Containing a Mage with Little or No Magic

[Kadzar]

In the course of fantasy law enforcement, mages would present a particular problem, what with their spells and such being pretty nasty tricks they always have available to try to escape from or harm their captors. So what is a state or other organization supposed to do?

Well, I may have one possible solution. Assuming this spell sorter (http://donjon.bin.sh/5e/spells/) isn't some way in error, there are apparently no spells that have neither somatic nor verbal or both. So if you have a mage both bound and gagged, they won't be able to do anything (unless they're a Sorcerer with Subtle Spell, but I'm not sure anything short of the Imprisonment spell or some sort of permanent antimagic field will stop them).

However, there is the tricky issue, for long-term confinement, that you probably don't want them dying of starvation. Assuming your world doesn't have feeding tubes or the like, it seems magic will be needed here. This may be one of the few times where the Silence spell being castable as a ritual actually has a use. You can now feed your prisoner without fear, though remember that you have to put the gag back in before the spell runs out.

Alternatively, if you don't want to have to bring a caster in every time you feed your prisoner, Mordenkainen's Private Sanctum can be made permanent, and has the ability to prevent teleportation into or out of it's barrier, among other effects. Though that still doesn't stop certain spells like Vicious Mockery or Immolation, but they and many spells like them require you to see your target, so they could be stopped with a blindfold. Spells this won't work for include several purely defensive buffs, Darkness (though this requires a material component, and doesn't do much), Destructive Wave (damaging, but 5th level spell only available to Paladins, Tempest Clerics, and Bards through Magical Secret, of course. Might be kept in check by requirement to strike the ground.), Dissonant Whispers (damaging and only 1st level, but requires the target to hear them, so could be blocked by earmuffs), Glibness (dangerous, dangerous lies), Sword Burst (damaging, but you could maybe feed them with a 10-foot pole, Warding Wind (not really dangerous, but, like Darkness, annoying for anyone who gets near them), Whirlwind (damaging, but requires material component), and Wish (but if you're imprisoning someone someone who can cast Wish, you probably don't want to be taking any chances). And while creatures can't teleport in or out of the sanctum, technically it seems like they could teleport somewhere inside, and I think that that might let them get out of their bonds.

You could maybe also use Hallow (to get permanent silence or anti-teleportation), but the Charisma save makes it not so great.

Does anyone have any other ideas on this subject?

[JellyPooga]

So what is a state or other organization supposed to do?

1) Ban the teaching of magic.
2) Burn all texts and histories that bear mention of magical practices.
4) Make utilising magic in any form a capital offence.
5) Outlaw the mention of any folklore, tale or song that contains magic.
6) Hunt down the bloodlines of all those that have used magic or had contact with magical, supernatural or extra-planar beings.
7) Crush your enemies, see them driven before you and hear the lamentation of their women.
8) Rule with an iron fist. Skull decor optional.
9) Be eventually defeated/overthrown by your choice of a) a rebellion, b) a party of adventurers or c) your own over-inflated sense of self worth.

[Naanomi]

If you need to keep them humanely, poison that mutes or paralyses, complex manacles and mechanical gags?

If you don't need to be nice, removing fingers and tongues?

[ClintACK]

Interesting.

In past editions, there was a simple answer. Beat the wizard unconscious, then stabilize him. He's now lost all his memorized spells. Deprive him of his spell book, and he's basically a well-educated peasant.

I wonder if you could make a Wizard fill all his Spells Known with innocuous things (like Comprehend Languages) as a condition of letting them go from Hannibal Lecter treatment to Gen Pop.

[Belac93]

A silence spell and rigid gloves. Or, just cut off their tongue. A very low amount of spells have only somatic components, and most of those are illusion spells.

[TheManicMonocle]

For part of the time you could put the wizard in an extended magical sleep

[Spore]

Well, OP is not only speaking about Wizards. I think he means all arcane casters. If you don't want to get all Inquisition on them and mutilate them, I'd suggest you hire or train your own arcanists. Our setting is technologically advanced and so uses armwrists to document all magical activities of registered mage. Not being registered is illegal.

