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Creature Keeper · Long Island Dungeon Master
Under the oldest inn in Millbrook sits a knot of rats grown together at the tails, and for thirty years its subjects have carried it tribute: every ring and key and coin and letter this town has ever lost. Including the ones a murderer needed lost.
At a glance: four blocks, one court. The King Under the Floor CR 4 · the Stop CR 1 · Tithe-Swarm CR 1/2, field three · the Snuffers CR 1/4. Written for four characters of 5th level, and fielded at levels 4-7 and for parties of three to six by changing how many of these same four creatures come. Mini toolkit: a d20 of what thirty years put under the floor. One location and three ceiling heights. No new condition, no new resource and nothing to keep on a scrap of paper: the crawl runs on movement costs and saving throws, and every one of them is printed.
The Crooked Swan has stood two hundred years and its rats have been carrying smalls down to the dark under the taproom for a generation of landlords who called it bad luck. Nothing down there was ever eaten. Last week the new landlady's terrier came up the cellar stairs with a dead man's locket in her mouth.
1. The court is the product, not the King. The King barely moves. Everything interesting here is what the other three do around it, and all of it runs on rules you already know: movement costs, saving throws, and one short standing order per caste. If you find yourself inventing a subsystem, you have gone past the design.
2. The ceiling is the encounter. One dial, and it is headroom. Standing up, this court is a nuisance you could clear with a broom. Under two feet of joist it is a horror, bought with movement costs rather than a new mechanic. The counters below all work on purpose: a pack whose only answer is a good roll plays once.
3. Nobody down here is evil. The court is animals doing what a court does, and nothing it took was ever eaten, burned, buried or spent. If your table wants a villain to put down, this is the wrong pack. What it gives them is a building that wants them to leave.
Open DM Tools. The d20 of the midden rolls from the table roller, the whole court is pre-loaded in the initiative tracker, and the crawl to the midden is already built as a five-box clock so you can count the rounds it costs to get there.
Rat catchers know the thing the trade does not advertise. Sometimes rats knot. Tails fuse, a dozen bodies drag one shared swollen life around under the boards, and the loose rats feed it and serve it and bring it things.
Bright things, mostly. Small things always.
The Crooked Swan has stood two hundred years at the top of Millbrook's one street, and under its taproom floor is a hollow between the joists and the cellar ceiling where a knot has been sitting since before the current landlady was born. The court brings it tribute. Wedding bands off washstands. A bailiff's seal. Nine years of one man's letters. A christening spoon. And one autumn night thirty years ago, a bloodied cuff and a snapped locket and the signet ring of a man the parish register says drowned upriver, unwitnessed, wearing that ring.
Nothing down there was ever destroyed, because that is not what tribute is for.
Last week the terrier found the locket. Nan Caldwell took the Swan two years ago and brought a small ratting bitch called Sixpence with her, and Sixpence came up the cellar stairs on Tuesday with something gold in her teeth and a great deal of opinion about the floor.
One location, one axis, and the axis is headroom. Draw it once and the encounter runs itself.
the taproom at street level, boards worn thin between the joists. Down the back stair, the cellar: four feet of clearance over a dirt floor, barrels on stillage. Off its north wall, the crawl: dry stone and packed earth under the taproom floor, about two feet high and forty feet long, with a chewed-out alcove one square wide at the mouth and something fat and grey already sitting in it. At the far end, past two chewed corners, the midden and the thing sitting in it.
The taproom (standing room). Nothing here is dangerous. Swarms cross open boards to reach anybody, you have reach, and a lantern on the bar stays there. A party that fights the court on its own terms wins in two rounds and learns nothing.
The cellar (about four feet). Crouched work, and it costs nothing: four feet is enough to stoop in, so a Medium creature moves at full speed, is not prone, is not squeezing, and takes no penalty to anything. What it loses is a polearm, a longbow and any idea of a formation. This is where the party learns what the Snuffers do.
The crawl and the midden (about two feet). This is the whole encounter. Two feet of clearance is under everything with legs, the rules do not make that ruling for you, so the pack makes it here and prints the arithmetic.
