This magical library is old as the history of magic itself, storing scrolls and tomes of all spells ever devised by powerful wizards and apprentice mages alike. The scrolls are ready to be activated at once, and may be used as a trap. They cannot, however, be activated by the library itself at a whim.

However, this ancient library has no external sensor. It is able to detect presence within its rooms, but has no knowledge beyond if the presence is magical or not (to differentiate between animal and human, mage or just commoner with no magic). The shelves and all parts of the library are its body, but cannot be moved. It knows and feels 'pain' if any part is destroyed. Scrolls and tomes are not included in its body, though.

This library is at a secret location in a desert. Anyone can come in to learn spells within, and many an adventurer has done so, including a few commoners who accidentally stumbled upon it while wandering in the desert. Anyone will have no memory of the library once they leave, but the knowledge and items gained therein will remain with them. Because of this, the place has become a vague legend.

A band of raiders now is trying to raid the library, in hope of gaining the rare and forbidden spells contained within it. These raiders consist of thieves, mercenaries, and mages; as many as 10 people.

How could this sentient library defend itself against these raiders?

Additional background:

  1. Anyone can learn magic as long as they are capable of understanding the working of the spell.
  2. Anyone has affinity to magic just as like smart people understand physics or chemistry.
  3. No mana needed to activate a spell.
  4. Summoned creatures are both 'permanent' and 'borrowed' from other dimension, including Necromancy.
  5. Scrolls can be activated without knowing the innerworking of the spell.
  6. The library is sentient and intelligent, and can communicate telepathically (one-directional via concepts and images, not your daily usual conversation)
  7. This library has benevolent nature.
  8. This is the first time someone send a coordinated raid against the library.

all spells that are documented and presented within the library. If a necromancer creates a new forbidden spell, and no one knows about it, how it works, and no one brings the knowledge to the library, then it is not archived within the library.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Mar 19 '17 at 4:36

19 Answers 19


It sounds to me like the only proper faculties your library has are the following:

  1. Sensation - it can feel it's own body; corollary, it can feel pain if it's body is harmed; additionally, it can detect the presence of any interloper, though it has no mechanism for identifying them specifically, it can gauge an entity's general level of magicallity.
  2. Sentience - it can think, furthermore, it has had a great deal of time to do so.
  3. Communication - it can relate to other minds by projection of thoughts via the medium of images and sensations.

Your library has rather limited options for self defense. It cannot cast spells, as it has no mechanism to learn them (the last man on earth has all the time in the world to read, but broke his glasses?). It cannot manipulate its own structure (thereby trapping, discombobulating, or otherwise interfering with an interloper). It cannot even properly track cause-and-effect, as it has no mechanism for linking any sort of pain it feels to the presence of a particular outsider. In your example, say there are 10 people in a room, and the library experiences the pain of a bookshelf being broken. Did one of the interlopers cause this pain? If so, which one? How would it discover this? It couldn't even ask, because its telepathy only allows the projection (and not the receiving) of thoughts.

Your library needs guardians. Of course, according to your proposed caveats, the library has no means of creating these guardians itself; the most likely explanation to my thinking is that the library has requested such patronage from among its visitors. Perhaps an order of magical monks or bookish scholars now maintains permanent residence therein, or perhaps a single powerful magician calls the library home. Another possibility is that a number of individuals maintain regular custodianship of the library. A select number of wizards, for instance, might take shifts dropping in to place and restore wards, maintenance automagical guardians and servitors, mend books, clean, etc. Such guardianship would not be hard to establish, the library would simply need to communicate to a trusted visitor (perhaps recognized by his magical signature) that it required such guardianship.

A final possibility - the library is telepathic - is telepathy common in your world? Can the magically skilled learn it easily, or at all? If not, it could be extremely disconcerting to even powerful magicians to have their minds invaded, and they would likely have little defense against it. If the library could overwhelm a person's mind with sufficiently strong and malicious communication, it could - perhaps - render them catatonic, overwhelm them with intense fear or anxiety, induce any number of debilitating conditions of the psyche, or even lead them astray and into dangerous encounters.

