Wanted: Library-themed creatures

[Chronos]

Starting possibly one session from now, I'm going to be sending my 10th-level party on a dungeon crawl through the catacombs below Candlekeep, as a bridge from their current adventure to one of the Candlekeep Mysteries adventures. So I'm going to need monsters. Now, I could use pretty much any sort of monsters, but this being Candlekeep, I'd prefer if the monsters be library-themed to some degree. Problem is, the only library-themed monster I can think of off the top of my head is the nothic, and due to the party's past history, I don't want to use one of those.

So what else does anyone know of? I have access to the Monster Manual and the third-party Creature Codex from Kobold Press. Plus, of course, any homebrew that's freely available online.

[J-H]

I have a Library section in Castle Dracula (Castlevania) on the DM's Guild. It's actually the area included in the preview, BUT the monster statblocks are not included in the preview.
Here are the two most relevant ones:

Spoiler: Halon Elemental

Show

Halon Elemental
Gargantuan Elemental (20x20)
If someone uses a Fire spell in the Library, a bell rings
in the distance. One round later, a thick mist appears
and surrounds the area where the fire was used;
multiple Halon elementals will be deployed if needed.
The elemental appears as a large grayish-white cloud
filling a 20x20x20 cube.
AC 9
HP: 75
Speed 0 ft.
Str Dex Con Int Wis Cha
15(+3) 8(-1) 20(+5) 2(-4) 6(-2) 6(-2)
Saves: Con +7
Damage Resistances Cold, Psychic
Damage Immunities Fire, Poison, non-magical
weapons
Damage Vulnerabilities Thunder
Condition Immunities Exhaustion, Grappled,
Paralyzed, Petrified, Poisoned, Prone, Restrained,
Unconscious
CR 4
Fire Suppressant Fire spells do only 1/2 damage
within the area of the Halon elemental. Persistent fire
effects of 5 th level and lower are neutralized within the
area of the Halon Elemental. Fire-type enemies take
double damage from its attacks.
Oxygen Denier Anyone living creature that begins its
turn within the Halon elemental's misty body must
make a DC 15 CON save or be Slowed (as the spell),
as they cannot breathe. On a failed save, they cannot
speak until out of the elemental’s space.
Actions
Multiattack. The Halon Elemental attacks with up to
6 misty tentacles per turn, with a maximum of two
tentacles per target.
Misty Tentacle. Melee weapon attack, +5 to hit, 10'
range, 1d6+2 bludgeoning damage. If hit, the target
must succeed on an opposed Athletics check (Halon
Elemental rolls d20+3) or be knocked back 10' away
from the elemental.
Tactics:
No more than two tentacles per target per round. The
elemental will attempt to spread its attacks equally
between all creatures within range, regardless of what
faction they are associated with. The party may use
this as a weapon against enemies.

Spoiler: Spell Book

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Spell Book
Tiny Construct
A book launches itself off of one of the bookshelves,
flapping its cover like a bird’s wings. Somehow, it
stays aloft.
AC 14
HP 18
Speed 40 ft. fly (hover)
Str Dex Con Int Wis Cha
1(-4) 14(+2) 10(0) 14(+2) 10(0) 8(-1)
Skills Perception +2
Damage Immunities Psychic, Poison
Condition Immunities Charm, exhaustion, poisoned,
prone, unconscious
Senses Darkvision 120’, Passive Perception 12
CR 1
Actions
Spell Attack. The Spell Book attacks with a spell
once per turn. Its spell save DC is 12, and its Spell
Attack Roll is +4.
Roll randomly each turn to see what magic their
pages will spit out. They will not maintain
Concentration on Hold Person.
1 Hold Person
2 Melf’s Acid Arrow
3 Blindness/Deafness
4 Ray of Enfeeblement
5 Magic Missile
6 Chromatic Orb (not fire)
7 Ray of Sickness
8 Eldritch Blast (2 1d10 rays, same target)
Tactics:
Spell books typically use random targeting for their
random spells. Consider pre-rolling a large array of
D8s to speed up combat when using them.
A Spell book reduced to 4hp or less will disengage
and run away on its turn.

A few other suggestions:
-Invisible stalkers
-Animated Armors (buffed)
-"Museum" type rooms with skeletons from obscure or big animals. What's scarier? An illithid skeleton or a purple worm skeleton? My party was more worried about the illithid skeleton.

[Amnestic]

The peace blossom is a flower cultivated by clerics originally to ensure sanctity inside their places of worship. Since then it has found adoption in other locations such as libraries, personal studies of nobility, and other places of quiet contemplation. Its appearance is notable in that it appears similar to a sunflower, however the centre of the bloom always bears the symbol of a a stylised face with an 'x' in place of its mouth.