Who can be in the crawl at all. A Medium or Small creature can enter, and while it is in there it is prone and squeezing at the same time. A Large creature cannot enter at all. The King is the exception that proves the rule: its hollow is a Large space chewed out around it over thirty years, two feet high and ten feet across, and the King has not stood up in any of those years. A Tiny creature moves in the crawl the way it moves anywhere, upright and at full speed. A swarm using its Swarm trait pays nothing either, because a swarm is not one body and there is nothing about it to squeeze. The Stop, the Tithe-Swarms and the Snuffers all live down here. None of them is prone or squeezing in the crawl, so none of them pays any of the costs below, and all three blocks say so.
What a foot of the crawl costs a person. One foot to move, one more to crawl, one more to squeeze. Three feet of movement for every foot travelled, and four feet inside the two rough squares you marked before the fight. So an ordinary five-foot square of crawl costs 15 feet of movement and a rough one costs 20, and a 30-foot speed buys two ordinary squares in a turn or one rough one, because the 15 feet left over will not pay for a 20-foot square. Walk the eight squares in order and it is six ordinary and then two rough: three turns and then two more, so forty feet of crawl take five rounds instead of two. Dashing does it in three, at the price of doing nothing else. That is the whole clock of this encounter, and it is why the objective is at the far end.
What it costs them to fight. Their attack rolls are at disadvantage: squeezing says so and being prone says so, and that is one disadvantage rather than two, because disadvantage does not stack. Their Dexterity saving throws are at disadvantage, from squeezing. Attacks made against them from within 5 feet have advantage, which in a corridor five feet wide is every attack the court makes. Attacks from further off cancel out: squeezing hands the shooter advantage, prone hands it disadvantage, and the shooter rolls straight. That matters exactly once a fight, when somebody back at the cellar end tries to help.
And they cannot stand up without lifting the floor. A druid who drops out of a Tiny shape halfway down the crawl is simply prone and squeezing where she is.
Do not soften it. Tell them what a foot of crawl costs and what is in the alcove, then let them look down forty feet of dark with a candle and decide. This pack does not need a surprise to work.
None of this is a mechanic. It is just true when the party arrives, and it is what makes this a pack instead of a monster.
There is nothing left to burn. The Snuffers have eaten tallow, wick and lamp oil out of this cellar since before Nan Caldwell was born, and the Swan buys candles by the box and has stopped mentioning it. A party that plans on relighting has nothing to relight with. Say it early, as a landlady's complaint about the price of candles. A party that can cast light is exempt from all of it and is supposed to be.
The routes are theirs. Every crawlway has a bolt-hole at the far end that a rat can use and a person cannot, and the hoard sits behind the longest of them because that is the one spot in two hundred years nothing with hands has ever reached. The thing in the alcove is not hidden: anybody who puts a light down the crawl sees it looking back, and it does not move while they look.
The floor is honeycombed. Mark two patches of difficult terrain in the crawl before you start, one square each, and mark them as the last two squares before the midden so the clock above is the clock you get.
And the town knows. Not about the knot. About the losses. Two generations of Millbrook have been quietly certain the Swan eats small things, and four people would rather the cellar were filled in than opened.
The party comes down expecting vermin. What is down there is an archive with teeth. The moment somebody lifts an object out of the midden, this stops being pest control and becomes a robbery, and the court fights robbery the way any court does. And once the town hears the midden exists, the fire in the Swan's cellar four days later is not an accident.
Initiative, four counts. One for the King, one for the Stop, one for all the Tithe-Swarms together, one for the Snuffers. Four decisions a round, and the court is never waiting on itself. There is no such thing as "the court's turn" and the pack never asks you to pretend there is.
And they are a puzzle, not a trap. Every caste does the same thing every fight, forever, and the lists below are the whole of it.
Four castes, four short lists, and the lines in a list do not overlap: exactly one of them is what that creature does this turn. Read from the top and stop at the first line that fits. That is the whole coordination model: nobody plans, everybody has a job, and the jobs feed each other.
The King. 1. If something has been lifted out of the midden and the King can perceive who is carrying it, that creature is the mark, and the King Gnaws it if it is within reach. 2. Otherwise, if The Scream has recharged and two or more of the court are more than 15 feet away, it screams instead of biting. 3. Otherwise it Gnaws whatever is in reach. 4. Otherwise it does nothing at all, because it does not have to.