  • $\begingroup$ At last! Yeah, the original requirements are very restricting, and most answers 'break' a rule, or two. I didn't even mention that telepathy used is one-directional! $\endgroup$ – Vylix Mar 17 '17 at 3:39
  • $\begingroup$ Thanks. Luckily, the one-directional nature of the telepathy doesn't break too many of these suggestions; just the one about the library being able to figure out if a person is trustworthy by having an empathic chat with them, and then revealing the secrets of its automated defenses. $\endgroup$ – CelestialCaveBear Mar 17 '17 at 3:42
  • $\begingroup$ Telepathy is uncommon and have many forms, but at least even apprentice know it exists and receive at least once in the academy. That's why there is spells that protect mind from malevolent projected thoughts. The library was friendly, but distrust grew after an incident involving previous custodians, and subsequent raiding parties leave the library defenseless after disarming most defense mechanism and killing surviving guardians. At last, it become an entity trying to corrupt powerful wizards into giving him corporeal body. Will make a quite good book, no? $\endgroup$ – Vylix Mar 17 '17 at 3:48
  • $\begingroup$ Perhaps! If you update the original question with this new information (specifically, the one-directional nature of its telepathy, and its malevolence and distrust) I'll update my answer to conform to these new restrictions; for posterity. $\endgroup$ – CelestialCaveBear Mar 17 '17 at 3:52
  • $\begingroup$ Updated. And I'm curious how will it respond to raiding for the very first time. After it become corrupted, it's just become your ol' dungeon, after successfully brainwashing one of the raider to become its servant, of course, with minions attacking every visitor. $\endgroup$ – Vylix Mar 17 '17 at 4:14

Since the library can manipulate memory by making people forget itself, I would just use that. Make people forget any plans the library (or whoever set the protection spell) does not approve of before they can get in. Works best with a second defense that makes it difficult to find the library without the memory magic being activated. A magical gate that activates only for people whose minds have been sanitized at a location revealed by the mind magic.

So your thieves would totally forget their plans of plunder before they ever got inside. This could be an active block so that even if the thieves read their own written notes of the plunder plans once inside they won't be able to really comprehend them while inside. The thoughts will simply be erased from their working memory before they can fully process them. Same would apply to all defensive magic that could block the mind magic.

The library could even be little less benevolent and more predatory than you describe. It could add memories of people wanting to bring it new spells. And convince people that they have a deep conviction not remove any originals from the library collection, only copies they themselves have made while in the library.

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    $\begingroup$ +1 for the last paragraph. I like it. However, remember that the library itself cannot feel intention, at least not before they start destroying the wall to search for hidden vaults. I like how the answer is going, however. $\endgroup$ – Vylix Mar 15 '17 at 6:59
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    $\begingroup$ If this was built in as a passive method of making sure the amount of knowledge in the library only ever increased then it would form an interesting plot device. Passively removing memories related to diminishing the library in any way (constantly and without any care as to a person's intention) would leave scholarly types walking out with new copies of things and a vague idea of a wondrous library, while it would leave raiders utterly lost, confused, and likely to starve amongst the books as they try to remember where they are and how to get out. Fun plot point! $\endgroup$ – Joe Bloggs Mar 15 '17 at 7:39
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    $\begingroup$ @JoeBloggs The original idea is just like you said. After they leave with the scrolls and knowledge, as they walked they will slowly wondered how the scrolls come in their bag, and why their understanding on spells is better. People slowly realized there is something in the desert, thus the legend of the library born (it might not state a library, at all). $\endgroup$ – Vylix Mar 15 '17 at 8:37
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    $\begingroup$ I am surprised (nay -astonished!) that no one has yet mentioned Discworld and the Librarian at the Unseen University :-) $\endgroup$ – Mawg says reinstate Monica Mar 15 '17 at 9:32
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    $\begingroup$ @Mawg This is what you're looking for - What you need is an orangutan. – Separatrix 2 hours ago $\endgroup$ – Vylix Mar 15 '17 at 10:18

Why exactly do our bad guys need to raid anything? Surely they're free to go in, learn and/or copy whatever they will and head off with their knowledge intact?

