn any particular spell you want (say, highly unlikely to be higher than 65%)
• Limits to the total number of spells you can learn of each given level.
• Extremely low hit points.
• Any spells gained at level up are determined randomly or still require the chance to know roll to be made.
• Long memorisation times for high level spells (eg, 15 minutes per spell level per spell).
• Few or no easy ways to reliably secure a  location in hostile territory for the time required to memorise lots of spells.
• Powerful spells can have possible risks or drawbacks (eg, teleportation might involve the risk of teleporting somewhere inimical to life)
• In wider application, a requirement for extended and difficult apprenticeships from a very small number of wizards who are actually willing to pass on their knowledge.

These things limit both the number of magic users and their ability to do whatever the fuck they want without consequences.

If you want to introduce means and reduce the power of magic, it appears counterproductive to do it with even more magic. So make non-magic solutions, like:

Flight and levitation spells do not work over water. That's why there are moats around castles.

Scrying and communication spells can be prevented with a circle of salt.

Rubies suck up magic fire. A ruby worth x gp, will reduce a spells damage by f(x) and be consumed in the process. Against area spells, the effectiveness is halved. Other gems might work in similar manners.

And so on.

The best caster countermeasure is another caster.

Most lords will have a wizard at hand ("magist" as BECMI/RC called them) who might detect and counteract magical attacks from charm person to finger of death. Clerics can also provide equal or better protection.

That, or burning them at the stake while they're low level. Sure, the odd high-level Merlin will slip through, and possibly abandon a life of secrecy at a time he or she can pose an actual threat, but nothing an angry mob and/or a squad of fighting men can't handle.

It is also quite possible that, where magic is tolerated, wizards will police their own to some degree.

I really can't answer the D&D side, as I belief that caster primacy is baked into the system.  You can set up setting specific solutions, which I did far in the past, dealing with rarity of components, rarity of casters and the following difficulty to find new spells and the subsequent rarity of magical items  (seriously.  potions were hoarded.  One caster finally found a book with a Fireball spell when he was 7th level, and it was like he had conquered the world).  

In my own game, magic is much more common, but spell ability reclamation and spell success are separate skills, so the magic using folk really need to work on many more areas to get really good at what they do.  When spells don't always succeed and reclamation is variable and needs to be leveled up as a skill in itself, casters aren't so likely to rely on/waste their spells.  Which makes them less powerful.

I think the one thing that I did that seriously nerfed magician power was ...

they get one spell for free when they level up. All other spells have to be researched (major money sink) or "acquired" (risky). I was absolutely amazed how getting only one spell, not two, created hard choices. There were some other changes I made, but that gave me more results than any other thing.

The other major change was to teleport. The magician casts it fast or slow. Fast, and there is about a 20% chance you merge with a wall if it's not LOS or "well known". LOS is unaided, and "well known" means you've lived there for a week. Slow, and there is a 1% chance you merge with a wall, but it takes about 10 minutes and there is a glowing anchor point at your destination. It's more of a long distance dimension door.

This allowed the players to teleport inside the gate or onto the roof, but not have a strike team appear right next to the assassination target. Then, you have a much more exciting black op job. If you want the scry-and-fry, then you have to go with summoned entities. And, they're a whole different kettle of slaad.

Edit: Oh, one other thing about teleport. If you do end up chewing plaster, it doesn't kill you. You take 9d6 damage no save. Not so bad, you say? Fine, but what happens is that the magician gets seriously mangled, the screams of pain and thunderclap from displaced air and material raises the alarm, and the upshot is the risk of capture goes up significantly. As we all know, capture is far, far worse than death to a PC.

QuoteThoughts?

My general opinion is that coming at someone in a crowded market or busy shop, waggling your hands and chanting ominously, maybe theres a puff of smoke or swirling lights, and then the person thinks you're their best friend ever, is a great way to get burned at the stake.

Quotescryed, teleported to and dominated.

This can be an issue. I tend to favor the idea that there's a lot of mistrust in the wizarding community over spell knowledge. Some people in the thread have already pointed this out with roll to know spell and all that jazz.

If a wizard is powerful enough to magically see miles away, teleport to that location, and then mind control someone, they've entered a realm of power where other wizards and demons and agents of light would probably be more concern than some baron in a keep.

Or just modify or take those spells out. Depends on the edition, of course.