The Stop. Its square is not one of its choices. On its first turn it takes the square the party came in by, and after that it does not leave that square for anything, the mark included: a door that chases is not a door. Holding the square costs it no movement and no action, so it still acts every turn. Its action, first line that fits: 1. Anchor Bite whoever is adjacent and carrying something out of the midden. 2. Otherwise Anchor Bite whatever else is adjacent. 3. Otherwise nothing, because a door waits. Its reaction: anything that tries to enter its square gets Nobody Goes Past. And the moment the King dies, it stops being a door and leaves.
Tithe-Swarms. 1. A swarm that is carrying something leaves down the nearest bolt-hole and does not come back. Nothing below applies to it. 2. Otherwise, if its Tithe took nothing last round from the creature whose space it is in, it uses Bites on that creature this round instead. 3. Otherwise, if the mark is somewhere it can reach, move into the mark's space and use Tithe there. This is the chain: the King names, the swarm collects. 4. Otherwise use Tithe on whoever it is already sharing a space with, and if it is sharing with nobody, move toward whoever is nearest the midden.
The Snuffers. 1. Snuff the brightest nonmagical flame it can perceive, and cross the whole crawl to get to it. 2. If there is no flame it can put out, move into the mark's space and use Bites. 3. If there is no mark, share a Tithe-Swarm's space and bite whoever that swarm is working on. They are not there to kill anybody. They are there to make the swarms' job easier.
The chain, in one line. The Snuffers take the light, and a creature that cannot see the swarm in its own space does not get to choose what the swarm takes. The swarms take the objects. The King names whose objects to take and screams the court into position. The Stop makes all of it take longer by standing in the only way out. Break one link and the other three get worse, which is the only honest test of whether a pack is a pack or four monsters in a bag.
And when the King dies, stop reading these. What is left down here is a pack of rats with nobody telling them anything: a swarm holding something goes down the nearest bolt-hole, the Stop leaves its square, and whatever is cornered bites whatever cornered it. And every unburdened creature of the court goes down the nearest bolt-hole as well, swarms and Snuffers alike. Only a cornered one stays to bite.
Magical light. A light cantrip cannot be snuffed, and from the mouth of the crawl it reaches most of forty feet in bright and dim. It shuts the Snuffers out and puts the choice of what gets stolen back in the party's hands. The price is that they still have to crawl, still fight at disadvantage, and have just told everything down there precisely where they are.
Darkvision. Most of the same result: darkness inside the range is only lightly obscured, so they see the swarm sharing their space and they keep the choice. Two prices, both real. Lightly obscured is still disadvantage on every sight-based Wisdom (Perception) check, which is every check anybody makes on a heap of a thousand small objects. And darkvision has no colour in it, so what has dried on a linen cuff is mud until somebody brings a light to it. Sooner or later somebody carries a flame to the midden, and that is the Snuffers' whole fight.
Anything Tiny. A familiar, a Tiny wild shape: full speed down the crawl, no crawling, no squeezing, carrying a pound of somebody else's history back out. A table that thinks of it has earned it. The price is one object a trip, and a familiar has single figures of hit points in a corridor holding three swarms.
Area damage that is not fire. A shatter or a thunderwave kills swarms three at a time and does not burn the archive. Let it feel clever. The price is the corridor: five feet wide, so the spell that catches three swarms is catching whoever is in front of them, and forced movement does nothing to the King.
Moving the Stop. It is an animal, not a fixture. A shove, a grapple or a thunderwave takes it five feet out of the hole it is plugging, and out of the hole it is just a fat rat. The price is that shoving anything in the crawl is done from prone, and the Stop walks back into its square next turn, because that is the whole animal.
And what does not. Killing the swarms first, because they are not the objective and there are more of them. Talking, because the court is animals. Pulling the King out of its hollow, because that is what Grown Into the Boards is for.
Three ways, and all three of them are wins.
d20 · the midden as an archive
Here, pick rather than roll: rows 7, 13 and 18 are the murder and the rest is the town. Anywhere else, roll it and you have a hoard with a history under any old building you like.