Regardless, it seems likely that their goal would be to steal physical items. Maybe they're lazy and don't want to put in the work to actually learn or copy their spells or maybe there's also physical artifacts of power in the library too.

So how do we prevent that? Well magic obviously, but what kind?.

No Library card, no borrowing!

One suggestion would be warding magics on the exit that prevent you from removing physical items that belong to the library, be they books, scrolls or something else. You try to walk out the door with my priceless tome? It simply disappears from your bag and is magically returned to the appropriate shelf position, ready for the next sage / mage / random commoner to peruse.

This could also double as a maintenance / shelf stacking task so that the library doesn't need any physical servants to go around tidying up after people who are too lazy to put their books back where they found them. The book has been sitting on a desk for an hour? It automatically magics it's way back to the appropriate shelf.

The best part of this is that the memory manipulation makes it super mysterious. Raiders go in, pack their bags and walk out with a dozen priceless books then they get outside and they just don't have them. This leaves them wondering whether they ever actually tried to steal them in the first place because they don't remember their time in the library. Nobody can even work out why the place is impossible to loot!

Plus it's a handy plot hook when someone works out how the wards work and tries to break them?

Physical defense?

Magically returning books are great and all, but that doesn't stop someone having a tantrum and breaking things in the library, causing it pain and suffering and requiring repairs.

The Library needs some sort of physical guardian to prevent this. Magically animated golems seem like a good option. These could be completely autonomous so that the library doesn't need to consciously control them, rather like an immune system. They tidy up, repair damage, do maintenance and deal with pesky viruses (or raiders) all without the library needing to have any input.

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    $\begingroup$ If you can enlist the help of an otherworldly owl then you've got an even better guardian. $\endgroup$ – Joe Bloggs Mar 15 '17 at 8:51
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    $\begingroup$ Or predatory plants whose flowers mimic rare texts (Dantalian no Shoka) $\endgroup$ – Kys Mar 15 '17 at 19:04
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    $\begingroup$ The image that comes to mind is books flying off the shelves and pummeling the miscreants, but they're probably too valuable to use as weapons. But what about bricks disguised as books? $\endgroup$ – Shawn V. Wilson Mar 15 '17 at 20:26
  • $\begingroup$ Just animate the shelves. Start wrecking stuff? The doors on the front of all the shelves snap shut to protect the contents, and they close up and squish you like a bug. $\endgroup$ – Perkins Mar 16 '17 at 0:51
  • $\begingroup$ I wonder what will happen with overdue fees... $\endgroup$ – 1089 Jun 21 '17 at 20:48

Actually, who cares about defending anything?

Nothing in the question says that the library can't have "regenerative" properties. It's already somewhat alive, so it can probably completely "heal" itself, replacing missing scrolls with copies and repairing any shelves, walls, ceilings, etc. Since triggered by damage, the "healing" can be done by "spells used as a trap", so it's involuntary (like in humans) and doesn't need any conscious act from anyone sentient. The library could be built with a healing factor so great that it could regenerate itself from a single sliver of its shelves (no mana is needed, helpers can be temporarily summoned, so really, are there any limits?)

In this case, it probably will welcome raiders, not stop them, so any garbage from breaking things will stick to their clothes, and then will get carried away by the raiders. And then new clones of the library will grow in other places all over the world, spreading the knowledge. Thus fullfilling the purpose of the library better.