Here are a number of mundane counters you can use to disrupt magic-users:

Darkness
Magic-users need to be able to read their magical texts and see their targets to cast spells. Denying mages their sight thus denies them their ability to cast spells. Something as simple as dark environments may be sufficient to counter low-level non-elfin mages.
Remember well that some mages can see in the dark, but also that darkness is not the only way to impair vision. You may use bright, flashing lights to blind or dazzle magic-users, or you may block their vision with dust, sand, or smoke. Dungeon Masters may consider equipping their kobolds with eggshell grenades filled with dust for hurling at a wizard's eyes.

Water
Water is a cheap and versatile tool for countering magic-users.
Water can put out magical fires, making it a hard counter for pyromantic mages. Water can also put out mundane fires from candles or torches, thus denying low-level mages light to see by.
Water makes perilous the use of lightning bolts. Mages must think twice before using electrically based spells while standing in water.
Water, especially falling water, can reveal the position of invisible mages.

The best thing about water though is its ability to exploit the mage's dependence on spellbooks and scrolls. Paper gets damp, ink runs, and spells are lost when a wizard's tome gets soaked.

Dust
Dust is potent defense in dry environments.
Dust can block vision, thus denying magic-users their ability to read and assign targets.
Certain kinds of dust, such as sawdust or flour, may be flammable. Mages should think again before hurling fireballs in such an environment.
Flour is a classic counter against invisible enemies. Throw packets of flour at any space where you suspect an invisible creature is standing to reveal their position.

Most importantly, dust could potentially be used to block teleportation. The rules make it clear that bad things happen when magic-users teleport into solid objects. What the rules do not make clear is how large an object has to be to considered a solid object. Dense particulates and debris in the air may be sufficiently hazardous to dimension-hopping mages.

Lead
Lead is known to block X-ray vision and the Scry spell. Lead may be able to block divination and magical sight in general. Dungeon walls should be plated with lead, or at the very least coated with lead-based paint, to block out prying eyes.

White Noise
It is well known that spells with verbal components can be disrupted with magical Silence. However, there are also mundane engineering solutions that can nullify sound in order to counter verbal spells with nonmagical silence.
We are brought again to the use of water in dungeon environments. Flowing water in certain acoustical environments could produce enough white noise to nullify sound.

Entanglement
It is common knowledge that certain spells have somatic components, meaning that they require precise and unimpeded hand gestures in order to function. Denying mages the use of their hands can deny them the use of their somatic spells. Manacles are sufficient for mages that have already been apprehended, but the trick is in actually apprehending them. To this end, one may domesticate giant spiders for their sticky webs. Alternatively, one may train kobolds to hurl pots of glue.

New Item: Kobold Anti-Magical Grenade
This item consists of an eggshell packed with dehydrated glue dust with flammable ingredients, lead filings, capsaicin powder, and the bare minimum of alchemical reagent required to radiate a the faintest of magical auras.
The item is meant to be loaded in slings and hurled by kobold minions.
The eggshell cracks on impact, coating all targets within a 20x20' area with dust.
The dust clings to invisible creatures, revealing their location.
The dust is an eye irritant, and can temporarily blind targets.
The dust explodes when exposed to open flame.
The dust bonds into a sticky glue when exposed to moisture.
The lead filings can make an area temporarily Scry-proof.
The alchemical reagent has no effect except to make the item radiate a faint magical aura. The magical aura prevents wizards from catching or grabbing onto the item with the Mage Hand spell. The magical aura can also distract and confuse mages with an active Detect Magic spell by making it seem as though all the kobolds are carrying magic items. The shear number of false positives may cause the mage to overlook items of true magical importance.

There's already a lot of good ideas here, but I like to go with the following set up for a setting:

1. Wizards are RARE. Like super heroes. There simply isn't one in every town, village or hamlet. Finding one to work for you, let alone convincing them, is a challenge.

2. Wizards only have the spells that have been given to them by another wizard or that they've found in existing spellbooks. No wizard "builds" (i.e.: no picking an elaborate combination of powers). If you realllllly want that scrying spell, you've gotta do research and either find someone who can teach it to you or maybe summon a demon and make a pact in exchange for the spell.

Those two things, I think, would help. Unless you really really want a high-magic setting, in which case other Wizards are what are needed as a counter.