Spoiler: Peace Blossom

Show

Medium plant , unaligned
Armor Class 5
Hit Points 19 (3d8)
Speed 0 ft.
STR1 (-5) DEX1 (-5) CON14 (+2)
INT1 (-5) WIS3 (-4) CHA1 (-5)
Condition Immunities Blinded, Deafened, Frightened
Senses Tremorsense 30', blind beyond this radius, Passive Perception 6
Languages --
Challenge 0 (10 XP)
Proficiency Bonus +2
---
Reactions

Wave of Peace. When a peace blossom senses another creature with its tremorsense it emits an aura of silencing magic in a 30' radius. No sound can be created within or pass through the area. Any creature or object entirely inside the area is immune to thunder damage, and creatures are deafened while entirely inside it. Casting a Spell that includes a verbal component is impossible there. In addition, if a creature wishes to take an aggressive action such as casting a spell on another creature or make an attack, the creature must succeed on a DC12 Wisdom saving throw. If they fail this save, they lose the attack or spell, including the spell slot if one was used.

Built off of the Shrieker, but instead of making noise they create silence and (attempt to) prevent hostile actions. They won't be the main part of any encounter instead serving as a pseudo-environmental hazard.

[Man_Over_Game]

You could have ghosts that are being summoned from their stories. The ghosts are very difficult to kill, but they vanish immediately once their story from that book is destroyed (fire, ripping it out, etc).

Perhaps some of the books have examples of ritual circles for research...that unfortunately are a bit too accurate. When a creature dies nearby, larger versions of the same ritual circle begin appearing around the fallen. Unless the book is destroyed in a short amount of time, demons or aberrations are summoned through the circle to wreck havoc.

Homunculi in the library are doing research for their master. They're perfectly content ignoring anything that happens around them, but they are armed with some of their master's powerful spells in case they are bothered or threatened. They aren't very competent and are fairly greedy when it comes to their time, so they will gladly help you in exchange for making their studies easier for them, but will definitely cheat out of doing more work if possible.

Brain mites are tiny little bugs that live underneath the library, hoping to consume any book that touches the floor. They are able to devour the latent psychic energy that people pass onto the paper, and become more and more intelligent the more they spread. They can even cast some spells in a large-enough horde. They fight by shaping the combat horde into an image, similar to how you'd imagine nanobots to function, shaping into things like a fist holding a dagger or into manacles wrapped your legs. They are unable to eat anything but paper, which is why they use other known examples to do harm. The bookshelves and furniture are spelled for protection against them, but there is a harsh penalty for setting a book on the ground.

[RogueJK]

The Candlekeep Mysteries book contains a few library-themed monsters, like the Swarm of Animated Books and the Animated Chained Library.

Mimics, of course, would easily find a home in a library.

[1Pirate]

No Mordenkainen's Tome of Foes? Damn, an Allip would be perfect. The statblock might be knocking around the web somewhere.

[Chronos]

Quoth RogueJK:

The Candlekeep Mysteries book contains a few library-themed monsters, like the Swarm of Animated Books and the Animated Chained Library.

Ah, yes. I haven't looked through the book in much detail yet, and the one monster statblock I saw was for a really stupid monster (the skitterwidget). But of course there are others.

And amazingly, I don't think that my group, in all of their travels, has actually dealt with a mimic. I'm sure I can find a few good places to stick one of those.

[Pex]

Go with puns.

You can have the bookworm, like a Carrion Crawler or Purple Worm
You can also have the bookwyrm, a Dragon

Go Doctor Who with the Vashta Nerata, Shadows

Go Ghost Busters with their librarian ghost, a Banshee
'
Of course there's always the Mimic disguised as a book shelf or a book.

[Thunderous Mojo]

There could be a library of life trapping....a section of shelving, or even a single book that acts like a Mirror of Life Trapping...only the creature is trapped in a book and their life story, (including all of their secrets), is detailed on the page.

I'm forgetting the author's name, and the fantasy series name...but I remember a book series having a very clever idea that how one shelved books, could result in releases of magical energy. Indeed the Dewey Decimal System was derived to prevent this very sort of release from happening, (and also explained why ancient libraries burned down so often...they didn't know how to control the power of books).

A puzzle style trap, that required the group to organize a section of books in a particular fashion in order to pass..seems appropriate.

Even better if Mage Hand or TK is required.

Pex's Bookwyrm is a fantastic idea...as is a Ghostly Librarian...a super charged Banshee...that appears and Wails...whenever noise draws it's attention.