  • $\begingroup$ I'm impressed by the last paragraph. I haven't thought about "healing" or "restoration" magic, so this come as a surprise to me. The last paragraph is a good plot idea, though this is not exactly what I'm looking for. Thanks! $\endgroup$ – Vylix Mar 15 '17 at 8:44
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    $\begingroup$ Of course, if those other libraries themselves are regenerative, you may end up with a situation where the libraries turn into invasive pests, with people constantly having to eradicate satellite libraries as they start growing in farm fields, crowded cities, busy sea routes, etc. $\endgroup$ – JAB Mar 15 '17 at 15:51
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    $\begingroup$ A variation could be that there aren't really any physical scrolls, just magic the library itself has to present the image of such scrolls. When a raider "takes" a scroll outside the library, the magic is dispelled, and the raider has a handful of nothing. A scholar who brings blank scrolls and ink into the library, and makes a copy of the image (possibly by casting another spell) can take his copy out just fine. $\endgroup$ – Monty Harder Mar 15 '17 at 18:24
  • $\begingroup$ +1 for creativity! Though I was a bit wary as it did not answer the OP's question directly... $\endgroup$ – LiveMynd Mar 16 '17 at 4:30
  • $\begingroup$ You might as well ask this the next time you are suffering from a headcold. $\endgroup$ – can-ned_food Mar 16 '17 at 6:56

I own a beautiful rare book on fireworks. It should be titled "Explosives for Idiots, a Guide to Extraordinary Displays of Self Harm." Recipes include "Not smoke, but Brain Destroying Mercury Vapor", "Really Real Blinding Heat", "Intensely Vibration Sensitive Explosives", "Super Sticky Sweat Triggered Igniters that Produce Poison Gas" and "Put All That Stuff in a Rocket, What Could Go Wrong?"

I paraphrase. I am trained as a chemist, and would recommend the book but for the spectacular deaths and injuries doing so might cause some idiot somewhere. A library filled with similar "magic" tomes would not need much defending.

  • $\begingroup$ Interesting take on the question. Welcome to WorldBuilding.SE! If you got questions about the site please take the tour and visit the help center. The Meta Site is also a good place to learn about the Site. Have fun! $\endgroup$ – Sec SE - clear Monica's name Mar 15 '17 at 19:33
  • $\begingroup$ I may have to compile my stacks of notes into a book with that title just for the humour value.... $\endgroup$ – Perkins Mar 16 '17 at 0:54
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    $\begingroup$ @AdiNugroho: Or stick them in the entranceway. The sensible readers will know to leave all enough alone, the raiders will try to smash and grab, only to have their faces eaten off by The Dread Tome of Jimmy. $\endgroup$ – Joe Bloggs Mar 16 '17 at 7:39
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    $\begingroup$ The problem here is if the raiders simply want to steal scrolls, not to use them, but to sell them on the black market. As long as they don't try to activate any spells they would be safe (if I read the question right). $\endgroup$ – DLosc Mar 17 '17 at 7:11
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    $\begingroup$ Your answer is the only mention Google can find of such a book. Maybe you're the first one to read it and survive long enough to put it on the internet? $\endgroup$ – Francesco Dondi Mar 17 '17 at 11:17

The library is guarded by a great and terrible monster, a dragon with tough, leathery hide like book bindings. Its wings are scrawled all over with chaotic markings in the shape of letters from every known script. Its teeth are thin as sheets of paper, but stronger than steel. Its presence is truly fearsome, as it projects a magical aura causing all around to fall silent.

It is ordinarily a docile, harmless beast, but woe betide any who causes harm or offense to the library, for the Bookwyrm will hunt them down!

  • $\begingroup$ Its teeth are thin as sheets of paper: I present you Paper Cut $\endgroup$ – Vylix Mar 16 '17 at 1:46
  • $\begingroup$ Given that summoned creatures are allowed, the library staff are likely to consist of something pretty fierce and pretty resentful at its eternal binding to service. Destroying interlopers is likely to be one of their few pleasures and there's no reason why a demon, angel or whatever can't sense intention or draw reasonable conclusions about such. $\endgroup$ – bp. Mar 16 '17 at 8:58
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    $\begingroup$ You did this just for the pun didn't you. $\endgroup$ – Michael Mar 16 '17 at 17:36
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    $\begingroup$ @Michael *innocent whistle* $\endgroup$ – Mason Wheeler Mar 16 '17 at 17:39

Is the library "anyone"? If so, it can learn spells. A lot of spells.

