# How can I imprison a wizard who can walk through walls?

There are reasons why we can't walk through walls. Using magic, though, those difficulties fall away. In fact, for a wizard in an otherwise-almost-magic-free world, walking through walls or falling through floors is an ability he can harness on cue.

The wizard has used his powers for evil, though, and after a long war against him and his armies, he has been defeated. The victorious army wants to keep him alive but imprison him. They quickly realize that this is a very hard thing to do, as he quickly runs out of a normal prison cell. In fact, they discover that he can escape from anything - ropes, handcuffs, etc. They only manage to move him from one place to another by constantly sedating him.

How can they imprison the wizard without keeping him unconscious all the time? They only have medieval technology, though, so their options are quite limited.

They want to imprison the wizard somewhere on the planet they live on, which is earth-like.

• He can pass through anything, but he has to hold his breath.
• He can designate an area of ground where he will not fall through at a given point in time.
• He can't fly; most of his other abilities are unknown, but he cannot transform some materials into others. It seems that there's nothing else he can use to escape.
• There are no other known wizards.

The army want to put him somewhere where

• He cannot escape
• He can survive with food and water periodically given to him, and with a source of air (and ventilation)
• High-level officers can interrogate him

This location must be somewhere on land, and must either be a natural feature or be buildable by medieval technology. This means that he can't be put in water, outer space, etc. (fortunately, these have not been suggested by anyone).

• I don't often put questions on hold by mod-hammer, but with all the back and forth going on and answers seemingly becoming invalidated by edits to the question after the answers have been posted, it seems clear to me that this question needs some work before it is really a good fit for our Q&A format. Please take the discussions to chat (see link in the above comment), fix the question according to what those discussions turn into, notify the posters of all existing answers of those edits with a comment each, and then reopen the question (assuming it can be turned into a good question). – a CVn Mar 23 '15 at 20:52
• In light of the fact the question has been updated with all relevant facts and the transmutation has been de-added I've reopened the question :) – Tim B Mar 23 '15 at 21:16
• What are the powers he used for evil and what keeps them from being used while he's conscious? – Mazura Mar 24 '15 at 4:37
• @Mew "Ultrahot lasers" would seem to fail the "medieval technology only" constraint. – a CVn Mar 24 '15 at 8:11
• @Jimnosperm He can designate an area of ground where he will not fall through at a given point in time, meaning he could essentially pass through the wall of the hole and ascend the blocked area with stair-like movements. – DoubleDouble Mar 24 '15 at 19:59

Keep him deep underground.

The fact that he needs to hold his breath means he has a limited travel distance. Take a guess on how far he can run while holding his breath, then double it, and put that much stone between him and his next breath.

You indicated that he can not fall through stone by deciding it, but can he climb virtual stairs inside solid rock? He may not be able to even climb out of a deep hole. If he can, just factor sprinting-up-stairs-while-holding-breath distance into the depth of the prison.

Visitation

How do you get into this cell to interrogate and feed him? Clearly any tunnel into this cell (or any of the other answers) would give him a place to run to. But it's easy, just use a long series of thin pocket doors. When the doors are closed the gaps between them and spaces which they will slide into for opening aren't wide enough for him to stand in and take a breath. As the guards come to feed or interrogate him they can open the doors and close them behind themselves.

Depiction of pocket-door arrangement, not to scale.

Alternatively, the surrounding material may not need to be solid rock, but simply any matrix of material too dense for re-materializing. Dense branches or a large volume of barbed wire wouldn't allow enough open air space to materialize in without catching a branch or wire in the gut.

A combination of this and the stone prison could be used, really you could keep this guy in place with a regular jail cell and a whole bunch of bales of hay. Or even a jail cell in the center of a corn field.

• The words. My mouth. You took them out. +1! – Aify Mar 23 '15 at 17:20
• I thought of a problem (though it depends on the phasing ability). Assuming he can partially phase through things (which seems reasonable) won't he be able to stick his head out of the walls as he goes up, and get a breath? You say the pocket door gaps aren't wide enough to stand in, but he would only have to have room for his mouth to get a breath in. It seems like they would have to be essentially airtight, or else be somehow deoxygenated. – sumelic Mar 24 '15 at 7:33
• I think the same door arrangement would work if the prison was in a tower, only with no thick walls needed since he can't fly – Tymric Mar 24 '15 at 13:05
• Even when I was being annoying with the transmutation, this was my favorite answer. – HDE 226868 Mar 24 '15 at 14:56
• @sumelic Going from the description of the power: "He can pass through anything, but he has to hold his breath". This means, to me, if he's passing through something he has to hold his breath. It seems pretty clear that while any part of him is passing through something, he can't breathe. Which implies a whole body on/off sort of spell. – Samuel Mar 24 '15 at 20:31

Why is everyone always over-complicating things?