A Banshee that uses Hit and Run tactics and can Wail at least once each time it appears, (and not just once a day or so), will make the party sit up and take notice...and reach for Death Ward.

[Amnestic]

You can also have the bookwyrm, a Dragon

"Let reading dragons lie."

Spoiler

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(Art from the hearthstone card, Book Wyrm)

[Segev]

Animated objects can be books or bookshelves. Mimics can hide as just about anything.

[Guy Lombard-O]

Go with puns.

You can have the bookworm, like a Carrion Crawler or Purple Worm
You can also have the bookwyrm, a Dragon.

Welcome to Xanth!

[Azuresun]

Conan the Librarian, obviously. Or an awakened orang-utan.

More seriously, a sphinx might guard a repository of knowledge.

[Kane0]

Dust mephits, if its a particularly big and old library

[Seclora]

Inspired by accounts from the host of Nightvale Public Radio, Here's an unfathomable horror from the stacks. They've been known to abduct people through the realm of dreams because they have overdue books, are highly dangerous, and known to swarm. I have absolutely no idea what size they are, or what they are, and there is no corroborated account of their appearance save their scream and their long, black, claws. I use them in my setting as the reason nobody collects books, for fear of crossing the threshold over which a collection becomes a library and inadvertently unleashing Librarians into the world.
For an added threat, consider the Flesh Eating, Reading Bacterium.

Librarian
Type, Aberration? / Fey?
CR 5[1.800xp] Prof +3
107 HP(15d8+45)
AC 16[Natural armor]
Speed 40ft
Str 18[+4] Dex 14[+2] Con16[+3]
Int19[+4] Wis14[+2] Cha11[0]
Saves: Int +7, Str +6
Resistances: Lightning, Cold, Psychic
Vulnerabilities: Fire, Thunder
Skills: Perception +5, Deception +6, Arcana +7, Nature +7, Religion +7, History +7, Stealth +8
Senses: Passive Perception 15, Blindsight 60ft

Librarians have eyes, maybe?: There is a 50% chance that any effect requiring a specific sense fails.

Attacks:
Multiattack, make three claw attacks.
Claw: +7/2d8+4

Screech:[recharge 5-6] 60ft radius, 2d8+4 psychic damage and restrained for 1 round. DC 15 Wisdom save to halve the damage and ignore the restrained condition.

[LudicSavant]

Highly effective non-water-based fire suppression systems. These can cause complications in places where the dungeon's lighting has faltered, since it won't tolerate any open flames or the like.

Mordenkainen's Magnificent Mansion-style attendants and amenities.

In Final Fantasy XIV, there are multiple dungeon adventures set in the Great Gubal Library, and they involve a veritable bestiary of unique library-themed monsters, with their own background lore. Good place to look for inspiration.
https://www.youtube.com/watch?v=c_Ehpdcd5kM (First dungeon)
https://www.youtube.com/watch?v=y2wp0wfMnXY&t=6s (Second dungeon, it's called "hard mode" but it's actually a totally separate adventure with new monsters and such)

The Jasidin Wizard that's also my profile picture made a giant library/museum demiplane, and it's administered by a sphinx she contracted (helped out in an adventure like 10+ levels earlier in the campaign), and clay golems that look like murals brought to life (rather like so):

She also summons these when she uses Summon Construct

[Chronos]

Quoth Azuresun:

Conan the Librarian, obviously. Or an awakened orang-utan.

There is, of course, a perfectly good reason why neither of these occurred to me. And as soon as I figure out what it is, I'll get back to you.

Quoth Ludic Savant:

Highly effective non-water-based fire suppression systems. These can cause complications in places where the dungeon's lighting has faltered, since it won't tolerate any open flames or the like.

This is actually canon. The reason for Candlekeep's name is that any flame larger than a candle is instantly extinguished. But alas, the party's first choice for illumination is the cantrip, and it's hard to justify an instance where a Light spell won't work, but the magical fire suppression system still does.

[jjordan]

Variant nothic that is a thaumovore. Covets magic items and will follow the party attempting to steal and consume any magic items they have.

Labyrinth. Shelves are moving or are being moved or the catacombs are simply a maze that has to be navigated. You can elaborate on this and create the possibility that players enter a domain of dread and will somehow need to escape.

Renegade researchers or book thieves. Don't want to get caught and will hide, if seen they may attempt to eliminate the witnesses.

Book curses. Marginalia that come to life. Curses that afflict people who open books or take them. Blindness, itching, summoning a minor demon to torment the book thief, etc...

Allips, simple ghosts, and mimics have already been mentioned. I like animated decorations that protect rooms or books.