But I have also toyed with the thought of an Eldritch Knight similar to a Warden (from Warcraft) as a PC. He would have been a magically talented martial fighter. As the characters have levels, he would guard levels of rogue casters who he certainly be able tocontain in combat with 2-3 of his comrades (usually a knowledge Cleric and an Abjuration Wizard). Having the majority of casters to be low level eases the stuff up a bit.
The inquisition might have a 9th level cleric and a bit of ressources. Just hallow the crap out of prison cells. Just bar extradimensional travel everywhere and prepare a few silence cells for especially wild specimen (remember, people tend to go mad in complete silence). Cast Geas on renitent casters: "You wil comply with all our wishes, be it of the guard or the inquisition."

Casters are high security material so each offender has to be treated individually. But yeah, if you have a dangerous necromancer (or worse, a lich) you are better of cutting out his tongue and chopping off his hands. That was the problem with our campaign's BBEG. If he were killed, he were to just reform on place in 1d6 rounds (he carried a magical pocket watch) and killing him without the watch would have made his ally high priestess just cast true ressurrection. So the inquisition just chained him to the wall in an permanent antimagic field. He eventually escaped due to his importance for the villains' plans but I figure this was a large scale attack on the prison fortress.

Uh, you have to mutilate or kill them. Low level casters can probably be easily restrained with manacles and a gag. You have to feed them manually. Anyhow, there is no way you can keep any high level D&D 5 character in a prison for long if they dont want to. A barbarian eventually breaks prison door, any sizeable stick counts as a club. A warlock could use their invisible familiar or a summoned weapon. Wizards and Sorcerer are just the easiest to be held down by cutting off their magic and the hardest to catch if they have their magic. Holding a wizard is binary. Either you constrain his magic or he flees.

[SharkForce]

you don't lock up a powerful spellcaster long-term. you either kill them, if you think they're not likely to ever play nice, or you release them and extract something in exchange.

in the short term, keeping them in a dark area (many spells require LOS) accessible only by tunnels (don't let them know the path of said tunnels when you're bringing them in), potentially with multiple locked or barred doors, with the spellcaster spending most of their time bound and gagged, will generally hold any spellcaster you can plausibly hold.

unless of course you actually live in the tippyverse. but that defeats the point of the question of how to accomplish the goal with little or no magic.

(though actually, as a technicality wearing armour that you aren't proficient in prevents all spellcasting, even for spells with no somatic component... YMMV)

[TheManicMonocle]

Another thing, idk if you've read the wheel of time series but in it there's a special tea that, if you trick a caster into drinking it, it disables their magic for one hour, then you just gotta force them to drink it after that

[N810]

Anti-magic collar made of a rare naturally occurring material.

[lunaticfringe]

Wire jaws shut. Enjoy the Soup!
Repeatedly break fingers/hands until Somatic finger wiggling is always painful.
Demiplane Prisons like the Shadow Zone or Prison 42

Edit: Prisons/Jail is for the Penitent/Remorseful Manslaughterers & Negligent, every one else just gets the Axe.

[Joe the Rat]

I introduced an herb that disables spellcasting for 24 hours when prepared as an extremely strong tea (as in "smells like eucalyptus explosion the next room over" strong). It can also be used as a poison, but it is most effective ingested.

I can't think of any Somatic-only spells, certainly none that are offensive. A muting or stuttering poison combined with a lack of spell foci should keep you covered.

Making a caster wear chain mittens or plate mail gauntlets should prevent somatic casting while allowing them to feed themselves, provided they aren't heavy armor proficient. If that's too cheesy, make them wear ring mail. That's not a huge expense for disabling casters. This works best if Verbal only spells are rare, or not known to the caster. And they aren't heavy armor proficient (which is a fair assumption regarding casters, but makes for a fun surprise for your escape plans).

[CursedRhubarb]

Almost complete sensory deprivation is about the only way. They'd need to be gagged, blindfolded, deafened, and their hands bound.

A nasty side effect of complete or near complete sensory deprivation tends to be madness though. Ever seen the videos of people in a lightless room that has zero echo? Alone in the dark and the only sound is your own voice (altered due to the lack of echo) and the sounds your body makes. You eventually can hear your heartbeat and the sound of your blood moving along with all your digestive sounds.

People tend to want out of those rooms very quickly.

[Mith]

Rough Idea:

Homebrew a herb that knocks out a caster guaranteed, and if they fail a Con save, they lose their highest spell level spell memorized. Multiple doses raise the DC of the Con check, and the number of spell slots lost. There is a percent chance on complications on a failed save due to toxicity. An antidote can reduce the percent chance, but not nullify it. Once Spell slots are lost, a lower potency brew interferes with Cantrips.