Step 1) Use a regular room, with a normal, possibly unlocked door.
Step 2) Sever the evil wizard's Achilles tendons.

• Now thats evil... What happens if the wizard knows how to walk with his hands ? – Jorge Aldo Mar 24 '15 at 4:19
• The burghers get a free circus act, before some kind soul picks up the luckless wizard and takes him back to his hut. – Serban Tanasa Mar 24 '15 at 4:27
• Can't argue with the simplicity; it reminds me of the movie Misery. Also this is probably a whole lot more satisfying for the captors. – Samuel Mar 24 '15 at 16:57
• @tepples I suppose you could sever his spine. Paralyze him from the neck down. – DoubleDouble Mar 24 '15 at 19:25
• @JasonC A very good point. I'm conflating too many crippled blacksmiths. – Alchymist Mar 25 '15 at 15:49

Since he can't fly they could just hang him in a cage over a very deep pit. They could still drop food and water from above to feed him but any escape attempt would result in a deadly fall.

• Cover the rope in broken glass so that even if he phases through the cage he won't be able to climb, – SF. Mar 24 '15 at 10:34
• Good point. There shoud be also some guards to watch for potential escape attempt. – Januson Mar 24 '15 at 11:26
• By far the easiest solution to implement. – Nit Mar 26 '15 at 14:19
• @SF If he can choose which surfaces hold him and which surfaces don't, broken glass wouldn't be much of a deterrent, as he could grasp the rope below the surface. Instead, use a host of separated, tiny filaments, each one too small to hold or support any significant weight, and arranged such that there is no way he could use many of them at once to create a multi-point step. – ErikE Mar 26 '15 at 19:38
• @trlkly I thought he has to hold his breath only while he is inside the wall for example. – Januson Mar 27 '15 at 7:30

An island prison

There are three options here:

1) Strand him on an island. All you need is an island that is about 1/3 to 1/2 a mile from any mainland. This would ensure that he couldn't pass through the ground and make it back to fresh air in time.

2) Build a floating prison (read: boat), anchored to the bottom of the sea. This doesn't need to be so far off the coast as a regular island. His only option is to swim. Guards on the coast should be able to see him coming, and use whatever means they used previously to capture him.

3) If you want to be extra safe, place him in a submerged cell - a cofferdam. Note this would probably be impractical, time-consuming, and expensive, but it would be completely awesome. How to achieve this using medieval tech:

• Drive a series of long wooden stakes into a lakebed, to form a circle. Keep each stake tightly touching the one next to it.
• Drive another series of stakes to form another circle, enclosing the first, about a half-foot further out. Now you have two concentric circles of stakes.
• Pour a clay mortar mixture into the space between the stake circles. This sinks to the bottom and displaces the water.
• Remove the water from inside the the clay walls by pump or bucket.
• Now the inside of the cofferdam should be relatively dry, and you can climb down and reach the lakebed. Create a stable foundation, and line the inside with stone, mortar, and pitch, to reinforce and waterproof.

Note: this explanation came pretty much directly from the book World Without End, by Ken Follett. If there are issues with doing this as I've described in the Middle Ages, take it up with him.

Now throw the wizard down in the water cell. You can cover the top, or not, it's irrelevant. For all he knows, he's been thrown into a regular well. Imagine his surprise when he tries to walk through the walls and instead of dirt, he finds he's surrounded by water - complete with spikes/traps/crocodiles/sharks with laser beams. Your guards can resupply him periodically, just boat out to the cofferdam cell and throw down what he needs.

• He cant, he has to hold breath. Passing large ammounts of land or water is the same thing for him, but, he woud suffocate if he has to move a large portion. So, simply lock him on a distant island without resources to build a ship and then visit the island periodically to provide water and food for him. – Jorge Aldo Mar 23 '15 at 16:55
• I'd say don't even provide him food. He can make his own food and water. Station some archers nearby so that they can pierce any balloon he tries to make to float away. – Seth Mar 23 '15 at 16:58
• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:02
• Oh YEAH! Finally a use for sharks with frickin' laser beams! – Peter Wone Mar 24 '15 at 11:18
• @IsaacKotlicky They certainly could build waterproof structures in medieval times: stone, mortar, and pitch. Hydraulic mortar was used by ancient Greeks and Romans (although, ironically, the mortar used during the Dark Ages was not as good as the ancient Romans). The book World Without End by Ken Follett gives a very detailed description of building a watertight structure underwater in 1300s England. Also a floating prison doesn't seem beyond reason. They had boats. They could forge steel chains. It doesn't need to be anchored in the deep sea. – Seth Mar 24 '15 at 16:15

It might take a little creativity to set one up using only medieval technology but I think that all of the base components are available including black-powder, springs and flint, so...