Some books may be dangerous to handle because they have become infested with mites (swarm of insects) or the pigments used to color them may be poisonous or have become poisonous.

Intellect devourers recast as books that want to consume the reader. The reader loses a skill or intelligence or simple hit points and has to make some sort of save in order to put the book down.

Dusts and molds in unused areas that can cause simple poisoning or longer term debilitation.

Paper blights. Hide as books but come out as origami creatures and attack sleepers.

[Kuulvheysoon]

Grab some language-related Living Spells.

Take a Living Cloudkill, make it do force damage instead of poison with it's pseudopod, and link it to power word stun with it's Spell Mimicry trait.

Boom.

EDIT: +1 vote for the awakened orangutan.

Spoiler: Living Spell stat block

Show

(Don't worry, that's a 100% legal book preview)

[Chronos]

Quoth jjordan:

Renegade researchers or book thieves. Don't want to get caught and will hide, if seen they may attempt to eliminate the witnesses.

This is the reason they're venturing into the catacombs to begin with. The librarians want the party to go after them because they're book thieves; the party will want to go after them for more personal reasons. But I want to make the process of getting to them interesting.

[Chronos]

So, I looked through Candlekeep Mysteries, and in addition to the Swarm of Animated Books and the Animated Chained Library, there's also a thing called a Gingwatzim that looks like it'd be useful: Basically, a smaller variant on a mimic, that's likely to disguise itself as a book.

From the Creature Codex, there's the Arcanaphage, a weird thing that eats magic; the Bookkeeper, an ink creature that's bound to a book; the Paper Golem, a tiny golem that can poison with ink, as well as a swarm of the same; the Inkling, another ink creature that's born from a spellbook and can cast a few spells; and the Ink Guardian ooze, that's basically an ooze that doesn't harm things made out of paper or wood.

One catch is that most of these monsters (the Creature Codex ones and the ones others have mentioned) are low CR, so I'm going to have to figure out good combinations of multiple monsters to make encounters out of.

A gynosphinx can stand alone. Of course, the classic sphinx encounter is that you must solve her riddle to pass, or else she'll attack you. I'm thinking for a twist on this, I might make the riddle a tribute to the copy protection on old computer games: "The first word on page 72, volume 3 of the manual starts with a G. What is the word? Be warned that, should you leave this room, when you return my riddle shall have changed.". They'd then have to go back through the library, looking for the various "Volumes of the Manual". This would then force them to interact with various other dangerous elements. Or, of course, they could just fight the sphinx, but I suspect my group will opt against that.

[BigRedJedi]

A Medusa librarian, the snakes on her head don't hiss, they shush... and if you make too much noise, she silences you, permanently, and adds you to the library's impressive collection of statuary.

[Rynjin]

Pathfinder has a pretty good one that shouldn't be too hard to adapt. Gishvit. They're not tough, and can even be friendly, if a bit pushy.

Guardian Scrolls are also pretty cool.

[Joe the Rat]

Boggles would be a nightmare with all of the tables and gaps on shelves they can use for their rift tricks. The trick is making them on theme. Tempted to just call them "Borrowers," and have them randomly move books around, or leave them in odd piles.

Borrowing from a player (who I believe borrowed from another source), the lack of a single coherent cataloging system can make finding anything as much a mental maze a a physical one. Minotaur Archivists are highly sought after - both for their ability to navigate the systems and winding stacks of the Deep Collections, but also make effective guardians of said archives. (There's probably a good labrys pun to go with the traditional double-bit axe, but I opted for the significantly more book-friendly Maul.)

Arcanoloths make good patrons for a library. So to speak.

I'd toss in something book-binder themed. for a lower party, I'd suggest a redcap that kills creatures to make parchment, leather, and glue. You could have flesh golems in this role instead (named "Saddle-stitch," "Hardback," and the like).

[Kareeah_Indaga]

…giant dire silverfish maybe? Or a Swarm of same, although someone already mentioned insect swarms.