So you can conceivably shut down a caster, while taking some risks with killing them.

[CaptainSarathai]

Is cold-iron not still a thing? That's what we've always used, both myself as a DM, and when playing with other groups; bound, gagged, and chained in cold iron.

Failing that, if you wanted to keep someone from casting, I would go full medieval on them. Iron masks and similar devices have been found, which have a metal protrusion into the mouth; it wedges the mouth slightly open, but forces the tongue down, and with the chin keeping you from opening, and the plates keeping you from biting, you're unable to form words. You can still be fed, though, if given soup/liquids.
For the hands, use metal gloves with individual fingers. They cannot move the hands at all. These are shackled into the wrists or (for barbaric effect) affixed with a spike through the palm and locked on the outside.

I played a witch-hunter character once, I have plenty more ideas where that came from ;)

[Breaklance]

Always been a fan of series (books/tv shows) that have ways of taking away special abilities.

I'd just maguffin an item for it into my own world. Manacles of the Magi - two brackets that when have no apparent lock and magically weld shut when placed. The left one prevents somatic component and the right verbal component on the wearer. Can be broken with a special hammer and chisel, or excessive force, or a very successful dispel.

The wearer would be hard pressed to get themselves out of them without breaking their hands or otherwise would need help to do so

[Corsair14]

If its law enforcement for a major entity, simply have a high level wizard cast a sort of permanence spell on Silence on the cell for wizards and keep the prisoners hands chained or use the simple expedient of removing the fingers

[Kadzar]

Keep in mind that this thread isn't about if it's a good idea to keep a mage locked up, only if it's possible.

I will admit I only really took spells into account in the OP, not class features (mostly since I was mostly only thinking of using this against NPCs), and I didn't factor in spells that are usable outside of being cast, like Find Familiar.

As for class features, at least in the PHB, the only things that seem like problems are: Trickery Cleric, which has a Channel Divinity that apparently doesn't require a holy symbol; Druid's Wildshape, which I don't see any way to counter; Eldritch Knights can summon their weapons, though I'm not sure it will do them any good if they're properly bound; Level 20 Devotion and Vengeance Paladins can be a real problem once a day; as I mentioned before, Subtle Spell Sorcerer's sully your schemes; Chainlocks have nasty pets, and Bladelocks have the same problem as Eldritch Knights, but you can't sunder their weapons; Conjurer's could probably make something contraband, and Transmuters could weaken their bonds unless you make them out of something they can't effect. This is all assuming you keep the prisoner bound, blindfolded, and gagged until feeding, when they are silenced.

[DragonSorcererX]

...Sorcerer with Subtle Spell...

Yes! S*ck my Metamagic Mundane Plebs!

[VoltaicVitriol]

back in second addition, there were to look. I recommend taking out an old copy of Volo's Guide to All Things Magical ( and boy did elminster have some Choice words to say about that title) and reading through it. Most of it is setting fluff. There are some card game rules, but they are mixed in with verbose descriptions.


For instance, he lists a number of materials known to be able to block teleportation effects. Certain types of Stone from the underdark being the top of the list, but any mortar or grout with a certain percentage of Gorgon blood mixed in can have the same affect. Certain rare types of wood negate knock spells. Thinking logistically this means that there is an entire hidden Market for exotic materials that could be the foundation of many quests. both for legitimate law enforcement purposes and for less noble organizations seeking to protect themselves.

[Sigreid]

In the real world I would restrict the use of their hands and keep snake root in their food. Snake root disables vocal chords (it's also known as the mother in law plant). There could easily be a similar plant in any fantasy world known to herbalists and poisoners.

Beyond that, only a few spells would serve to get you out of an oubliette.

[RickAllison]

A key thing to remember is that this falls apart at higher levels. Contingency+Freedom of Movement ensures those manacles, oubliettes, and such don't help . Poisons are unreliable because resistance isn't hard to come by.

[Sigreid]

A key thing to remember is that this falls apart at higher levels. Contingency+Freedom of Movement ensures those manacles, oubliettes, and such don't help . Poisons are unreliable because resistance isn't hard to come by.

Well, most kingdoms really couldn't afford the resources necessary to be certain of confining pretty much any high level character. Much less catching one to begin with. Easier to catch a leprechaun in Peru.

[Belac93]

Well, most kingdoms really couldn't afford the resources necessary to be certain of confining pretty much any high level character. Much less catching one to begin with. Easier to catch a leprechaun in Peru.

