The Thing Beneath the Floor
The floor of this hall is one continuous sheet of bronze, eighty feet on a side, and it is not a floor. It is a lid. Twelve pins the length of a man's leg ring its edge in stone housings, and five of them have come up out of their sockets and lie where they fell.
Four people in grey are working on the sixth. They have a maul between them and they are very tired and they have been doing this for a long time.
Through the gap where the fifth pin should be, an arm comes up. It is grey, it is nine feet long, and it is holding a lamp — carefully, upright, so as not to spill it. It sets the lamp down on the bronze and withdraws, and a voice comes up through the floor, unhurried and quite kind.
"You have brought your own. Then take mine as a gift. Would you tell me your names?"
DM summary. One of the Hundred-Handed, bound under this floor since before Knossos, and courteous about it. It cannot be killed, damaging it loosens it, and the four exhausted people trying to hold it down are not your enemies unless you make them.
The Boon
The Cold-Forged PinOptional item
A maker's spare that seats where no cast pin will, and buys one arm out of one gap
What it is. The Cold-Forged Pin is a bronze bar the length of a man's leg, tapering to a blunt chisel, its head mushroomed flat under a great many old blows. It was worked cold and slowly, the way the first crew worked, nothing like the cast replacements on the Cult's rack: darker, denser, stamped below the crown with a mason's mark.
Where it comes from. Plant it early as metal, not an heirloom: behind a workshop bench of broken moulds, on a loot roll as thirty-four pounds of scrap, or in a dead engineer's canvas roll. Let a player weigh it and keep it anyway. Late plant: at the back of this hall's own pin-store, set apart from the eleven cast pins the Cult uses, because three generations have kept it apart without knowing what for.
What it does here. Eleven cast spares cover eleven ordinary sockets and one thing they cannot cover: a housing stripped, split, or widened past the point where a cast pin will bite. Nothing else in the hall seats in that hole. The Pin does, once, because it has the original taper — so a Take the Floor through a housing, or a pin that goes down a gap and does not come back, stops being a socket the party can never fill. Driving it costs what any pin costs: an action, the maul, Strength (Athletics) DC 15 or Thieves' Tools DC 16, Feel the Hammer drawn, the Loosening −2. It also buys two words. The mark on it reads to anything that knows the work as one of the makers, so the Cult will work alongside the party without being talked into it; and once, held out over a gap, it asks as a smith and that arm withdraws — no 60 damage, no DC 17 Strength shove, no 25-damage round adding 2 to the Loosening.
What it doesn't do. It is one pin and there are twelve. It reads no mosaic, drives nothing by itself, seats no faster, moves no arm twice, and does nothing to the ten-count. It is not a weapon. A party who never found it runs this room as written, because the puzzle as written never strips a socket — the Pin answers a bad break, not the encounter.
Card and numbers or jump to the card ↓
Arena
Battle map: The Great Hall — pages 29 & 30, 110 × 75 ft
The great hall reads as the lid chamber: the central chequer is the 80 × 65 ft bronze lid (say it rings underfoot), and the printed stepped border is the gallery, 10 ft up with its corner stairs. Number the twelve pins clockwise around the border and mark the five that are sprung.
- Dimensions. 92 ft × 71 ft overall, ceiling 20 ft: a bronze lid of 80 ft × 65 ft with a stone gallery 10 ft up on three sides of it, 6 ft deep, reached by stairs at each corner. The party enters at gallery level and looks down at the lid. Everything that matters is either on that plate or ten feet above it.
- Light. Two braziers on the gallery, dim over the lid, plus the lamp the Thing set down, which nobody wants to pick up.
- The lid. Bronze plate over a void of unknown depth. Sound carries through it; so does warmth. Standing on the lid is the dangerous choice and the room should make that obvious in the first thirty seconds.
- The twelve pins. Numbered clockwise in the mosaic border, one to twelve. Seven are seated. Five are sprung: 2, 3, 7, 8, and 11. Each sprung pin is a gap wide enough for an arm. Round a border this size they sit about 24 ft apart, which is the arithmetic the whole encounter runs on: one pin over is a single move with the action still in hand, and two pins over is not.
- The mosaic border. A knot pattern runs the full circuit, and it is a diagram, not decoration: it pairs each number with the one opposite it. This is the answer to the puzzle and it is underfoot where anyone can read it.
