I'm working on a homebrew setting, and came upon the idea for an unusual prison, one specifically for wizards who are judged too dangerous to be allowed to move freely in the world. (I might add other arcane spellcasters, but I think that might be too challenging). This is obviously a very cinematic idea, but I'd like to at least try to make it believable.

Some ideas, in no particular order.

1. Spellbooks, arcane foci and all components locked up. Logically the books should be destroyed, but I imagine this place is run by wizards, who'd have a hard time doing that. The books would be kept under lock and key, protective spells and possibly stored in an extra-dimensional space.

2. No spellbooks means wizards are limited to cantrips (I think?)

3. Prisoner areas have many gems of silence embedded in the walls at twenty foot intervals to negate verbal components.

4. Prisoners have their hands at least partially restrained to prevent somatic components; this might be the hardest part. How do they eat? Do they feed each other with long spoons or something equally bizarre? Are the forced to wear awkward heavy gloves that make delicate gestures impossible?

5. Feats can be very dangerous. Metamagic Adept or other feats might allow some wizards to pull shenanigans even with such security measures. How could these be bypassed?

6. Are some wizards so dangerous that they require specific magic items or higher level spells to contain, like the cryo prison from Demolition Man? 

Any suggestions would be greatly appreciated!

An additional note: my campaign has a somewhat lower level cap on NPCs, similar to Eberron. Most kings and high priests are level 10, and there are very few NPCs close to 15, so higher level wizard features like Spell Mastery and Signature Spell aren't much of an issue.

Wearing armor you are not proficient with negates spellcasting... Mandatory chain mail? Strap a shield to their arm? Some casters would get around this by having the proficiency, but it's another tool in your arsenal...

1. The wizard prisoners would need to be able to get their spelbooks back in an escape. But maybe something like a gargoyle could guard it?

3.  The wizards could also be gagged to stop verbal components.

4. I'de go with magical gloves.

More ideas: I'de have each wizard have two (loyal to the prison heads) guards: A martial and a spellcaster, even at low levels, these guards could be deadly to wizards without their spellbooks. The spellcaster could also keep an eye on the prisoners magical shenanigans (detect magic) and stop them with dispel magic. These guards would also alternate and do daily reports to the people in charge of the prison, about the prisoners.

Permanent Anti-magic field? or make use of a naturally occurring anti-magic area to create a prison?

Other than that, silence, no material components, special heavy gloves that prevent somatic components (maybe lead lined to prevent the manipulation of magic though that requires some work to define exactly how magic works in your game world).

However, at a certain point, you have to determine why the society decided it was so important to invest significant resources in keeping these very dangerous individuals alive. It may go against modern sensibilities but extremely dangerous captives with no other value likely would not have lived that long.

This is especially true if they pose a significant risk to the society and the society can not reasonably prevent outside forces from ever releasing the individual. A D&D world is quite different from the real world in the sense that real power in D&D often stems from the individual capabilities while in the real world, power usually is due to control over an organization. Individually, those in power, aren't that superior (if at all) to most individual members of the organization - the power derives from what they can have the organization do while in D&D games the power often derives from what an individual can do.

A high level wizard is powerful, in and of themselves, and may have an organization that they also control - this can make them far more dangerous to the society than a powerful figure in the real world. As a result, a D&D society needs a really good reason to keep dangerous anti-social wizards imprisoned rather than dead.

First, Wizards only need spellbooks to CHANGE the spells they prepare.  You no longer need to study them every morning, like in old editions.  Nothing short of death, by RAW,  to my knowledge removes a spell from a Wizard's prepared list, except the wizard studying a new one.  (But one could house rule a Modify Memory removes the spell.)

"You can change your list of prepared spells when you finish a long rest. Preparing a new list of wizard spells requires time spent studying your spellbook and memorizing the incantations and gestures you must make to cast the spell: at least 1 minute per spell level for each spell on your list."2

Second, a lot of what you describe is frankly easy to defeat.  There are over 20 spells that do not require verbal or material components, just Somatic ones.  The list includes: the Mold Earth cantrip (which can move stone and earth), Mislead (an invisiblity spell), and Demiplane (which lets them leave your prison and go someplace where they SHOULD have a complete set of spell components and Spellbooks.

Not to mention subclass abilities, which can include things like Shadow Walk and Wildshape.

To imprison 99% of spellcasters I would suggest anti-magic or magic items specifically designed to do this.

If you were trying to just imprison low level wizards,  I would make metal prisons, with metal gauntlets locked to their waste, preventing somatic components, along with silence and the removal of their possessions.

Another way to do it is to use specific spells such as Imprisonment.

But none of these do what you seem to want to do, build a prison for casters.    To do that, the simplest way to do it is to house rule.   Just tell them due to some arcane rituals, any conjuration spell does not work inside the prison.  Then throw in Silence in all the cells, and the are naked except for rags.  This will heavily limit them but still let you run a "prison break" type adventure.