| d20 | What thirty years put under the floor |
|---|---|
| 1 | A christening spoon. Silver, worn thin, initials rubbed away. It went missing the winter Nan Caldwell's grandmother kept the Swan, and it was a christening spoon for a christening that was cancelled. Worth 5 gp and an argument. |
| 2 | Forty-one keys on a loop of gut. Nine of them still open something in Millbrook. Nobody alive knows which nine. |
| 3 | A bailiff's bronze seal, cracked across the crest. The bailiff swore he lost it in the river and had a new one struck at his own expense. Two summonses signed with this one are still on file at the moot hall. |
| 4 | An inscribed wedding band that fits nobody. It fits nobody who has ever lived at the Swan, and the inscription is a date eleven years before the inn was built. |
| 5 | Nine years of letters in one hand, unopened. Addressed to a woman who left Millbrook eleven years ago. Somebody was taking them off her doorstep, and the rats were taking them off somebody. |
| 6 | A child's tooth in a twist of paper. The paper has a name and a date on it and nothing else. Both are legible. |
| 7 | A man's linen cuff, torn at the seam. What has dried on it is not river mud. Nobody in Millbrook has worn linen at the cuff for thirty years, which narrows it a great deal more than the party will realise at the time. |
| 8 | A pewter pint measure, shaved. The Swan's own, from two landlords back, filed down inside so it poured short. Whoever hid it down here was protecting a dead man's name. |
| 9 | A small dog collar with a brass plate. The plate says GIP. It is older than Sixpence and Nan Caldwell has never heard of a dog called Gip. |
| 10 | A full set of somebody's teeth. Carved bone on a wire spring. Expensive. Missing since a funeral at which the corpse was noted to be smiling. |
| 11 | A purse with thirty-one coppers still in it. Rats do not spend. |
| 12 | A ledger page chewed at one corner. It is the Swan's cellar accounts for a year that the surviving ledger skips. The handwriting is the same. The page is not. |
| 13 | A gold signet ring cut with a swan over a bar. This is Barnaby Bly's, and the parish register says Barnaby Bly drowned upriver thirty years ago, unwitnessed, wearing it. A ring cannot come off a drowned man forty miles downstream and end up under a floor in Millbrook, and everyone the party shows it to will work that out at about the same speed. |
| 14 | A tortoiseshell hair comb, three teeth gone. Every woman in Millbrook over fifty has owned one exactly like it, which is why it has been down here fourteen years without being missed. |
| 15 | The old cellar key. The lock was changed twenty years ago because this went missing. The old lock was not thrown away. It is in the yard, still hung on the coal hole door. |
| 16 | A broadsheet thirty years old and worn through at the fold. It is the page carrying the drowning notice, and somebody carried it in a pocket for years before the rats got it. |
| 17 | A thimble with a hole worn through the crown. Useless to anyone. Somebody cried over losing it, and the person who did is still alive. |
| 18 | A locket snapped at the hinge, one pin missing. It is Hesta Dunmore's. Hesta Dunmore owns the mill, sits on the vestry, and reported this stolen the same week Barnaby Bly drowned. The missing hinge pin is in the midden too, about a foot away. It does not matter at all. |
| 19 | An unpaid rat-catcher's bill made out to the Crooked Swan. Dated eleven years ago, for work that was never done, signed Alvric Trencher. Trencher has been paid every year since to keep not doing it, and he will tell the party so for a pint, because he has been waiting a long time for somebody to ask. |
| 20 | A knot of hair in twelve colours, bound with wire. This one is not tribute and was not carried down here. The court made it. This is what a rat king's court does when it wants to make something like its king, and the party should be allowed to work out what that means on their own time. |
Nothing on this list is treasure. Two rows carry a number you could put in a purse: five gold on row 1 and thirty-one coppers on row 11. Everything else on the list is worth exactly what it is worth to the person who lost it, which in this town is a great deal more.
Every figure here was recomputed at encounter_xp.py rather than carried over from a draft. Target band levels 4-7, written at 5th.
The cellar, standing room. The Stop plus one Tithe-Swarm plus the Snuffers, in a room you can crouch in: raw 350 XP, adjusted 700 against four characters of 5th level, whose thresholds are 1,000 / 2,000 / 3,000 / 4,400. That is under the Easy line, and it is supposed to be. This is the control condition and the argument the whole pack is making: put this court in a room with headroom and it is worth less than an easy fight. Against four characters of 3rd level the same skirmish is 700 adjusted, Medium.
The midden, the full court. The King plus the Stop plus three Tithe-Swarms plus the Snuffers: raw 1,650 XP, adjusted 3,300 against the same four 5th-level characters. Hard. All six are present from round one, so that is the whole fight and not a back half. The Scream calls nothing and nothing arrives late: a summon would have made the number a lie.
The budget cannot see a ceiling. Six creatures at advantage against four characters at disadvantage, in the dark, at a third of their movement, is not what 3,300 adjusted usually feels like. Budget it as Hard and run it knowing it plays harder. If you want the printed number to be honest, fight it in the cellar.