- The maul and the pin-store. A twenty-pound bronze maul chained to the north gallery rail, and a rack of eleven spare pins beside it. The Cult keeps its tools where they can be found in the dark, because they have had to.
- The listening posts. Four bronze horns set into the gallery floor, mouth down, that the Cult uses to hear which quarter is failing. A character with an ear to one knows which pin will spring next, one round in advance.
Roster & Budget
Four tired people, and a thing that is not on the budget because it cannot be killed.
| Count | Creature | XP each |
|---|---|---|
| 3 | Thread-Warden | 1,100 |
| 1 | Knossian Priest of the Thread | 1,800 |
The Cult is 5,100 base; ×2 for four bodies = 10,200 adjusted — and only if they turn hostile, which is entirely the party's choice. Against the APL 9 Deadly budget of 14,400 that is well short, and it is meant to be, because the encounter is not them.
The Thing is priced as the arena. Six arms on the board at any moment, each AC 16 and 60 hit points, a heave that puts the whole party prone, a grapple that drags toward a gap in the floor, and a ten-count clock running the whole time. Treat it as a Deadly hazard worth the missing 4,200 and then some. It has a CR of 13 for scaling purposes only; do not award it, because nobody is going to kill it.
Phases / Clock
The Loosening. One counter, visible to the players — put ten tokens on the table and take them away. It starts at 0 and rises:
| Trigger | Loosening |
|---|---|
| End of each round | +1 |
| Each pin that springs or is pulled | +1 |
| Any round in which the Thing takes 25 or more damage | +2 |
| Each pin correctly driven | −2 |
| The Cult working uninterrupted for a full round | −1 |
At 7 the lid lifts an inch all the way round and every light in the room bends toward the gap. Say so. That is the warning and the players get it in time to change their minds.
At 10 it is out. Do not run that as a party wipe: it stands up, the hall comes down, and everyone runs. The Resolution is then played as an escape with the maze collapsing behind them (borrow X12's shape), the party gets out, and the Labyrinth survives with a hall fewer. Nobody is punished with a dead campaign for a bad decision made honestly.
Phase change — When It Notices. The moment a creature attacks it, or refuses to speak to it two rounds running, it stops being a guest. Visibly: all six arms come out at once, the lamp goes over, and the voice stops being kind and starts being patient, which is worse.
Combat Resolution
Required, and it is a holding action, not a kill. Six to ten rounds.
- Round 1. It asks for names. Let the players decide, in character, one at a time. Anyone who answers is safe from it for the rest of the encounter and has given a Hundred-Handed One their true name, and the DM should write that down where the player can see it being written down.
- Fighting the arms works, briefly. An arm at 0 hit points withdraws and another comes up through a different gap at the start of the next round. Every 25 damage in a round adds 2 to the Loosening, so a party that goes all-out on the arms is racing itself.
- Tactics. It grapples and pulls toward gaps. It does not crush and it does not kill: a creature dragged to a gap is held at the edge, half in, and can be pulled back by an ally with a Strength (Athletics) DC 17 check or by dealing 20 damage to that arm. It is not trying to eat anybody. It is trying to get its shoulder through.
- The Cult fight only if the party attacks them, cuts a thread, or works on the pins in a way that will spring more. The Priest calls terms the moment two wardens are down, and its terms are worth taking: help us for six rounds and we will show you the way out. A party that fights them wins a 10,200-XP fight while a ten-count runs, which is the single worst plan available in this room.
- What winning by fighting looks like: every arm on the board driven back at the same moment, and the party gets one round in which no arm is up. That round is worth two pins. Winning here means finishing the binding, and there is no other victory available.
Alternate Resolution
Puzzle — drive the twelve pins. This is the primary path and it is the only clean win.
Reading the pattern. The mosaic border pairs each pin with the one opposite: 1–7, 2–8, 3–9, 4–10, 5–11, 6–12. The binding takes a sprung pin and then its opposite, and it will not take two adjacent pins in a row. With 2, 3, 7, 8 and 11 sprung, the order that works is 2, 8, 3, 9 (which will spring when 3 goes in), 7, 1 (likewise), 11, 5 (likewise) — in short: drive a sprung pin, then immediately drive its opposite, and expect the opposite to have sprung by the time you get to it.