Do not mess with a sentient library.

Especially, do not mess with a sentient library that has a sense of humor.

On the most basic level:

Dispel magic until there is no more magic detected and then Baleful Polymorph bad actors into bats or something else that eats moths.

If you want to be kind, give the bats unique markings and then list them in a log book. That way the librarians can question them and, maybe, end their sentence.

If polymorph doesn't work, disintegrate after disintegrate will solve the problem. I few gust of winds will clean that man right out of my stacks.

  • $\begingroup$ Oooh... I like this! Although the library cannot cast spells (it definitely can learn how to, though), it is definitely an interesting approach to dealing with them. I like the log book part! $\endgroup$ – Vylix Mar 17 '17 at 3:06
  • $\begingroup$ Perhaps a minion could do the spell-casting for it. The telepathy is one-way, so the library could tell the minion what to do; it wouldn't even have to be intelligent if it could work as a telepathy-controlled puppet. $\endgroup$ – wizzwizz4 Mar 17 '17 at 18:04

A powerful defender.

A library with the attributes you describe would be a natural stronghold for a powerful mage or cleric. Access to all those spells would eliminate the need to travel to find new spells and items. Occasional visitors who conveniently lose all memory of the location once they leave would be a good source of whatever the defender needs. Additionally, an ally like this who has a scrying stone or other means to communicate with the outside would be an invaluable resource to help the library defend itself.

If a symbiotic relationship can be established with a friendly ally, that would be great for the library. On the other hand, if this defender is evil and devotes him/herself to attacking and looting all visitors to the library, that could provide even more plot fodder for the adventuring party seeking the library.

Along the same lines, if this raiding party does contain mages of a scholarly bent, one of those may see the advantage of making the library his home and decide to stay here, perhaps betraying his comrades in the process, to become that defender.

Depending on how deep you want to get into this idea, it's entirely possible the library could become home to a school of magic, as well. The synergies involved in this would be similar to the other options above.

  • $\begingroup$ This is too, become possible approach after I read it several times. Both library and wizard will mutually benefit from protecting each other. Hmm... what if one of them actually using the other? This would be interesting if the library lie to the wizard of 'Eternal Youth' enchantment, or 'Resurrection' when he die... $\endgroup$ – Vylix Mar 17 '17 at 3:26
  • $\begingroup$ The only obstacle I could see is the positioning in the middle of a desert. Food and/or water could be an issue, but, depending on your system of magic, that could be compensated for using magical spells or magical attributes of the library (perhaps providing food and water and other comforts). $\endgroup$ – Adam Miller Mar 17 '17 at 13:31
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    $\begingroup$ @AdiNugroho I don't know if it's interesting to you or not but the anime/manga series D.Gray-man had a facility with a tech/magic combo guardian named Fou (or For), who was essentially part of the building, could not leave its grounds, and existed primarily as a security system. She wasn't a human, more of a "force" that sometimes chose to appear human as a convenience, and could materialize out of walls and such. Maybe that's somehow inspirational. $\endgroup$ – Jason C Mar 17 '17 at 19:30

There is nothing physical to take

There aren't really any physical scrolls, just magic the library itself has to present the image of such scrolls. When a raider "takes" a scroll outside the library, the magic is dispelled, and the raider has a handful of nothing.

In contrast, a scholar would bring blank scrolls and ink into the library. A physical transcription of the scroll image (possibly "automated" by casting another spell) can be removed just fine.

There could also be some magic that automatically reads all spell scrolls brought into the library (analogous to the way that any books found on ships at Alexandria were copied for the Library there). This could cause maintenance problems with duplicates, but a magical "source code repository" system could dedupe the spells, and even track multiple variations of spells with minor differences.



The library could try to ascertain the intentions of newcomers by placing more or less obvious hints pointing to a supposedly "forbidden" section, containing unimaginably valuable and dangerous magics. The library could also emphasize them with telepathic communication.