Build your prison like an inverted land mine. The center of the floor is a pressure plate which gets armed as soon as the wizard is placed upon it. The walls and ceiling are all out of reach and are composed of loose steel pellets packed in explosive black powder, surrounded by several feet of solid rock. As long as the wizard lies, sits or stands in the center of the room, the pressure plate stays depressed and nothing blows up. As soon as he approaches any of the walls, or changes the nature of the floor, or phases into the floor, or floats up on a bag of helium, his weight leaves the pressure plate and everything goes boom!

Even if he is out of phase when it blows, millions of ball bearings will ricochet through his unsubstantial body for some time. It will be quite a while before the danger passes and the smoke clears. ...and all that time, the wizard will have to keep holding his breath and casting.

If you were the wizard, how certain of your breath control, casting ability and concentration would you have to be, to even consider trying to break out of a prison like that?

-- simplifying to accommodate non-transforming wizard and the need for feedings, fresh-air and interrogations --

Removing the transformation abilities probably simplified a lot of the other answers, but it leaves this one pretty much unchanged. He can no longer fly or change the walls/floor, but those abilities were handled by the same pressure switch trigger which handled is other magical skills.

Fresh air could be provided by a few small vents in the ceiling, each with multiple steel grates to keep the ball bearings from leaving the prison during a blast. Food and water can be lowered on a rope through the vent directly above the center of the room with empty plates and cups pulled back up after every meal. A pale can similarly be provided for removing his waste products.

Care would be have to be take to insure that he is not fed more than the weight of the waste products removed so that he doesn't inadvertently set off the bomb through weight loss or gain.

Interrogation would have to be handled through the vents with the high-ranking officials wearing armor just in case a stray ball bearing makes it past the grates. Given the tension of being surrounded by a 360 degree claymore mine, I doubt that torture or other motivations will be needed to get the wizard talking.

• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:03
• Before getting rid of the transmutation ability, this answer would not have worked: The wizard could simply have transmuted the explosives into something that cannot explode before proceeding to leave the prison. – celtschk Mar 23 '15 at 23:55
• At what range did his (now absent) transmutation ability work? I assumed he had to be touching a thing to change it, so I put all the explosives beyond reach of anyone standing on the pressure plate. – Henry Taylor Mar 24 '15 at 2:38
• Even if the transmutation were touch-based, the wizard could still escape. He slowly transmutes some air into stone, holding down the pressure plate. At the same time, he transmutes other air into a helium balloon, reducing the wait that he places on the pressure plate. It is the Indiana Jones swap in slow motion. – Eldritch Cheese Mar 24 '15 at 14:28

Build a tower and put him on the top - Best. Prison. Ever. But beware, do not make the tower without a roof, since we know, how Gandalf The Grey escaped

Alternatively: Put him deep underground. in well maybe. It is nice, that you can walk through the walls, but if there is rock only around you and bonus, you do not know where actually you are? Easy

How to feed him?

Tower: Give him rope good enough to go into middle. Give him food into some place in the middle of tower, where you get using really tall ladder. If he wants food, he has to put his rope up and wait.

Well is better, because you can simply throw bread down and there will be always some water.

• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:03

You haven't mentioned that he has any healing powers or that he can move material with telekinesis. All his escaping seems dependent on his ability to walk or run from the prison. My solution is as follows:

1. Gather your best medical professionals
2. Amputate his arms and legs as close to the shoulder / hip joints as possible
3. Lock him in any prison with thick walls and where "straight down" is not an escape route
4. Wish him the best of luck in rolling through the walls at a high enough speed to not need a breath

Of course, this depends on your ability to cauterize and sterilize wounds so the patient doesn't simply bleed out or die of infection. You're able to keep him sedated so that should help immensely with the surgery. However, medieval amputations were still risky business.