For most high level opponents, really the only real way to deal with them, is to hire something more powerful. Got problems with a level 13 evoker? You gotta hire a level 14 abjurer.

[Sigreid]

For most high level opponents, really the only real way to deal with them, is to hire something more powerful. Got problems with a level 13 evoker? You gotta hire a level 14 abjurer.

Too much time as a project manager has me immediately thinking that the return on investment would be hard to make work.

[VoltaicVitriol]

In the real world I would restrict the use of their hands and keep snake root in their food. Snake root disables vocal chords (it's also known as the mother in law plant). There could easily be a similar plant in any fantasy world known to herbalists and poisoners.


Are you sure that vocal paralysis is a side effect of snakeroot? I just looked over its toxicology information, and the only thing I saw was milk sickness. And vocal paralysis is not one of the effects. I don't know of any plant-based poison that paralyzes vocal chords. You might be thinking of Dieffenbachias, which can render somebody mute by causing extreme swelling of the tongue lips and gums.


On a related note, you don't even need fantasy Alchemy. A little knowledge of real-world herbalism can lead to some horrifying applications.

[Sigreid]

Are you sure that vocal paralysis is a side effect of snakeroot? I just looked over its toxicology information, and the only thing I saw was milk sickness. And vocal paralysis is not one of the effects. I don't know of any plant-based poison that paralyzes vocal chords. You might be thinking of Dieffenbachias, which can render somebody mute by causing extreme swelling of the tongue lips and gums.


On a related note, you don't even need fantasy Alchemy. A little knowledge of real-world herbalism can lead to some horrifying applications.

It worked on my cat when I was a teenager. We thought he was really quiet until the neighbor's snake root plant he had been eating died, then he was loud all the time. It didn't seem to hurt him in any way.

[VoltaicVitriol]

It worked on my cat when I was a teenager. We thought he was really quiet until the neighbor's snake root plant he had been eating died, then he was loud all the time. It didn't seem to hurt him in any way.



It may have different effect on cats than it does on other animals. It is mildly poisonous to cows and other cattle, and can pass that poison on to humans. In the early to mid eighteen hundreds milk sickness caused by snakeroot contaminated meat and milk was responsible for thousands of deaths across North America. Including the death of Abraham Lincoln's mother. Cats do have a habit of chewing on poisonous plants. No idea why.

[Daishain]

DM fiat is endless. Just as a few examples, you could have:

-A mildly toxic ingested herb that deadens a being's connection to the weave for 24 hours. Difficult to distill and safely administer, making it very difficult to use in the field.
-A series of mildly magic runes that low level NPC Adepts can duplicate. If in full contact with a being for a period of at least one hour, it delivers a nasty shock to the being's system if a spell begins to form. Said runes can be applied to the interior of manacles.
-Natural, if rare, crystals that function as something of white noise generators, interfering with magical vocal components in a very limited area.

Now, it would be best for these methods to be flawed, not least because a truly inescapable prison system is just boring. One potential flaw to insert is that the countermeasure can be beaten with a very difficult concentration check, say DC 25 (with the DC going up with every retry in a short period of time), such that an apprentice has no shot at all, but a gifted low level individual or a master mage has a chance

[Kadzar]

A key thing to remember is that this falls apart at higher levels. Contingency+Freedom of Movement ensures those manacles, oubliettes, and such don't help . Poisons are unreliable because resistance isn't hard to come by.
At first I thought Contingency might be a problem, but the spell requires a statuette worth 1500 gp that must be kept on your person at all times, or the spell ends. Not to say it wouldn't be possible to hide such a thing, but it would be very hard and possibly uncomfortable. Also, the spell goes off the first time the circumstances you specific occur, whether you want it to or not, and then ends.

[Sigreid]

It may have different effect on cats than it does on other animals. It is mildly poisonous to cows and other cattle, and can pass that poison on to humans. In the early to mid eighteen hundreds milk sickness caused by snakeroot contaminated meat and milk was responsible for thousands of deaths across North America. Including the death of Abraham Lincoln's mother. Cats do have a habit of chewing on poisonous plants. No idea why.

Maybe it's an instinctual defense against parasites.

[Ashrym]

Dress him in banded armor. It weighs him down, interferes with spell casting, gives disadvantage on stealth, keeps AC relatively low, and isn't expensive.

Keep hands bound, mouth gagged, and being folded with a bag over the head for backup. No focus, no components, no somatic ability, no verbal ability, no line of sight.