This could prove useful, as those with malevolent intentions (and an utter lack of common sense, since they're trying to raid a legendary magical library) would much more likely be drawn to items out of their depth.

The actual bait section need not be anything more than an area filled with gibberish books to confound even the brightest of mages, since bright and driven individuals are often given to find patterns where there are none.

Other, fancier, means could involve combinations of direct teleportation out of the library, destruction of magical items, induced insanity, disfigurement etc. Just to give some ideas.

  • $\begingroup$ Baiting can often frustrate and offend the raiders. Will make them want smash more of the library. Doesn't seem a good defence. $\endgroup$ – avek Mar 15 '17 at 12:12
  • $\begingroup$ Messing around with the bait could trigger a instant kick from the library though since the library knows the intents after someone started messing around there $\endgroup$ – masterX244 Mar 15 '17 at 12:30
  • $\begingroup$ @avek, you're right about that. The bait either needs to be very convincing (i.e. trash in disguise) or the library would need to deal with the raiders before they can figure out they've been fooled (maybe as per masterX244's quick kick). $\endgroup$ – vodrilus Mar 15 '17 at 12:40
  • $\begingroup$ Direct teleportation out of the library is not included in library's ability, but that can be made possible if someone build the mechanism/set trap, either by his good intention to help/protect the library, or by ill will to thwart next visitors out of the library to eliminate competition. Heh, he didn't know when he left he won't remember a thing about the library, including the traps he set when (if) he come again. Poor soul... $\endgroup$ – Vylix Mar 17 '17 at 2:59
  • $\begingroup$ A promise of a gateway to even greater power might lure raiders to teleport themselves willingly far away out of the library - arriving to a distant location without any recollection about where they came from. Offer raiders a teleportation spell as a first choise. $\endgroup$ – diynevala Aug 31 '17 at 7:35

Use the telepathy as psychological warfare? Implant flashes of thought, ideas, imagination seeds in the minds of the raiders, causing them to turn on each other. Another idea would just be weaponized communication. Loud, bright, otherwise overwhelming sensations blowing someones mind apart whenever they look at a specific door, or in a direction away from where the library wants them to go. The sound could be used to cover up groups calling to each other, etc etc

Theres also the possibility of other people who just happen to be studying there at the time of the attack.


Are you familiar with Discworld's L-space? In that case it is just a side effect of the accumulation of magic, but in your case it can very well be a sentient choice. Navigating the depths of the library can become impossible, even with people taking conventional precautions like making a map or leaving a trail. If what you want to protect from is just looting/taking specific things away, then raiders can be locked in until they give up their loot, or even forever if need be. Or they can be led to some dangerous specimens stored within the library.

And protecting from destruction or "cutting a way out" can be achieved just by having dangerous results from destroying magical items such as books and scrolls.

The walls, floor and shelves need not physically move, and you can still give it unconventional, even varying space (or spacetime) geometry. Or you can achieve that unnavigability by affecting the minds of the people inside it, since you already have it erasing their memories at the exit. Though if you go that route, you might as well make it affect their intentions and actions directly.

[almost off-topic: experience getting lost in L-space first-hand in the Discworld MUD game]

  • $\begingroup$ I'm not familiar with most sci-fi stories, unfortunately. I've never considered creating unconventional room/space-time as an answer, so this add to my possible choice. And dangerous specimen. Of course! Keeping rare beasts in library is feasible too! $\endgroup$ – Vylix Mar 17 '17 at 2:42

We can use three options to make our library from sentient to sentinel. Illusion, destruction, restoration.

First one up is illusion. The library will have a prototype of itself conjured as an illusion. People stumbling upon it will be tested for their intentions here. If they are hooligans or have malevolent intent, the library will be sealed away from them. Otherwise, they will get into the true library seamlessly.

Destruction. There will be a gauntlet leading up to the library. And the library will be full of traps. Any violation of 'rules' will trigger traps. So much for being a benevolent library.

Restoration. At the very sensation of being intruded, the library will cocoon itself into a protective shell, which will be virtually impervious to any magical/physical damage.