• That's almost exactly what I was going to suggest. The available solutions have been constrained down to the point there isn't much left to work with. – Tim B Mar 23 '15 at 18:54
• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:02
• An answer to one of my own questions mentions Nick Vujicic, whose demonstrated ability to thrive without arms and legs might make your answer not the strongest. – Damian Yerrick Mar 23 '15 at 23:27
• Thats evil to the point where we can ask if that wizard is the true evil one :P – Jorge Aldo Mar 24 '15 at 1:59
• @JorgeAldo Well, he started it. – Engineer Toast Mar 24 '15 at 2:13

If the wizard is otherwise affected by normal physics when they walk through walls, you can use a pulley system to hoist them in a cage or room far above hazardous ground. If they phase to escape, the fall and hazard would at least would cripple them if not kill outright. When you need them, you can place a platform over the spikes/moat/what have you and lower them down.

All achievable with medieval tech.

The rope and pulleys could be fashioned in such a way that climbing it would be arduous (forty feet up without a handhold) and either:

• difficult (far too smooth for the human hand) or
• very painful (thorny, rough, etc.).

He's a wizard, not a body-builder or soldier, so it's easier to make it likely that he would fall/fail in climbing the rope. Make it too risky to climb and it becomes an unattractive option.

One could also add guards with crossbows as "deterrent" - climb the rope and we shoot your legs.

• @HDE226868 Answered that in my edit... :) – Isaac Kotlicky Mar 23 '15 at 15:42
• @HDE226868 Well, an arrow would do short work on any balloon... – Isaac Kotlicky Mar 23 '15 at 15:57
• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:04

The answers I've seen have all been about constructing an exotic prison, but I see a much simpler solution. My solution requires an understanding of how the wizard uses his magic. If he needs to speak to cast spells, cut out his tongue. If you want to interrogate him, use paper and pencil. If he has to wave his hands/fingers in complex motions, cut off his hands. The most difficult problem is if he can use magic just by thinking about it, you're going to need something exotic.

Since he can transmute any substance into any other substance of the same state, you'll need a vacuum. After all, he can convert magma to solid rock so he suffers no heat harm from it and water to liquid helium which will evaporate instantly (either that or freeze him alive before it converts to a gas). The only thing he can't work with as you've described him is nothing.

The real problem for an exotic prison is that, without magic, they're fairly impossible to build. Since he's the only known wizard, you're limited to either mundane prisons he can easily escape from or natural wonders involving deep pits.

• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:02
• What if people don't know how the wizard uses his powers? – Arturo Torres Sánchez Mar 25 '15 at 2:48
• @ArturoTorresSánchez Personally, I would recommend killing him, rather than capturing him, but the OP wants to confine him. Having only one individual with magical power in the world is a dangerous affair guaranteed to cause more trouble down the road. – Frostfyre Mar 25 '15 at 3:37

Find his best friends and family and keep them as hostages. That's a common ploy for taming superheroes.

• That's the solution which sounds the best : to retain the wizard on his own will, by fear of something worth happening if he doesn't obey. The advantage of this technic is tht you can make the wizard do whatever you want, you don't have to detain him in a cell, he can work for you. – Vincent Mar 26 '15 at 2:57
• This has the advantage of possibly making your wizard a more complex, relatable character, and allowing relationship dynamics with his captors to transmute, if he is as clever with psychology as with magic. Which is good for your plot. As long as you're okay with the added drama. – Mary C Jun 12 '18 at 23:18

Hang him by his ankles with cuffs connected over a beam.

As soon as he releases one foot he plummets to his death.

• I think the "bag o' helium" trick that OP edited in might negate this answer. Excellent thought, though. I like the "suspended in a giant room and the only way out is up" solution. – Engineer Toast Mar 23 '15 at 18:55
• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:03
• Holding him upside down would make him black out and die pretty quickly from the blood flowing to his head (his heart would have a hard time pulling it back up to get it oxygenated). Eventually his legs would become necrotic similar to those with diabetes induced circulation problems. – Isaac Kotlicky Mar 24 '15 at 13:22

The answer is actually rather simple.

Build a tall tower, as tall as you can. Place a long metal pole sticking out of one side of the tower, as far out as you can. At the end of the pole, hang a tiny platform, capable of supporting only one man, and made of the thinnest materials possible; a wire net, for instance. Construct a system of pulleys and springs that hold the pole; if it gets too heavy or too light, the system fires the pole out and away from the tower, into open air.

The fall through the air will kill the wizard; regardless of what gas he changes the air to, he will still fall through it, and regardless of what solid he changes the ground into, he will still splat when he hits it. The pole and the net will be thin enough that he wouldn't be able to use them to construct a balloon, and he won't have any other materials (say, for example, clothing) to use. He can't climb back towards the tower, or the system will drop him. He can't collect material to use in an escape, or the system will drop him. However, communication is simple, as you only have to yell across empty air. Food and water can be tossed over by unsympathetic guards, who can also trigger the insta-drop by hand, if need be.