Don't let them know where they are being held and make sure it's deep underground. Make sure that includes a maze, traps, and trained monsters as guards.

Keep them sedated with poison as much as possible.

Don't let them rest. "Interrogation" every 30 minutes. A person doesn't want to risk short or long rest ability. This also works on exhausting them.

No food or water until nearly dead.

Keep an emergency pull switch to completely fill the cell with sand.

Let them know that if they do not cooperate with incarceration that lethal force is the only available alternative or threaten what they hold dear in consequence. Persuasion or intimidation can be used to get them to stay voluntarily.

Things like that might not work universally, but it covers a lot of ground.

[Addaran]

For all those saying to dress the mage in armor, that's not very humane to force someone to wear a 20lbs+ armor on them at all time and sleep in metal....

And i'm pretty sure after a few years of always wearing an armor 24/7, they'll become proficient with it. ;)



Don't let them rest. "Interrogation" every 30 minutes. A person doesn't want to risk short or long rest ability. This also works on exhausting them.


After six(?) days he's dead from exhaustion. So much for long sentences. =(

[Sigreid]

For all those saying to dress the mage in armor, that's not very humane to force someone to wear a 20lbs+ armor on them at all time and sleep in metal....

And i'm pretty sure after a few years of always wearing an armor 24/7, they'll become proficient with it. ;)



After six(?) days he's dead from exhaustion. So much for long sentences. =(

As I understand it after 48 hours or so virtually nothing can keep someone awake.

[Ashrym]

For all those saying to dress the mage in armor, that's not very humane to force someone to wear a 20lbs+ armor on them at all time and sleep in metal....

And i'm pretty sure after a few years of always wearing an armor 24/7, they'll become proficient with it. ;)



After six(?) days he's dead from exhaustion. So much for long sentences. =(

It gets the point across to the prisoner. At that point he or she may be more reasonable about not trying to escape in exchange for better treatment, getting back to persuasion etc.

Could always go back to cutting off feet and hands, cutting out the tongue, and gouging out both eyes as threats as well. Just knowing that's going to happen after getting caught a second time if the caster tries to escape the first time is a deterrent.

The question is less how to keep the caster there and more what might cause compliance in staying. It is a role playing game, after all. ;-)

[Draco4472]

Well, I may have one possible solution. Assuming this spell sorter (http://donjon.bin.sh/5e/spells/) isn't some way in error, there are apparently no spells that have neither somatic nor verbal or both. So if you have a mage both bound and gagged, they won't be able to do anything (unless they're a Sorcerer with Subtle Spell, but I'm not sure anything short of the Imprisonment spell or some sort of permanent antimagic field will stop them).

Or you could just cut out the tongues and cut off the hands of every spellcaster who commits a magic-related crime. Save the police force a lot of their budget, just need to buy a couple good knives.

Sorcerers remain the only problem though.

[RickAllison]

At first I thought Contingency might be a problem, but the spell requires a statuette worth 1500 gp that must be kept on your person at all times, or the spell ends. Not to say it wouldn't be possible to hide such a thing, but it would be very hard and possibly uncomfortable. Also, the spell goes off the first time the circumstances you specific occur, whether you want it to or not, and then ends.

I don't think the cavity search has been invented yet...

[Sigreid]

Realistically, you can keep the ones who decide to be good citizens and not escape. Or you can kill them.

[MasterMercury]

Casting requires complex hand gestures and precise magical words, right? So say I cut 2 fingers off each hand, and break a lot of teeth so they talk with a slur.
Based of Middle Ages, when invading lords would cut one finger off peasants so they couldn't be archers but could still work.

Sorcerers are a problem still, but what can you do?

[RickAllison]

Casting requires complex hand gestures and precise magical words, right? So say I cut 2 fingers off each hand, and break a lot of teeth so they talk with a slur.
Based of Middle Ages, when invading lords would cut one finger off peasants so they couldn't be archers but could still work.

Sorcerers are a problem still, but what can you do?

Was it really that common? I know ear mutilation was fairly common for serious crimes (it was always visible and didn't reduce the utility of the person much), but the only references I find to removing the fingers was by the French to the English. The French did it so that the English archers wouldn't be able to fight as effectively, whereas that would be rather the opposite for what the English would want.