| Element | Value |
|---|---|
| Reading the mosaic | Investigation DC 14, or Religion DC 15 on the knot-work, or free to any character the Cult has agreed to work with — they will simply tell you |
| Driving a pin | One action with the maul and Strength (Athletics) DC 15, or Thieves' Tools DC 16 with a jack. Two characters on the maul: no check |
| Driving out of order | The pin seats and a different pin springs. Net Loosening +0, and a round gone |
| Driving with an arm through that gap | Not possible. The arm must be driven back first — 60 damage, or a Strength DC 17 shove against it |
| Solved state | All twelve pins seated. The lid settles half an inch with a noise like a struck bell, the arms withdraw, and the voice says "Ah." Nothing else happens, and that is the win |
Doing it with the Cult is twice as fast: they carry the pins, they hold the maul, and the Priest's blessing gives the driver +2 on the check. Persuasion DC 13 is enough to get them to work with the party — they are exhausted and they have been alone with this for three generations. Attacking them first makes the room forty per cent harder and the Priest will say so, out loud, while it fights.
If the party carries the Cold-Forged Pin, you can afford to let the room break something. An arm that reaches up and takes a pin down the gap, or a housing that finally gives up under a Take the Floor, stops being a hole the party can never fill and becomes one bad round they have an answer for — and the answer costs them the same action, the same DC 15, and the same reaction from below as any other pin. Show the Priest the maker's mark before you ask for the Persuasion DC 13, and do not ask for it. Three generations of holding this floor down and none of them has ever seen the original work.
The escape branch. If the Loosening reaches 8 and the party has fewer than four pins to go, they may cut and run instead: everyone off the lid and out through exit A, one Dexterity save DC 15 each as the floor heaves. Getting out alive is a win here and the text should say so — content spec §7.3 lists escape as a legitimate non-lethal condition, and F07 is the entry that means it.
Persistence Check
Non-lethal only, and here is the win condition in one sentence: seat all twelve pins, or get everyone out of the hall alive.
- What it is. One of the Hundred-Handed, or as much of one as would fit under a floor. Content spec §9 puts the Hekatoncheires on the do-not-kill list without qualification, and this is the entry that list was written for.
- If the party tries to kill it anyway: they cannot, and trying is actively how they lose. It has no hit point total. Every arm destroyed is replaced next round. Every round in which it takes 25 or more damage adds 2 to the Loosening, so a party that commits to damage as a strategy will free it in five or six rounds and then be running for the exit through a collapsing hall. Say this to the table at the first arm they drop: "It doesn't seem to mind."
- No world-ending release. Even at Loosening 10 it does not get out into the world. It gets a shoulder and an arm out, this hall folds, and the maze seals it under a different roof. The Labyrinth survives; a section does not. That is the same boundary X12 works inside.
- Table safety. This room is being held down, dragged under a floor, and something enormous in the dark that talks. If any of that is on the table's no list, run it with the arms as bronze machinery rather than flesh — Daedalus's binding engine straining at its bolts — and every mechanic above still works unchanged.
Scaling — APL 6 / 12 / 15
| APL | Adjustment |
|---|---|
| 6 | Three pins sprung instead of five, four arms instead of six, arms at 40 hit points, and the Loosening runs to 12. Two Thread-Wardens, no Priest. DCs −2 |
| 9 | As written |
| 12 | Seven pins sprung, arms at 75 hit points, Loosening runs to 9, and Take the Floor recharges on 4–6. Four Thread-Wardens and the Priest. DCs +1 |
| 15 | Nine pins sprung, eight arms, arms at 90 hit points, Loosening runs to 8, and a second phase at Loosening 5 where a second voice starts answering from under the lid and the party has to work out which one is telling them the order. DCs +3 |
Exit to the Resolution
Boon Card
The Cold-Forged Pin
Wondrous item, rare · a binding-pin from the original crew, cold-worked and marked · optional, and never on the loot table
AC 19, and nothing a ninth-level party carries will break it | Weight 34 lb | Attunement none
Appearance: bronze, four feet, square in section, blunt chisel point, head mushroomed flat, a mason's mark of two crossed lines and a dot below the crown
One Pin, Once. It is a single pin. Driven, it stays driven, and nothing available in this encounter draws it back out of a socket. It does not come with a maul, a jack, or an arm to swing either.
Seats Where Nothing Else Will. Cold-worked to the original taper. It holds in a housing that has been stripped, split, or widened past the point where a cast replacement will bite, and it stands in for any binding-pin that has been dropped through a gap, carried off, or never made. This is the whole of what it is for.