You're making assumptions about D&D settings that aren't necessarily true (and certainly don't have to be true in your own setting). You're assuming:

* Spellcasters are common
* Spellcasters take an active interest in the mundane goings-on of men.
* Many spellcasters reach high level.

As I posted in the other thread, it's entirely consistent with D&D to posit a setting where:

* Only 1 in 10,000 people are arcane spellcasters.
* Most of those are level 1 because very few mages every go adventuring or do stuff to gain XP.
* Most are eccentric scholars obsessed with arcane matters and rarely leave their libraries or laboratories. They're are more interested in fascinating matters like the true nature of alchemy, or the origin of pixies, than in the mundane affairs of men.
* Those who are ambitious to learn more spells must adventure in perilous ruins to find them, and thus suffer a very high attrition rate.
* Those few who do take an active role in society tend to be tremendously jealous of rivals, and thwart one another at every opportunity.

Gods, there's too many to count. I only have time for just a few for now.

As already mentioned, the way older editions make casters search for spells or spend lots on research restricts caster power. It also offers an explanation of why M-Us go on adventures. AD&D 1e gives casters one new spell per level after level 1, but OD&D doesn't even mention this, so you could be harsh and interpret that as no automatic spell acquisition, or allow one random spell, or one spell of a higher level that is related to spells the caster already knows. It helps, also, if you assume M-Us are rare, and mid- to high-level M-Us rarer still, rather than making them common professionals available in any town or city. Make finding a 5th-level M-U in any given city into a crapshoot. Make finding 9th level M-Us an adventure.

Scrying and teleport aren't as foolproof as a lot of people imagine, at least in the editions I'm familiar with. The only guaranteed way to see into an area you've never been to is Wizard Eye, which has a limited range. Clairvoyance also has a limited range, and can be stopped by a thin layer of lead. Is the typical D&D setting up to the task of inventing lead paint? You decide. Crystal balls are blocked by lead, as well, plus they are unreliable when used over a great distance or when the target of scrying is not well-known. The chances aren't specified in OD&D. In AD&D, the "great distance" restriction is dropped (except for scrying another plane,) but it does break down familiarity with the target into several categories, with low chances to scry someone you've never met unless you have one of their possessions.

This matters because Teleport has a high risk of death if you've never been to the target location, and scrying only counts as "seen from a distance". The chances of death are much higher in OD&D than AD&D 1e. I suspect later editions softened the restrictions even more. Note also that since this death is caused by teleporting into an object, any mundane measure that increases the chance of materializing inside something else will be an effective teleport deterrent. So, rotating rooms powered by waterwheels actually make sense! And if any amount of solid matter carries a risk, perhaps a lot of dust or other particles in the air creates a problem as well.

Since in Manual of the Planes gorgon's blood and the blood of other creatures with petrifying gazes is said to block scrying or entry from the ethereal/astral plane, perhaps it affects teleportation as well. Dimension Door is explicitly mentioned as using the Astral Plane for teleportation, and it's my personal explanation for the more powerful Teleport spell as well.

Oh, and it should go without saying, but any spell added in a later edition that only exists to eliminate a restriction on a lower-level version of the spell should just be expunged. I'm thinking here of Teleport Without Error. Why is it without error?  We know why errors exist for the lower-level Teleport spell, but why does the error go away for this higher-level spell? What does it do to make that error go away? Seems like just a load of BS. Kill it.

I really like magic rules that favor components and ritual, require that spells/grimoires be found and deciphered (lots of them are trapped/cursed), and carry risks that spells results can vary and might blow up in your face.
Also, I prefer settings where magic users are feared and perhaps hated... so being seen casting spells can have repercussions.

Also also, there's nothing saying you have to allow EVERY spell in the rulebook. Some might just be rumored to exist.

I'm saying that as a Player and a GM.

Losing a spell when struck by casting changes things a lot. As does sheer low survivability while trying to "adventure." So does 1 free spell per level, find the rest. And so too does percent chance to learn a spell. And obviously spell casting amount limits, be it slots or spell points or whatever.

Those 5 are the big ones in my experience. Built in randomization risk of strong magic also helped, like TSR's Teleport, or unknown spell durations.

(edit: e.g. I'd limit 5e total cantrips to INT attribute value (not mod) per long rest, if I were to reintroduce spell casting amount limits.)