Edit:

As an added security measure, the net should be supported by two ropes, held apart at the top. Each rope should be able to support 75% of the wizard's weight without breaking. Together, the ropes will hold the wizard and the net, but if the wizard tries to climb one of them, it will break, which will cause the second rope to also break, which will drop the wizard to his doom.

• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:04

# A ring of fire

Anyone can walk through a ring of fire, but he'll still come out extra crispy. Will require a lot of fuel to keep all that fire going, but since there's only wizard, they can probably afford it.

If you want to keep him from getting out through the floor and roof, light fires there as well.

An an added bonus, it'll be hot as hell in his cell, so maybe after a while he'll agree to play nice and stay put in return for you putting out the flames.

Alternatively:

# Lots of archers

Combined with "that's enough shenanigans, the next time you try to escape, we'll turn you into a porcupine". Assuming the wizard is not suicidal, he'll probably realise that if he leaves people no choice, they will eventually just shoot him and get it over with.

• If he can transmute anything to anything else, he could change the oxygen at the fire to any other non-flammable gas. – Seth Mar 23 '15 at 16:01
• If he can transmute oxygen to other gases, I don't think they're going to capture him in the first place. Medieval men wouldn't stand a chance. – Erik Mar 23 '15 at 16:03
• @Erik Your "blunt trauma" idea (deleted answer) could work. – HDE 226868 Mar 23 '15 at 17:28
• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:03
• Unless you have a very deep ring of fire, he could just step down under ground (since he can walk through dirt, and can designate areas he can step on to create virtual "stairs") to get past the fire ring and then pop up on the other side to escape. – Johnny Mar 23 '15 at 22:05

You just need thick walls.

Why?

He can pass through anything, but he has to hold his breath.

[Comments]: [ArtOfCode]: How fast can he move when passing through things?
[HDE226868]: @ArtOfCode No faster than a normal human could if the things weren't there.

The world record for breath-holding is 20 minutes 21 seconds. However, not only will he be walking (or running) while trying to escape, but likely he's not the holder of that record. Most normal people can only hold their breath for around 2 minutes. Although that figure would be reduced with physical exertion, I'll leave it at that for simplicity and cell security.

Usain Bolt runs at nearly 15m/s (~30mph). Again, our wizard is likely not him. Most normal people run at around 7-8m/s, 16.5-18mph.

That means, in 2 minutes, an average person can run 960m. That's a lot. This figure does get reduced, however, since this wizard isn't breathing; assuming a quadratic reduction of his speed per unit distance, we get a figure around 450m.

Still, building walls that thick is impractical, but there are ready-made walls you can use: underground. Imprison him deep in the Earth's crust and fill up your access holes with cement. If you give these people access to more advanced technology, you can install a video link and microphones for communication.

• Not seeing much difference here from my own answer. I don't think an average person could run almost a kilometer in two minutes while breathing, let alone while holding their breath. Might want to check that figure. – Samuel Mar 23 '15 at 18:22
• They won't be able to install a video link and microphones with medieval tech. – Brilliand Mar 23 '15 at 18:31
• The current world record for running 1km is 2:11 for men and 2:28 for women. – Peteris Mar 23 '15 at 18:46
• @All: edited for those points – ArtOfCode Mar 23 '15 at 20:35
• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:03

I wonder if something like the setup they had for Magneto would work... a room suspended over lava/spikes/acid with the only entrance through the ceiling.

I would build it like this. Take a deep, wide shaft. Line the bottom with spikes if lava isn't available. Build a room with no doors or windows, just a hole in the ceiling. Connect a heavy chain to the top of the room, and hook it to a windlass, which is suspended over the pit. Put the wizard inside the room, and then lower it deep into the pit. Throw food down into the pit through the hole in the ceiling. If the wizard tries to walk through the wall, he'll fall and die, same for the floor.
At this point the only worry is the wizard trying to climb the chain, but a guard at the top pours oil down the chain every day, and trip lines have been strung at intervals. If the wizard tries to climb he'll trip the lines, and the guard can cut the chain, or set it on fire...

Edit
Ok, new idea, no prison can hold this guy, you've made him too powerful, so instead imprison him inside his own mind. Give him a lobotomy or some similar treatment. He's still alive, but doesn't know who or what he is or what he can do. Now you can put him in a nice comfortable normal dungeon.