Driven Like Any Other. One action with the maul and a Strength (Athletics) DC 15, or Thieves' Tools DC 16 with a jack, or no check at all with two characters on the maul. It draws every reaction an ordinary pin draws and it moves the Loosening the same 2 points. It is not faster and it is not safer.
Maker's Mark. Anything that knows the work reads a creature carrying this openly as one of the makers rather than one of the keepers. The Cult of the Thread will work alongside such a party without being persuaded to, and the Thing Beneath the Floor addresses the bearer by trade instead of asking it for a name.
Not a Weapon. Improvised: 1d6 bludgeoning at disadvantage, two hands, and a swing that leaves the wielder wide open. Thirty-four pounds of bronze is worth more in a socket than in the air.
Ask as a Smith. Once per encounter, the bearer holds the pin over a gap and asks the bound thing to take its arm out of the way. It does: that arm withdraws until the start of its next turn, with no check made, no damage dealt, and no rise in the Loosening, and it says something about the hands that made the pin while it goes. It grants this once, for the pin, and not again.
Creature Cards
The Thing is this finale's only inline card. The Cult of the Thread (W18) recur across the deck, so their numbers live in the bestiary; three generations of holding this floor down stays here.
Shared across rooms, so the full cards live in the bestiary: Thread-Warden, Knossian Priest of the Thread. Every mention above opens the numbers here on this page.
The Thing Beneath the Floor
Gargantuan aberration, lawful neutral · CR 13 (10,000 XP) — reference only; it cannot be killed
AC 16 (grey hide) | HP 60 per arm, six arms up at a time; the body is under the lid and unreachable | Speed 0 ft., reach 20 ft. through any gap
Saves Con +12, Wis +9 · Details Insight +9, Perception +9, Persuasion +10 · Immune to poison damage, psychic damage · Immune to blinded, charmed, exhaustion, frightened, prone, stunned · Blindsight 120 ft. through stone · Speaks every language spoken above it
Cannot Be Killed. It has no hit point total and no death. Arms reduced to 0 hit points withdraw and are replaced at the start of its next turn through a different gap. Nothing in this encounter, and nothing a ninth-level party carries, ends it. The win condition is the twelve pins or the door.
The Loosening. A counter from 0 to 10, tracked in the open. It rises by 1 at the end of each round, by 1 for each pin sprung, and by 2 in any round in which it takes 25 or more damage. It falls by 2 for each pin correctly driven and by 1 for each full round the Cult works undisturbed. At 10 it gets a shoulder through and the hall comes down.
Courteous. It takes no hostile action against a creature that has spoken to it since the end of its last turn, and it answers questions truthfully, including the ones about what it is and what it will do if it gets out. It is not lying, it is not bargaining in bad faith, and it is not less dangerous for either of those things.
Collects Names. A creature that tells it a true name is never attacked by it again during this encounter. It keeps the name. What that costs is not settled tonight and the DM should let the player feel the weight of it rather than pricing it.
Feels the Weight. It knows the exact position of every creature standing on the lid, through the lid, and it knows which of them is holding the maul.
Multiattack. Three grasp attacks, from any three arms currently up.
Grasp. Melee, +12 to hit, reach 20 ft, one Large or smaller creature. Hit: 16 (2d10 + 5) bludgeoning damage, and the target is grappled (escape DC 17) and dragged 10 ft toward the nearest gap. A creature dragged to a gap is held half in it, restrained, and can be pulled clear by an ally with a DC 17 Strength (Athletics) check or by 20 damage dealt to that arm.
Take the Floor (recharge 5–6). It pushes up with everything at once. Every creature on the lid makes a DC 17 Dexterity saving throw, taking 18 (4d8) bludgeoning damage and falling prone on a failure, or half as much and no fall on a success. One seated pin of the DM's choice springs.
Offer. An arm sets an object on the bronze within reach of a creature and withdraws: a lamp, a bronze helm, a child's sandal, a coin of a mint nobody uses. It has had a very long time to collect things and it gives them away freely.
Feel the Hammer. When a pin is driven within 40 ft, one arm makes a grasp attack against the creature that drove it.
Reach (costs 1). One withdrawn arm comes up through a different gap and makes one grasp attack.
Say Something Kind (costs 1). It addresses one creature within 60 ft by whatever it has learned of them. That creature makes a DC 18 Wisdom saving throw or cannot take a hostile action against the Thing until the end of its next turn.
Heave (costs 2). Every creature on the lid makes a DC 17 Dexterity saving throw or falls prone, and the Loosening rises by 1.