There is no conversion table here. A challenge rating is a label a finished monster wears, not a monster you can swap in, so this pack scales the only honest way a four-block pack can: you field more or fewer of the same four printed creatures. Every row was recomputed at encounter_xp.py against a four-character party.
| Party level | You field | The full court |
|---|---|---|
| 4 | the King (CR 4) and the Stop (CR 1) | 1,950 adj. Hard |
| 5 (as written) | the King (CR 4), the Stop (CR 1), three Tithe-Swarms (CR 1/2), the Snuffers (CR 1/4) | 3,300 adj. Hard |
| 6 | the King (CR 4), the Stop (CR 1), five Tithe-Swarms (CR 1/2), the Snuffers (CR 1/4) | 4,625 adj. Hard |
| 7 | the King (CR 4), two Stops (CR 1), six Tithe-Swarms (CR 1/2), two Snuffers swarms (CR 1/4) | 6,600 adj. Hard |
Why the band stops at both ends. Below 4th, a CR 4 monster in a corridor where every attack against the party has advantage is not a hard fight, it is a funeral: run the cellar and leave the crawl alone. Above 7th, the servants are scenery and the King is a CR 4 creature that cannot move.
And the 4th-level row fields no swarms at all, so no Tithe and no Snuff. At 4th level this is a boss in a hole and a door with teeth, and the court is a thing they hear rather than a thing they fight.
Party size at 5th level. Three: the full court is 3,300 adjusted, Deadly (thresholds 750 / 1,500 / 2,250 / 3,300). Field two Tithe-Swarms rather than three for 3,100 adjusted, Hard. Five: as written it slides to 3,300 adjusted, Medium (1,250 / 2,500 / 3,750 / 5,500), so add a fourth Tithe-Swarm for 4,375 adjusted, Hard. Six: as written it is 2,475 adjusted, Easy (1,500 / 3,000 / 4,500 / 6,600), so field the 7th-level row's court, two Stops and six Tithe-Swarms and two Snuffers swarms, for 5,500 adjusted, Hard.
Two dials that move the fight more than the body count. Harder: put the midden at the far end of sixty feet of crawl rather than forty. Gentler: leave one lantern hook in the cellar the Snuffers cannot reach.
They flood the cellar. It works. The court leaves through the wall voids with what it can carry, the King drowns in its hollow because it cannot leave, and the party has killed the archive along with the thing guarding it. Grown Into the Boards keeps the King in the hollow; it was never written to keep it alive. Rows 7, 13 and 18 are now silt. Let this happen and do not fix it.
They burn the inn. Also final, and Nan Caldwell will remember which of them suggested it.
They try to buy it off. It works exactly once, on one swarm, and it is a wonderful moment: rats do not negotiate, but they do prefer bright things. No check. Take the offered object and remove one Tithe-Swarm from the fight permanently. Let the player feel clever, because they were.
They dig down through the taproom floor. Two hours of work and a great deal of noise turns the crawl into an open pit with standing room, which converts the encounter to the cellar's numbers. Reward it. The price is that all of Millbrook now knows there is a hole in the Swan's floor and something in it.
They bring the terrier. Sixpence goes into the crawl and does not come back out on her own. She is not a stat block and should not become one. She is a clock.
They tell the town. The moment the midden is public, four people want it filled in and one will pay for a fire. This is where the pack stops being an encounter and becomes the front half of a mystery, and you need nothing for that but the d20 and a straight face.
No numbers here are worth porting. Give the court three jobs (block the way out, kill the light, move the loot), make the crawl cost something your system already charges for, and put the hoard where a person has to lie down to reach it.
Three rows that are a conviction. The cuff, the ring and the locket are worth nothing and prove everything, and only together. Any one alone is a curiosity Hesta Dunmore can explain in a sentence.
Everything else belongs to somebody. Row 20 is the only thing the court made rather than carried, and rows 7, 13 and 18 are the murder, which leaves sixteen objects with sixteen owners, most alive and most in the same street. Handing them back is a week of small scenes and the best reason to keep a party in this town.
And Alvric Trencher's bill. Row 19 is the only object down there that names a living man who chose to leave it alone.
All original, built to the LIDM threat rails.