One possibility is for the library to have some sort of detection system for knowing whether one's intentions are good or bad (you said it is telepathic and intelligent) and then flood trespassers minds with horrible images and therefor traumatizing him. :)

  • $\begingroup$ By itself, the library has no way to feel the malicious intent of a presence, except when there is damage done, it can guess a group of people in a room has hostile intention. $\endgroup$ – Vylix Mar 15 '17 at 5:24
  • $\begingroup$ +1 I like the idea of defending telepathically. However, the mages can cast 'protection against evil' or 'calm' to protect from such effects. $\endgroup$ – Vylix Mar 15 '17 at 6:40

I would suggest a different tangent. Rather than defending itself, it would instead proactively bribe people with valuable knowledge to recover stuff.

Raiders steal it's books - library then offers an arcane academy access to to make copies of some scrolls that they REALLY REALLY want. But first - they need to go find the raiders, recover the books and ... discourage repeat performances.

Maybe better yet - it 'encourages' them to prevent it in future, because it would be a shame if the arcane lore of a hostile nation advanced a few hundred years overnight, now wouldn't it?

  • $\begingroup$ Yep, this is similar to what I've been originally thinking. But I'm a bit confused about the second paragraph, could you clarify what you mean by 'they need to go find the raiders' ? Do you mean find 'other raiders' ? $\endgroup$ – Vylix Mar 17 '17 at 3:03
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    $\begingroup$ Magic library sends emissary to big_magic. Says: "These guys have stolen my books. That's your problem now. Return them to me and I will give you awesome_spell. You have 3 months. If you don't, I will make the same offer to other_nation who you hate.". Or maybe just play them off against each other directly - here is a challenge, the reward is X. GO. $\endgroup$ – Sobrique Mar 17 '17 at 9:13
  • $\begingroup$ @Sobrique Playing them off against each other may result in the accidental destruction of the artefact, if they're fighting over it. $\endgroup$ – wizzwizz4 Mar 17 '17 at 18:06
  • $\begingroup$ No defensive strategy would be perfect. $\endgroup$ – Sobrique Mar 17 '17 at 18:40
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    $\begingroup$ So this how we get random quests in Fate. Who knows the village just outside the dungeon is part of the sentient dungeon? $\endgroup$ – Vylix Mar 18 '17 at 2:02

What would happen to a primitive man blundering into an electricity sub-station? Especially an avaricious one attracted to shiny copper thingummies?

I wonder whether the library needs to defend itself, given its contents. OK, so the scrolls would also need to be somewhat sentient. But even the most primitive life will defend itself against destruction to the best of its ability, and will interpret an attempt to drag it away from its home as an attack on its life.

I'd expect a hostile visitor to meet his end attempting to read or steal a potent scroll, and discovering too late that the scroll is reading him and stealing his mind as he does so. Indeed, some of the less pleasant scrolls may have this attitude even towards humble students. The library may actually offer advice about the correct degree of mental humility and the shelves where only the most potent of mages should attempt to browse. Or, if it feels threatened, to lie.

  • $\begingroup$ The scrolls are not sentient, and cannot be activated by library. But this is an interesting choice. $\endgroup$ – Vylix Mar 17 '17 at 3:00

From your description, the only possible weapon in the library's arsenal is telepathic communication. It cannot move the shelves or the books, so physically hurling either towards intruders isn't an option. The consciousness of the library is essentially a brain in a jar - something that can feel & think, but not physically interact with the world. And affecting memory only seems to occur upon the person leaving the library, so that's not really an effective weapon while they're still IN the library.

Now, that being said, the telepathic communication alone - even just in the form of images & concepts - can be used to distract & confuse interlopers. While intruders are reading the books and attempting to learn spells, the library can make them see the wrong words, or visualize the wrong images. Thus the very mind of the intruders themselves becomes the weapon.

Perhaps the entire library is under an enchantment - the same enchantment that gives it life - that would make the books turn to ash if they leave the library. It could even be the same enchantment that makes them forget about the library, and that would tie everything together as well as giving the library a defense mechanism external to itself.