 Also, spellbooks are incredibly valuable.  No sane wizard would ever under any circumstance have a rule of destroying them.  At worst, they might destroy one that had 'forbidden spells'.   Instead they are studied and passed around. But you could rule they only pick them up on Fridays, or something.  That gives them a time limit to escape before then.  The spell books should be locked in a trapped chest till then.

Quote from eapiv >>

Wearing armor you are not proficient with negates spellcasting... Mandatory chain mail? Strap a shield to their arm? Some casters would get around this by having the proficiency, but it's another tool in your arsenal...

Not a bad idea! The idea of suits of mail designed specifically to impair casters is not without merit! What sort of designs and details would they feature? Food for thought!

Oh yeah, I forgot about the armor thing.  Best of all it is not even a somatic thing, armor prevents all casting, even verbal only.  Good call.

I would make a special kind of armor designed for prison:

Prison Armor, Heavy:  costs 10 gp, AC: 12, Strength requirement of 20 (to negate speed reduction by 10), Disadvantage on Stealth, weighs 80 lbs. weighs only 40 lbs but almost all at your legs and arms (hence the strength requirement and the low AC).

Prison armor has metal loops at the legs, waist, arms, and neck for chains and locks.  It is a skirt/kilt like arrangement, allowing for sanitary uses without removing the armor.   It comes with a 'helmet' and 'gauntlets'.  The helmet, when worn, gags the wearer, preventing speech and verbal spell casting, but does allow one to drink liquids, including soup.   The gauntlets, only allow you to move your thumb, thereby preventing any somatic components even if you are proficient with Heavy Armor. But one can still awkwardly grab things, such as spoons, blankets, etc.

Even this will not stop a caster that has Heavy armor proficiency and the Metamagic Subtle spell from casting.  So it will not work on Fighter 1/Sorceror 3  (or people with the right feats).    But that is something I am much more comfortable accepting.  It will defeat the far majority of spellcasters. 

Easiest might be a homebrew item that’s says while you are wearing it, you are unable to cast spells or use any class abilities. Have it welded around their neck, so if one of them is an AT rogue, they can’t just pick the lock. You have to nix the class abilities, or sorcerers with the right metamagic can still cast, and warlocks with the right invocations can still pull things off. And an artificer could make the tools they need to break the weld. And then there’s the shenanigans any of them could pull off with a familiar, ugh, so they’ll be sure to kill any familiar the caster might have.
And just to be extra careful, there can’t be any windows or anything which allows a line of sight to the outside. Probably not even a door. They just teleport in and out. Not with a portal, because that would be too easy for someone to escape through. Someone casts the spell. Or maybe a helm of teleportation, which is kept outside. At a shift change, one guard uses it to go in, and another uses it to go back out.

Assuming something 'low tech' then any form of physical restraint or punishment (such as broken fingers, manacles or strait jackets) to limit or remove the ability to perform somatic compnents, combined with some form of sleep deprivation (to limit spell slot regeneration) and overwhelming physical force (such as 5 gaurds to 1 Wizard) should cover it. Speaking without being given permission could be punished in numerous ways.

If you wanted something more high magic then the best option would be a warden such as a Beholder and have Spectators as guards. Another option would be to pinch the Collar of Khorne from Warhammer (the Games Workshop universe) which effectively prevents the wearer from casting any spell.

But, having said all that, the one I would probably drift towrds is have anyone sentenced to go there is cursed so that anytime they try to cast/use a spell they instead enter a Rage as per Barbarian, think of it as a magical labotomy.

I thought about sleep, but that kills you from exhaustion.    The real problem is the game is focused on adventuring and spellcasting is an essential part of adventuring.  As such they have avoided things that totally prevent spell casting.

That said, the curse idea is interesting, but it already exists.  It is called FEEBLEMIND.  8th level spell that prevents casting, though you do get a save immediately and once again every 30 days.  But that screws with normal role playing as you Int and Charisma drop to 1, etc. etc.

One could also just make a cursed ring that prevents spell casting.    Simple, cheap magic item that does what you want.  To remove it you need a Remove Curse spell.

If the prison-keepers are really serious about this, then they cut off the wizards' hands and remove their tongues. No more verbal or somatic components. That just leaves getting rid of material components, so no arcane foci, components, or spell books should be kept on-site, including by any of the guards or staff. It would be crazy if there was somewhere they can get hold of them. In a world where there are whole prisons for wizards (and it's not just one guy being entombed in a cave), there will be spellcasters who can cast regeneration spells to restore the lost tongue and hands if they decide that the wizard should be allowed out.

You need a good reason to determine why the wizards are being imprisoned this way. If they are never going to be released, then they should just be executed instead; prisons are very expensive to run, and in pre-modern periods the inmates relied on other people bringing them food and stuff or they just died of disease and starvation. So you need a convincing reason to imprison them (e.g. the society is run by a holy order who follow the Way of Mercy or some such).