Large monstrosity, unaligned. Twelve rats grown together at the tails, thirty years in one hollow, and not one of the twelve has been alone since.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 16 (+3) | 8 (-1) | 12 (+1) | 5 (-3) | 16 (+3) | 6 (-2) |
Skills Perception +5 · Senses darkvision 60 ft., passive Perception 15 · Languages understands Common and cannot speak · Challenge 4 (1,100 XP) · Proficiency Bonus +2
Grown Into the Boards. The King's speed is 5 feet and it cannot willingly leave the hollow it occupies. It cannot be moved out of that space, knocked prone, teleported, banished or carried to another plane by any effect, whether that effect targets it, carries it along with another creature, or moves the ground it sits in. Destroying, burning, flooding or tearing out the structure around it does not move it either, and it is immune to being polymorphed. Tear up the floor and it is still there in the hole, looking at you.
Nothing Is Ever Destroyed. The King neither eats nor breaks nor buries what is brought to it. While it can perceive a creature that has taken an object out of the midden, that creature is the King's only target and the court's mark, and every creature of the court that is not holding a position attacks the mark in preference to any other creature. There is only ever one mark: if another creature takes an object out of the midden it becomes the mark and the one before it stops being one, and a mark that drops to 0 hit points stops being one with nobody replacing it until the King sees another object leave the heap.
Keen Smell. The King has advantage on Wisdom (Perception) checks that rely on smell. Putting out its light does not put out its eyes.
Multiattack. The King makes three Gnaw attacks.
Gnaw. Melee weapon attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) piercing damage.
The Scream (Recharge 5-6). The knot screams with twelve throats at once. Each creature of the King's court within 60 feet that can hear it may use its reaction to move up to its speed toward the King without provoking opportunity attacks, and it ignores difficult terrain until the start of the King's next turn. Each creature within 30 feet that is not of the court and can hear the scream must make a DC 13 Constitution saving throw or be deafened until the end of its next turn. The Scream is an action: a King that screams does not Gnaw that turn.
Medium beast, unaligned. A rat so old and so fat that the ratters stopped trying to kill it and started using it.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 14 (+2) | 12 (+1) | 14 (+2) | 3 (-4) | 12 (+1) | 5 (-3) |
Skills Athletics +4 · Senses darkvision 60 ft., passive Perception 11 · Languages none · Challenge 1 (200 XP) · Proficiency Bonus +2
The Stop. A stop is what a rat catcher plugs a bolt-hole with, and this one plugs its own. While the Stop occupies a gap, crawlway or doorway no more than 5 feet wide, any creature can move into and through its space as though the Stop were an ally, and the Stop can move through any other creature's space on the same terms. No creature but the Stop can end its move in that space, so a creature entering has to have the movement left to leave again, and a creature forced into that space does not stop there either: put it back in the square it was pushed from. It costs no more to cross than any other square of the same ground: going into the crawl that is 15 feet to enter and 15 to leave, which is a whole turn of a 30-foot speed.
Made for the Runs. In a crawlway too low to stand in, the Stop is neither prone nor squeezing. It moves and fights at full speed and pays none of the crawl's costs. It was born in them.
Keen Smell. The Stop has advantage on Wisdom (Perception) checks that rely on smell.
Anchor Bite. Melee weapon attack: +4 to hit, reach 5 ft., one target. Hit: 9 (2d6 + 2) piercing damage, and a Medium or smaller target is grappled (escape DC 12). The Stop can hold only one creature grappled at a time, and while it holds one it does not move, because moving is not what it is for.
Nobody Goes Past. When a creature tries to enter the Stop's space, or is pushed into it, the Stop makes one Anchor Bite against it first. On a hit, the creature's movement ends and it stays in the space it came from, and it is grappled only if the Stop's jaws are free. The Stop has one reaction a round like anything else, so it cannot also take an opportunity attack, and four characters going past it one after another are four attempts against one reaction.
Its damage sits at the floor of its band on purpose. It is a door, not a weapon, and it is paid for in rounds the party does not get to spend elsewhere.