This would be far more important for someone with power like magic. Those would not be people imprisoned in dungeons or mutilated, but instead put into service to the appropriate noble as penance. Just as other nobles were only imprisoned for the use of the ransom/bail money, it makes far more sense to a ruler to have the caster serving him than making a permanent enemy.

Which would you rather have as a ruler: would you like every Mage you capture to hate you for crippling them, or to be a potential ally because they have worked with you? Only a fool would cut off a mage's fingers or remove her ability to speak.

[Belac93]

A Path of the Awakened Mystic would be absolutely terrifying to have to capture. Most of their abilities rely on sight, but then they also have third eye, giving them blindsight out to 30 feet. So you would have to blind them, and then restrain them 30 feet away from anyone else. And the subclass that hasn't been released yet, the one with telekinesis... Even a first level one of those will probably be impossible to capture for a long length of time.

[Spore]

Dress him in banded armor. It weighs him down, interferes with spell casting, gives disadvantage on stealth, keeps AC relatively low, and isn't expensive.

Keep hands bound, mouth gagged, and being folded with a bag over the head for backup. No focus, no components, no somatic ability, no verbal ability, no line of sight.

Don't let them know where they are being held and make sure it's deep underground. Make sure that includes a maze, traps, and trained monsters as guards.

Keep them sedated with poison as much as possible.

Don't let them rest. "Interrogation" every 30 minutes. A person doesn't want to risk short or long rest ability. This also works on exhausting them.

No food or water until nearly dead.

Keep an emergency pull switch to completely fill the cell with sand.

Let them know that if they do not cooperate with incarceration that lethal force is the only available alternative or threaten what they hold dear in consequence. Persuasion or intimidation can be used to get them to stay voluntarily.

Things like that might not work universally, but it covers a lot of ground.

Bro that is not containment. This is highly LE territory. It actually reminds me of several real world facilities where political prisoners are held. I mean it is realistic but I am not sure I want that in my games.

[LordVonDerp]

Well, I may have one possible solution. Assuming this spell sorter (http://donjon.bin.sh/5e/spells/) isn't some way in error, there are apparently no spells that have neither somatic nor verbal or both. So if you have a mage both bound and gagged, they won't be able to do anything (unless they're a Sorcerer with Subtle Spell, but I'm not sure anything short of the Imprisonment spell or some sort of permanent antimagic field will stop them).

However, there is the tricky issue, for long-term confinement, that you probably don't want them dying of starvation. Assuming your world doesn't have feeding tubes or the like, it seems magic will be needed here. This may be one of the few times where the Silence spell being castable as a ritual actually has a use. You can now feed your prisoner without fear, though remember that you have to put the gag back in before the spell runs out.

Alternatively, if you don't want to have to bring a caster in every time you feed your prisoner, Mordenkainen's Private Sanctum can be made permanent, and has the ability to prevent teleportation into or out of it's barrier, among other effects.


Remove their tongues.
Or treat them like honored guests like you would with a high ranking captured enemy.

[RickAllison]

Remove their tongues.
Or treat them like honored guests like you would with a high ranking captured enemy.

The second is how I would see most casters turning out in prison, the first is how I would see proven enemy casters who you are planning to execute would be handled.

Plus, if you treat them with dignity and simply the promise that escape attempts will not be, most would just go along for the ride. Bards would not be a fan, but a wizard likely gets to continue his research and gets the guard as a pseudo servant, a cooperative Druid could probably be relocated to a wooded copse, and a cleric could be "imprisoned" in a church. This also applies to non-magical PCs, as why should a lord sully relations with one of the best archers in the land, or the monk who has stood in the middle of multiple calamities and remained eternally standing?

[Ashrym]

Bro that is not containment. This is highly LE territory. It actually reminds me of several real world facilities where political prisoners are held. I mean it is realistic but I am not sure I want that in my games.

Persuasion isn't LE. There are more and less extreme options.

I would point out that a LG society with a reform system can still have abusive guards, or the mage who is a prisoner can be given a DC 10 history check to realize that's not normal practice as they get marched by such activities but that it happens with prisoners who present problems because that's what the guards are forced to do after prisoners escape and get brought back in.

The threat of those actions as a possibility promote compliance as a response.

[smcmike]

It depends a lot on social context.

Is the mage you are holding a psycho killer? If so, why are you keeping him alive at all? If you really need to hold a mage who is actively seeking to escape and is willing to kill, you will have to be pretty brutal about it. Gags and hoods and shackles exist for a reason. Alternatively, DM fiat environmental factors - cells in spell-dampening rock or whatever.