Edit 2
So you need information from him, so a lobotomy might not be the best idea, as the information might be lost.
You need him to talk about what he knows, so sensory deprivation. Guards have really short shifts, 30 minutes max so that they don't get distracted, but there is no talking allowed. A water pipe is rigged to allow irregular dripping down onto his prison. Not a steady pattern, so that the prisoner can't get used to it. Sometimes the dripping stops completely, but not for long. It's also his water source, so he'll love it and dread the sound of it at the same time.

Edit 3
With transmuting out of the way, I think my answer stands, though now the shaft can be smaller. It can either be a natural cavern, or left over from a mining project. I has to be wide enough that he can't jump from the platform to the wall, so maybe 40 feet wide, which would give 15 feet of clearance between the platform (10x10) and the the walls. If it's left over from a mine, a shaft several hundred feet deep would be very easy. It would have been the shaft used to haul cars of ore up, so it would already have a windlass at the top. Food could be dropped or lowered by rope, and when they want to question him all they would have to do is raise the platform a bit if they wanted to. Being a cavern/mine, they wouldn't need to get him that close to the top to talk to each other, and wouldn't want him to get to close anyway, in case he has some offensive magic they haven't seen.

• Then don't use acid. The comments about transmuting materials weren't there when I started typing this :) Spikes would be better anyway, since a stone spike would kill as easily as a metal spike... Does his transmutation ability have a range? Even if it doesn't, just having the room high enough above the floor would still kill him. The shaft is 1000 feet deep, 200 yards across. and the room is 300 feet down the shaft. He can't jump 100 yards to the walls, and if he falls 700 feet he'll die spikes or no spikes. – AndyD273 Mar 23 '15 at 15:42
• The only comment was the one about the island when I started. Be that as it may, helium gas isn't going to bother much with fabric. It leaks out through the microscopic holes in balloons. That's why helium balloons stop floating. There might be a way around that too. Archers would make a balloon have trouble. Build the room so that if any part of it is removed it will fall apart. And the wizard is put in naked. – AndyD273 Mar 23 '15 at 15:54
• Serious question, is there a reason they are keeping him alive? – AndyD273 Mar 23 '15 at 15:57
• As I told Erik, he holds valuable information as to the location of a weapon. – HDE 226868 Mar 23 '15 at 17:47
• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:02

How's his tolerance to heat? Can you keep him in a dungeon surrounded by a moat of hot water or oil? He may be able to walk through the walls of the dungeon, but may not be able to withstand being boiled alive by the moat. Making the ceiling smooth means that even if he can float up to the ceiling with his magical helium balloon, he won't be able to get a handhold to let him climb through the ceiling - the balloon will just bump up against the ceiling - though it's unlikely that his clothes would contain enough fabric to make such a balloon, it would have to be quite large.

Putting the boiling water under the chamber as well too might make the floors too hot for habitation, so just leave it hollow underneath and let him know that if he tries to transform the thick stone floor to dirt and tunnel out, the guards will flood the underside of the chamber with boiling water as well.

• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:04
• He has normal tolerance to heat. – HDE 226868 Mar 25 '15 at 23:17

SOLUTION 1:
The walls, the door, the floor and the ceiling contain vacuum, either by large portions or numerous small areas. The wizard can not traverse vacuum because the inside pressure of his body will blow off his vines.

SOLUTION 2:
The walls, the door, the floor and the ceiling contain liquid Hydrogen, either by large portions or numerous small areas. The wizard can not traverse liquid Hydrogen because his body parts and muscles will cease to function when frozen.

Of course, we are talking about advanced medieval technology, the one when some have "magical" powers and sedating drugs are perfectly well processed so not to kill the patient.

Also, the fellow alien civilization colleagues of the wizard must not know where their pal is locates so they can not extract him with teleportation means, as they hunt him for his intrusion in other civilizations history without official contact.

Maybe his powers looks magical for us, Terrains (and the people from that Earth-type planet), but, in fact, we just do not have the technology to take advantage of the fact that the matter is only 1/1^18 of the volume is occupying.

But, hey, luckily quantum physics is the same either in vacuum and close to 0°K.

• How could this medieval society create a vacuum? – HDE 226868 Mar 24 '15 at 20:09
• Well, a medieval society from another planet can't be compared with the one from Earth, as OP stated. A planet where wizards really exist should have some technological means to control the energy. As a law of progression says, any new knowledge is based on current knowledge, so, in order for a real wizard to exist, some degree of technology must exist. – Tinel Barb Mar 25 '15 at 9:38
• Of course, if the wizard is an alien from another planet and brought some advanced technology with it and that technology is way too far from current development of that planet, then the military are hopeless overwhelmed and need 1000 feet thick walls and door. – Tinel Barb Mar 25 '15 at 9:46
• People can survive short periods in a vacuum. This article suggests that a human can survive up to 90 seconds before death, though it's not clear how mobile he'll be up to that point. The question was quite clear about using only Medieval technology so liquid hydrogen is not possible, and even making a hard vacuum in a large chamber is likely impossible. – Johnny Mar 25 '15 at 18:54
• @Johnny: "Unconsciousness is likely to occur within 14 seconds". Anyway, It's an invented planet, you can't create a story "Humans vs. Ghosts" without giving humans weapons to fight ghosts. if so, only "Holly Cross" and "Holly Garlic" are the weapons. – Tinel Barb Mar 26 '15 at 11:22