Medium swarm of Tiny beasts, unaligned. The working caste. They are not trying to kill anybody and they never have been.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 9 (-1) | 14 (+2) | 12 (+1) | 2 (-4) | 12 (+1) | 4 (-3) |
Damage Resistances bludgeoning, piercing, slashing · Condition Immunities charmed, frightened, grappled, paralysed, petrified, prone, restrained, stunned · Senses darkvision 30 ft., passive Perception 11 · Languages none · Challenge 1/2 (100 XP) · Proficiency Bonus +2
Swarm. The swarm can occupy another creature's space and vice versa, and it can move through any opening large enough for a Tiny rat. In a crawlway too low to stand in it is neither prone nor squeezing and pays none of the crawl's costs. It cannot regain hit points or gain temporary hit points.
Keen Smell. The swarm has advantage on Wisdom (Perception) checks that rely on smell.
Bites. Melee weapon attack: +4 to hit, reach 0 ft., one creature in the swarm's space. Hit: 10 (4d4) piercing damage, or 5 (2d4) piercing damage if the swarm has half its hit points or fewer.
Tithe. The swarm goes through the belongings of one creature in its space. One object that creature is carrying is at stake: 1 pound or less, not worn and not held. If the creature can see the swarm it picks which object. If it cannot, it does not get to pick: the swarm takes the last object that creature used or put away, and if there has not been one yet, any object of the DM's choosing that qualifies. The creature then makes a DC 11 Dexterity saving throw. On a failure the swarm takes the object and the creature knows at once that it is gone; on a success the swarm gets nothing. A swarm carries what it has taken in its bodies: kill it and everything it holds drops in its space, where anyone can pick up one object with a free object interaction, and a swarm that gets away with something has it in the midden by morning.
It opens on whoever is nearest the hoard rather than whoever is most dangerous, which is the tell that gives the party the whole pack.
Medium swarm of Tiny beasts, unaligned. Smaller and faster and interested in wax rather than in people.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 6 (-2) | 14 (+2) | 10 (+0) | 2 (-4) | 12 (+1) | 4 (-3) |
Damage Resistances bludgeoning, piercing, slashing · Condition Immunities charmed, frightened, grappled, paralysed, petrified, prone, restrained, stunned · Senses darkvision 30 ft., passive Perception 11 · Languages none · Challenge 1/4 (50 XP) · Proficiency Bonus +2
Swarm. The swarm can occupy another creature's space and vice versa, and it can move through any opening large enough for a Tiny rat. In a crawlway too low to stand in it is neither prone nor squeezing and pays none of the crawl's costs. It cannot regain hit points or gain temporary hit points.
Tallow-Fed. These rats eat wax, wick, tallow and lamp oil. The swarm moves toward the brightest nonmagical flame it can perceive and attacks the creature carrying it only if that creature is in the way. It is not clever, it is not adaptive, and a party that works this out can use it. If it can perceive no flame it could put out, magical light included, it moves instead into the space of whatever creature the King has marked and uses Bites, and if the King has marked nobody it shares a Tithe-Swarm's space and bites whatever that swarm is working on.
Bites. Melee weapon attack: +4 to hit, reach 0 ft., one creature in the swarm's space. Hit: 5 (2d4) piercing damage, or 2 (1d4) piercing damage if the swarm has half its hit points or fewer.
Snuff. One nonmagical open flame in the swarm's space or within 5 feet of it goes out: a candle, a torch, a rushlight, a lantern (they get in through the shutter), a fire no larger than 1 foot on a side. If a creature is holding or wearing that light source, it must succeed on a DC 11 Dexterity saving throw or the flame goes out anyway. Magical light of any kind is unaffected, and so is a fire bigger than the swarm.
I write these because 30+ years of real tables has taught me that the monster nobody remembers is the one that fought in a room with the lights on.
Gnasher's Grimoire is the free browser toolset these Keepers install into, and it lives on itch. All four blocks and the d20 drop straight in. Take a free adventure while you are there: Twelve Good Names is a complete one-shot for four 3rd-level characters, and The Night Watchman is a solo adventure you can play in a browser tonight.
Free drops land Thursdays and Saturdays.
Long Island Dungeon Master. The monsters are mine. 30+ years of real tables.
This work includes material from the System Reference Document 5.1 by Wizards of the Coast LLC, available under the Creative Commons Attribution 4.0 International License. Every stat block, name, table row and rule in this pack is original text released under CC BY 4.0. What is taken from the SRD is the mechanics (the swarm package, the prone and grappled conditions, squeezing, saving throws, and the encounter-budget math), which is not copyrightable expression.
Auto-built from every data-dc, data-hp, stat block, preset clock and pre-loaded combatant in this file. Prints on its own sheet.
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