If he isn't a psycho killer, do you have any leverage? If so, he may just cooperate - if he has hope for peaceful release, that might be better than becoming a fugitive felon. Heck, if he is an actual person embedded in society, there may be things he'd be willing to face eternal improsonment for.

[Zorku]

Since we're talking NPCs it's easy enough to just not give this one poison resistance. The old "this poison has no noticeable effect until you go x minutes without receiving another dose of this poison" trick gives you decent security, especially if none of the prisoners are told that their meals are laced with the stuff. In a similar vein, the eggs of some parasite could be easily enough force fed to a captive, and then they are reliant on you for the substance that stalls growth of the parasite, again, without really filling anyone in on the details. For the most part you could insist either option was a curse, and not inform most of the employees in the area of the details. There are little hints to pick up like how everyone that's not a prisoner has strict rules about not touching particular foodstuffs, etc, but and NPC isn't going to find their way out of a situation where they're deprived of information.

If this is an evil institution then they let somebody break out and get somebody to cast remove curse on them, but the staff just insists that the curse it too powerful to easily remove and that corpse stands as a warning. A more chaotic institution works the same way but they never let someone escape like that and instead they created this as a tall tale... which will turn out true if anybody tries to recreate the conditions.

And again, this isn't for indefinite detention of a PC, but it could feasibly hold an NPC until the PCs show up to break them out.

[MaxWilson]

In the course of fantasy law enforcement, mages would present a particular problem, what with their spells and such being pretty nasty tricks they always have available to try to escape from or harm their captors. So what is a state or other organization supposed to do?

Well, I may have one possible solution. Assuming this spell sorter (http://donjon.bin.sh/5e/spells/) isn't some way in error, there are apparently no spells that have neither somatic nor verbal or both. So if you have a mage both bound and gagged, they won't be able to do anything (unless they're a Sorcerer with Subtle Spell, but I'm not sure anything short of the Imprisonment spell or some sort of permanent antimagic field will stop them).

However, there is the tricky issue, for long-term confinement, that you probably don't want them dying of starvation. Assuming your world doesn't have feeding tubes or the like, it seems magic will be needed here. This may be one of the few times where the Silence spell being castable as a ritual actually has a use. You can now feed your prisoner without fear, though remember that you have to put the gag back in before the spell runs out.

Alternatively, if you don't want to have to bring a caster in every time you feed your prisoner, Mordenkainen's Private Sanctum can be made permanent, and has the ability to prevent teleportation into or out of it's barrier, among other effects. Though that still doesn't stop certain spells like Vicious Mockery or Immolation, but they and many spells like them require you to see your target, so they could be stopped with a blindfold. Spells this won't work for include several purely defensive buffs, Darkness (though this requires a material component, and doesn't do much), Destructive Wave (damaging, but 5th level spell only available to Paladins, Tempest Clerics, and Bards through Magical Secret, of course. Might be kept in check by requirement to strike the ground.), Dissonant Whispers (damaging and only 1st level, but requires the target to hear them, so could be blocked by earmuffs), Glibness (dangerous, dangerous lies), Sword Burst (damaging, but you could maybe feed them with a 10-foot pole, Warding Wind (not really dangerous, but, like Darkness, annoying for anyone who gets near them), Whirlwind (damaging, but requires material component), and Wish (but if you're imprisoning someone someone who can cast Wish, you probably don't want to be taking any chances). And while creatures can't teleport in or out of the sanctum, technically it seems like they could teleport somewhere inside, and I think that that might let them get out of their bonds.

You could maybe also use Hallow (to get permanent silence or anti-teleportation), but the Charisma save makes it not so great.

Does anyone have any other ideas on this subject?

Beat him unconscious. It doesn't take a spell to reduce him to 0 HP.

If you're more civilized than that, just beat him up regularly (to use up any Shield spells) and after you capture him, never allow him to get even a short rest--uncomfortable conditions, never more than thirty minutes' of sleep at a time, etc. He may retain a few spell slots, but they are spell slots which didn't help him avoid capture in the first place.

Basically, treat him like a guest of the Spanish Inquisition.

[Basch]

The Witcher universe has a metal called dimeritium that I use in my games. When forged into shackles it stops the wearer from using magic at all and can be used in bombs to burst into a fine powder, preventing magic use in the affected area, it works well enough for us.