This feels a lot like https://xkcd.com/538/ with some
“Fixed fortifications are a monument to the stupidity of man.” ~ George S Patton
mixed in.

It's very difficult to design a cell such that a non-wizard can't ever break out given enough time (and nothing else to do!). Plus there's always the chance of loyalists breaking in..

There's only one wizard and the sort of folks who can capture wizards can afford a few guards. Watch him at all times and if he moves outside the designated circle poke him with a stick.

All the answers so far seem overly complicated; why not just keep the wizard in a permanent coma? To trap the Wizard you only need to drug him, then medically induce a coma. (Depending on the time period the "medically" part could be fairly sophisticated or just a "heavy bump to the head whilst sedated" :>)

Some drugs manufacturers even claim to have drugs that can suppress dreaming so the chance of the Wizard accidentally dreaming a spell can be reduced.

And if the trap is going to be made even more dastardly, then the wizard could be made to dream, except in his dream world he is a being of non-wizardly powers.

EDIT: Interrogations would be difficult if the Wizard would need to be woken up each time and the risk there is that the Wizard could use that opportunity to escape. But in a world of Wizards (or even advanced aliens walking amongst humans) perhaps another "Wizard" could be found to help? Then through one wizard manipulating the dreams of the other, interrogation could be accomplished.

• He has to be conscious, so he can be interrogated. Also, I doubt that medieval tech could safely and accurately sedate him. :-) – HDE 226868 Mar 24 '15 at 22:59
• Yes, that'd make interrogations a bit more difficult :-) – James Mar 24 '15 at 23:02

Imprisoning him in his own body seems to satisfy all the requirements, and is certainly well within the grasp of those in this situation and time period. They already have him sedated, and can sedate him as needed. All they need to do is cause paralysis below the neck. He can still communicate, eat, etc with assistance.

This doesn't prevent him from committing suicide because while he cannot move himself, he could determine to fall into the earth below and thus suffocate. There may be ways around this but they depend on how exactly his ability works. For instance, being paralyzed and without feeling he may not know enough about the positioning of all his limbs to successfully cause them to pass through matter.

As an alternate to sedating him all the time, use the sedative as a spinal block which would temporarily cause reversible paralysis during interrogation sessions, and otherwise keep him sedated. This gives him hope of eventual escape, giving him less reason to attempt suicide.

In a space station, or cage suspended in a chasm. Being magical, the suspension can be without ropes or anything to climb up. Can he fly too?

Finding out the exact blend of talents is critical to keeping him imprisoned. If he held back some minor talent, he might be able to puzzle his way out. The captor will assume the most useful escape-relevant talents, so the wiz would come upmwith something esoteric to hold back.

• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:04

Here's an idea I got from playing tower defense games:

Build for your wizard a small cottage in the center of a totally flat, large square field. At each of the four corners, build a guard tower. These towers will have braziers that can be lit at night to illuminate the entire field. Each tower will be manned by some of the best crossbow snipers in the kingdom, working in shifts. The bowmen are given orders to shoot your wizard should he stray a certain distance from his hut.

You can then put the mage to work. He must dig and build a well for water and construct a privy. Provide him with materials to plant and maintain a garden. Perhaps building something will give this villain some measure of dignity and contribute to his rehabilitation?

At any rate, he will soon be self-sufficient and no burden on your medieval society. He will also be utterly unable to escape because he is being watched 24 hours a day. Anyone wishing to visit or interrogate him (with the king's approval of course) can do so easily.

• If he can walk through solid surfaces, he may be able to allow solids (i.e. arrows) to pass harmlessly through his body. Plus, if he has access to a private room (i.e. his privy), then at night he could go into the room, then submerge himself in the ground until only his nose is exposed for breathing and "backstroke" his way across the field. It's going to be hard to see a nose along the ground at night lit only by firelight. – Johnny Mar 25 '15 at 18:58
• If they anticipated your suggested clever escape attempt, the army might also station trained dogs or other animals in the field. Their hyper-sensitive perception of sound and scent would be invaluable. The animals could be trained to alert the guards if the wizard (or his nose) attempted to cross the field. – DrAsimov Aug 4 '15 at 3:03

He can pass through walls, but he will need to walk in order to do so. Suspend him into a anti-gravity bubble, so that he cannot walk and reach any walls, making his special ability useless.