Also, if this is for a novel or story, you may want to explain WHY the library needs to defend itself. If the books themselves are not part of its "body", then would it necessarily care if someone takes a book? If so, why? Does it feel possessive of the books? Greedy, even? Otherwise, it would only care if someone were to harm the library itself, the shelves, etc.

  • $\begingroup$ Yes, I know very well the setting is very restricting. Good analogue with 'brain in a jar'. This is for background story of a game I'm making, and based on many great answers here, I already have slight hints of possible plot twists, including 'predatory' like @Ville Niemi suggested. Originally, defending is necessary to protect the world, because of forbidden spells stored within, but I really like how the discussion here! $\endgroup$ – Vylix Mar 17 '17 at 2:49

If you really think it needs to defend itself, it could easily do so.

Using telepathy

By using its telepathy, it can introduce images into the minds of any looters. If the looters don't understand what's going on, it might scare them and even make them go insane. Even if they do understand, it might still work.

Some of the lesser (or everbody even) gifted might be persuaded that the images represent real events; the memory of one of the other members of the group stealing from you or trying to harm you in any way may be just enough to make those suspetible to the suggestion assault those who aren't, forcing the group to dismiss itself.

Using scrolls

Simply activate the kill all people scroll.

  • $\begingroup$ The library cannot activate scroll by itself. If previous visitor set a scroll as a trap, then the scroll can activate by itself, otherwise the library itself cannot set the trap. Based on this, possible explanation might involve the library 'ask' or 'convince' visitors to set traps in a specific sections, where unwanted raiders could be lead into. $\endgroup$ – Vylix Mar 17 '17 at 2:54
  • $\begingroup$ @AdiNugroho hereby striken from the answer. $\endgroup$ – Clearer Mar 20 '17 at 8:01

The library doesn't exist

I've my idea reading the @Monty Harder answer. Instead of only the books been a proyection -so you can't steal them-, all the library is one.
There is an special and ancient spell casted a long time ago in the middle of the desert, the spell is the library itself. When someone reach to that location they are induced into a illusion and they see "the library", but they aren't there really, so you can't destroy it or steal it (you still are able to make a transcription of a book).
Even, if people is making trouble (like attack another people or try to destroy the library), it's able to defend itself making illusions on the people. It can make people see nightmares to scare them, or simply make an illusion when the mercenary archived to destroy the library or steal all the books, and when they get out of the desert, they discover that all was an illusion.

The library is able to rebuild

The library was build with two spells.

  • Reconstruction: This spell self repair the library when it's damaged (turn off fires, reorganise books, rebuild wall, etc).
  • Conservation: This spell desintegrate all the matter (even book) stolen from the library in order to archive the conservation of mass and energy of the reconstruction spell.

The library is in a pocket world

To enter into the library you have to travel across a portal. The library is in a pocket world and was casted with some kind of time loop spell or conservation mass spell that protects it.

  • Time loop: The library is always in a time loop, if you break it, you have only to wait for the end of this iteration in order to loop again, and each time it make a loop, all the library is restored to it initial form. If you stole something, when the library reach to the next loop the stolen things will dissappear (and re-appear in the library).
  • Conservation mass: Inside the pocket dimention there is a conservation of mass, the library can't loss mass. You know how works a teleporter? It save the pattern of the item, turn the into into raw energy (90 petajoules per grame) and rebuild it using the pattern an the energy. Well, the library do something similar, it has an stored pattern, and the pocket world can loss energy or mass, for each grame of stolen thing you have to left a grame, or simply the portal won't work, then, all the matter inside library is turn into energy and rebuild again using the saved patters. The library has just regenerate completely.

The library is in another dimention

This is quite similar to the first title, but instead of been an illusion it is in another dimention, and there is a passive spell in the area to see that dimention.
Because it's another dimention you can't touch them (or steal), so all there aren't books (you can't change of page), there are a lot of pergamines already opened and floating in the walls.


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