Keeping creatures with anti-magic abilities could be useful. One option might be to keep some caged intellect devourers that the prisoners are exposed to for just long enough for their intelligence to be reduced to 0, then leave them that way.

Why not just have the wizards wear collars enchanted with antimagic field?

Or just put a geas on them for the duration of their sentences?

I remember that there was some prison in official lore that held extremely dangerous prisoners by petrifying them. Hire a medusa to have a staring contest with the wizards and store them indefinitely.

I believe that Intelligence and other stats recover at a rate of 1/day unless magic prevents it. An intellect devourer sounds nice, but it would require daily use combined with protection from evil/good to prevent the devourer from killing.

Petrification makes for a good way to store wizards.  Not that punative (as they do not remember the time spent), not rehabilatory, but it can store them.  I could see a country doing this as a kind of Suicide Squad type thing.  You petrify criminal wizards, than unpetrify them in a war or similar situation, offering them the chance to earn their freedom in exchange for highly dangerous activities. 

Yeah, petrification is purely deterrence. It's also handy in the case of an evil lich, if you don't have their phylactery, in which case killing them would just cause them to reform somewhere unknown.

Some great ideas here! It might take me a while to respond to everything.

A few points:

1. This is a prison run by wizards, for wizards; no sorcerers, warlocks or other spellcasters inside. Wizards are something of their own social order in this setting, and are very reluctant to kill a fellow wizard outright, as they tend to be very lawful and ultimately hope to turn their brethren back onto a productive path. They police their own.

(Yes, I used to play Ars Magica; why do you ask?)

2. My idea for this location is for the players to help break someone OUT, but not let the real psychos loose. It also demonstrates how wizards are different from other casters.

3. The most powerful NPCs in my campaign top out at level 15. There are a *handful*, maybe one of each class, that sit at 20, and they tend to be the focus of quests. 9th level magic is exceedingly rare, but does exist.

4. The Spire of Thoth (as it's called) is a narrow needle about 30 feet in diameter and maybe 80 feet high(?); it can hold up to 30 magi, but currently only holds 10. It's out in the middle of the Great Desert, and it looks like it's carved out of bone.

5. Spellbooks are NEVER destroyed, unless cursed or something; they're just too valuable. They are often hidden in out the way places, though.

We have something to this effect in the game I am running. Evil wizards of great power are contained in a long-term Soul Cage that is ritual cast as part of the execution of their mortal body. The disembodied souls are then archived.

During intake you are thrust in an anti magic field to dispel any hidden magic, every single prisoner has hair and blood samples taken for scrying. the less behaved ones have the hall a room enchanted with frustrating background noise that only allows short rests, all tattoos and body markings are surgically cut off. A area of magical darkness guarded by a devil. 

so problem wizards, order of the scribe, conjugation, illusion mages. Each of these have problem at different levels. Conjugation must be kept magical darkness room so they never see a key. Transmutation wizards are checked up on ever 20 mins. Illusionist at level 14 MUST be induced to a coma for the whole sentence.

if we have any reason to believe you have the keen mind feat you are kept in solitary for a month with very regular checks

Quote from Mog_Dracov >>

Oh yeah, I forgot about the armor thing.  Best of all it is not even a somatic thing, armor prevents all casting, even verbal only.  Good call.

I would make a special kind of armor designed for prison:

Prison Armor, Heavy:  costs 10 gp, AC: 12, Strength requirement of 20 (to negate speed reduction by 10), Disadvantage on Stealth, weighs 80 lbs. weighs only 40 lbs but almost all at your legs and arms (hence the strength requirement and the low AC).

Prison armor has metal loops at the legs, waist, arms, and neck for chains and locks.  It is a skirt/kilt like arrangement, allowing for sanitary uses without removing the armor.   It comes with a 'helmet' and 'gauntlets'.  The helmet, when worn, gags the wearer, preventing speech and verbal spell casting, but does allow one to drink liquids, including soup.   The gauntlets, only allow you to move your thumb, thereby preventing any somatic components even if you are proficient with Heavy Armor. But one can still awkwardly grab things, such as spoons, blankets, etc.

 

Even this will not stop a caster that has Heavy armor proficiency and the Metamagic Subtle spell from casting.  So it will not work on Fighter 1/Sorceror 3  (or people with the right feats).    But that is something I am much more comfortable accepting.  It will defeat the far majority of spellcasters. 

I love the prison armor so much! Definitely swiping that!

I am not a huge fan of multiclassing; I of course allow my players to do it, because I'm not a monster, but in general I tend to make more of my NPCs single class. This goofy bias on my part let's this idea work better, as all the wizards in the Spire are single class. This is also due to the intellectual snobbery of 'hermetic casters' (wizards), who feel studying magic out of spellbooks is superior to all other forms of magic. This allows non-wizard PCs to rub their sorcery and pact magic in their stupid faces to prove them wrong!