[KorvinStarmast]

Spoiler: Halon Elemental

Show

Halon Elemental
Gargantuan Elemental (20x20)
If someone uses a Fire spell in the Library, a bell rings
in the distance. One round later, a thick mist appears
and surrounds the area where the fire was used;
multiple Halon elementals will be deployed if needed.
The elemental appears as a large grayish-white cloud
filling a 20x20x20 cube.
AC 9
HP: 75
Speed 0 ft.
Str Dex Con Int Wis Cha
15(+3) 8(-1) 20(+5) 2(-4) 6(-2) 6(-2)
Saves: Con +7
Damage Resistances Cold, Psychic
Damage Immunities Fire, Poison, non-magical
weapons
Damage Vulnerabilities Thunder
Condition Immunities Exhaustion, Grappled,
Paralyzed, Petrified, Poisoned, Prone, Restrained,
Unconscious
CR 4
Fire Suppressant Fire spells do only 1/2 damage
within the area of the Halon elemental. Persistent fire
effects of 5 th level and lower are neutralized within the
area of the Halon Elemental. Fire-type enemies take
double damage from its attacks.
Oxygen Denier Anyone living creature that begins its
turn within the Halon elemental's misty body must
make a DC 15 CON save or be Slowed (as the spell),
as they cannot breathe. On a failed save, they cannot
speak until out of the elemental’s space.
Actions
Multiattack. The Halon Elemental attacks with up to
6 misty tentacles per turn, with a maximum of two
tentacles per target.
Misty Tentacle. Melee weapon attack, +5 to hit, 10'
range, 1d6+2 bludgeoning damage. If hit, the target
must succeed on an opposed Athletics check (Halon
Elemental rolls d20+3) or be knocked back 10' away
from the elemental.
Tactics:
No more than two tentacles per target per round. The
elemental will attempt to spread its attacks equally
between all creatures within range, regardless of what
faction they are associated with. The party may use
this as a weapon against enemies.

I love this. Thanks! Stealing it!

Conan the Librarian, obviously.

*golf clap*

Dust mephits, if its a particularly big and old library

Yes, and I'll add to that.

For the OP: catacombs? Dead things, particularly, incorporeal dead thing.

Wraiths. Specters. Shadows. Banshees. Will O Wisps. Many of them. And, for extra fun goodness, a lich locked away in a coffin that will remain in stasis unless the party are foolish enough to break the seal.
And digging away, deep in the library, is a Volo's NPC GOO/Tomelock Warlock. He's doing some research, and has bypassed the lobby since he doesn't have a library card.

And to whomever suggested the bookshelf mimics: yeah, of course, what was I thinking?

[Chronos]

I really want to use a mimic, but I'm really not sure how. A single CR 2 is no encounter at all, for a 10th-level party, but the nature of mimic encounters doesn't really lend itself to adding other creatures to the encounter.

[Rynjin]

I really want to use a mimic, but I'm really not sure how. A single CR 2 is no encounter at all, for a 10th-level party, but the nature of mimic encounters doesn't really lend itself to adding other creatures to the encounter.

Go with the old standby: Mimics with class levels.

In the Carrion Crown Adventure Path, there is a room with several Mimics with Rogue levels, disguised as coffins. The party basically ends up playing a deadly game of Deal or No Deal as they try to figure out which coffins hold the bodies of vampires they misted earlier in the day.

[jjordan]

I really want to use a mimic, but I'm really not sure how. A single CR 2 is no encounter at all, for a 10th-level party, but the nature of mimic encounters doesn't really lend itself to adding other creatures to the encounter.

Use the mimic to create tension? It's hunting, disguised as an entire shelf of books, sees the party coming and recognizes that it can't fight them so it pulls back into a hiding space beneath the floor to avoid the party. The party sees this. There's no encounter but now the party is wondering if everything they touch might be a mimic.

Use the mimic to reveal a clue you don't want the party to miss? The mimic grapples a party member and drags them back into its lair. The party defeats the mimic pretty easily but finds a vital piece of information among the remains within.

Make the mimic a security system? It's a bookshelf holding the books belonging to a faction; they are hiding their works in plain sight and the mimic won't release the books unless it is fed and will attack those that try to steal the books. Or it could be hiding an entrance to a secret room.

Dire mimic? Just buff it up a little and make it a large mimic that's taken the shape of an entire row or small room of shelves. Double the hit points, give it two or three attacks with the pseudopods, and increase the bite damage. It's still not a huge challenge but it's not a simple fight.

Is it an intelligent mimic? If it can converse it might have all sorts of useful information. Who has been in this area of the library recently. Where a specific book can be found. It might exchange that information in return for favors. Food. Revenge on one of the librarians it considers a threat. A promise to find a book that was never returned to its 'shelf'.

[Joe the Rat]

I really want to use a mimic, but I'm really not sure how. A single CR 2 is no encounter at all, for a 10th-level party, but the nature of mimic encounters doesn't really lend itself to adding other creatures to the encounter.

To borrow a page from K6BD, an entire stack of mimics. A whole collection of Gingwatzim coming off the shelves to swarm the players would be a decent (if mild) encounter.
You might need to use the massed attackers rules (DMG) or build a swarm statblock to make it more manageable.