• How could a medieval civilization do this? – HDE 226868 Mar 24 '15 at 20:10
• Suppose that in that univers, something that cause antigravity exists. – Vincent Mar 26 '15 at 4:52

Put him an ordinary medieval gibbet (suspended off the floor, just like every other ordinary medieval gibbet). Station two archers nearby.

Tell him if he leaves the gibbet, he's a pincushion

It doesn't matter that he can step out at will if you make it so that he really doesn't want to.

Simple- three guardsman with knives on his throat with round the clock guard. If he blinks strangely slash him. You haven't indicated that he has any powers that will stop cold hard steel killing him or that he has mind-control. If he has easy mind-control then how did he get captured at all.

No Dragons and Dragon's wizard could survive that- magic takes time and words.

Then you put him in any old normal cell.

Break him (1984 style).

Demands quite the amount of effort but at least once it's done, you no longer have to worry about him escaping or being rescued etc...

But he is not maimed. In all likelyhood he can still do magic. To keep him out of harms way (from the people he's harmed himself) you "imprison" him in an isolated location with a caretaker (minimum or no security)

The problem with all the fancy prisons is that sooner or later someone (maybe himself) will come up with a way to free him. Then again, maybe the escape is the outcome you're after in the long run.

Another interesting idea I do not believe anyone mentioned. If you blind him, how is he supposed to know what direction to run away in? (I just prefer the blinding to breaking hands and limbs and stuff because it makes him physically okay but entirely dependent on others? Or so the jailors may think?)

If they don't know magic better than he, they cannot be sure whatever they do.

Some drastic measures could stop him, but you never know. So maybe: Trim him a bit. They want to keep him alive, so he needs head. But what he needs hands for? He can laye on cold floor and be periodically fed. What he needs hands for? He can lie on cold floor and be periodically fed. He even does not need arms.

And if he dies from wounds/infection/sores from long laying, its his problem.

But better would be hang him, boil him and quarter him (like they did in history with much less problematic persons)

• I've gotten rid of the transmutation ability. – HDE 226868 Mar 23 '15 at 21:04

You can do what we do today - put the prison in the middle of nowhere. There doesn't even have to be walls or guards.

Let him escape - but, he can't travel forever without dying of thirst or hunger. So if his only food source is at the prison site, he cannot escape (unless he steals some food, but then you ensure he doesn't by feeding him little and under supervision).

We build prisons in the middle of wildernesses - if convicts escape they are quickly found, but if they didn't, they'd die of exposure in most cases unless they returned of their own volition.

Or, if he can't fly - put the prison on top of a tall, sheer, tower that is only accessible via a lift system.

• Without walls or guards, what's to keep him from summoning help? He is a wizard, after all, he may have telekinetic powers or other ways to signal for help from afar. Has there ever been a wilderness prison that needed no guards? Even "unescapable" Alcatraz prision had guards and it's believed that some escapees have survived and reached freedom. – Johnny Mar 25 '15 at 19:03
• @Johnny that's because it wasn't that far from shore. Put him on Easter Island and let him swim to safety. Cut all the trees down first, so he can't make a raft though :) – gbjbaanb Mar 26 '15 at 8:37

Simple: Just tie him with a rope more than 10 meters from the ground. Pass the rope by a sheave, and in the other edge just put a rock with the same weight of the mage.

If him try to pass by the rope or something, the weight change and the rope will fall with him.

If he fall, he will die when touch the ground or passing the ground.

• That would probably end up killing him, no? – Serban Tanasa Mar 24 '15 at 19:00
• @SerbanTanasa If he try to escape, yes.. otherwise no. – Santoja Mar 25 '15 at 15:56

Two more solutions:

Take away the oxygen

The complexity of the prison seems to depend on how far he can go holding his breath. Well, one scenario is you reduce how much breath he can hold. How about lining his prison with fires, not enough to kill him, but enough that his breath isn't oxygen rich. Then you have the added benefit of torturing this hated man.

Spikes, spikes!

Solid walls/underground is no fun, you can't see the man. Give him an iron bar cell in an open field, and fill the ground around with spikes nasty enough that he really doesn't want to be standing on them when he runs out of breath.

## protected by HDE 226868♦Mar 24 '15 at 23:56

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