51 Black Doors

In Ben Robbins' original West Marches campaign, some parts of the dungeon were dramatically tougher (but more lucrative) than others:

Dungeons generally had the same or near encounter level as the region they were in (for all the obvious reasons), but to make things interesting I designed many of the dungeons with “treasure rooms” that were harder than the standard encounter level, well hidden, or just plain impossible to crack. So even when a party could slog through and slaughter everything they met, there was a spot or two they couldn’t clear, whether it was the fearsome Black Door, the ghoul-infested crypts of the ruined monastery, or the perilous Hall of Swords. They usually had to give up and make a strong mental note to come back later when they were higher level.

Lots of times they never came back. They really wanted to, they talked about it all the time, but they never got around to it because they were busy exploring new territory. Rather than being frustrating each new “incomplete” seemed to make players even more interested in the game world.

Was there actually good treasure in the treasure rooms? Yes, really good treasure. Every time the players cracked one it just made them more certain that all those other sealed or well-guarded rooms they couldn’t beat were chock full of goodness.

I was in the mood for brainstorming some 'black doors', and here's what a bunch of creative folks came up with:

d%	What bars the adventurers' way?
1-2	A slab of black granite, positioned like a door but actually built in place. It extends several feet into the surrounding masonry.
3-4	A trap door at the top of a long natural chimney--above it is a room filled with ghouls (dozens) that walk back and forth over the trap door.
5-6	A 20' section of corridor, the floor is literal lava. It's flowing from a rent in one wall and draining through a wide cracking I to a chamber below.
7-8	A door of gnarled and bulbous vigorous oak. Every attempt to chop it causes it to sprout extra thickness.
9-10	A gale force wind that howls down the corridor extinguishing all natural flames.
11-12	The opening in the top of the chamber is smooth and slopes upwards, like a reverse whirlpool. Acidic oozes drip along the surface.
13-14	A sphere of annihilation blocking a corridor. On the ground nearby, many skeletons missing a head or arm or more.
15-16	An aquarium, positioned like a door. It is filled with water and anti-pufferfishes (they are full of explosive gas that ignites as soon as they are not in water anymore). One glass pane is super thick and can be drilled while the one on the other side will shatter as soon as it is hit or pierced.
17-18	A door of living wood that grows thorny arms and claws to tear the flesh of anyone who comes close.
19-20	A door rooted into the living rock around it, made entirely of a solid plank of magically treated trollbone. Any attempt to penetrate it rapidly spawns one or more angry, confused trolls with (healing) wounds from the tools. Meanwhile the door itself heals itself from the power of the mountain and borrows the rock's invulnerability to acid and fire.
21-22	A reverse gravity spell that makes you fall onto the stalactites at the ceiling, 100+ ft above.
23-24	A glassy abyss that quickly shears ropes.
25-26	An open archway, flanked by silent statues, gazing down on the path between. Anyone who passes between is vapourized by energy beams fired from the eyes of the statues. (Lifted wholecloth from The Neverending Story.)
27-28	The veins of metal collect here into a single polished mirror. Anything that goes in instantly comes out. Any spell or object thrown, any individual that goes in walks right back out. Any mirror carried through is instantly rendered opaque.
29-30	Seven buttons must be pressed at the same time to open the door. Each is encased in a heavily enchanted portal in the room, locked tight and wreathed in a curse or elemental trap.
31-32	A frictionless corridor that gently slopes upwards. 80' long.
33-34	An oily pool surrounded by glowing stones. One stone is taller than the others and covered in glyphs, and acts as a control.
35-36	A series of climbs and falls through a long hallway, 30' high, with small locked doors at the top and bottom. The top 15' is bathed in positive energy, the bottom 15' in negative energy. See Planescape elemental planes for effects.
37	A 40x40x40' room; the entrance is a small round opening in the dead middle of the ceiling.
38-39	A petrified gelatinous cube blocks the corridor. Its semi transparent carcass still holds some treasure, and can allow you to see the movement of indistinct shapes and light on the other side. How did the gelatinous cube wind up in such a fashion? A rare disease or some magic? Would stone to flesh return it to normal?
40-41	An earthquake has caused the stone to shear - a 10' wide corridor has been offset by 9'10" leaving only a two-inch gap.
42-43	An empty stone arch sits at the bottom of the dungeon, rune-rimed and inert. Ancient writing covers the walls, describing a ritual, a portal - but those who study them are compelled to leave.
44	A small labyrinth where the dead ends are formed by grills of heavy iron bars. Deadly oozes move through them unimpeded, and take the shortest path toward living creatures.
45-46	100' corridor ends in a room. In the room is a crackling metal globe on a post. Occasionally, lightning cracks off the globe and hits the wall of the room. It also zaps the nearest thing in corridor with lightning once every five to ten seconds.
47-48	An area of the room (e.g. the ceiling) is actually a powerful magnet that draws all ferrous material to it. Not even a storm giant is strong enough to dislodge it (though he could certainly create an offsetting electric field...). Not as useful vs. bronze age technology.
49-50	A 100', pitch dark hallway of trip wires and pits ends in a door with a detailed demonic face twisted in rage. The door causes fear in any who lay eyes on it - the power of the fear is greater the more clearly the face can be seen. When dim torchlights merely brush its shadows, it's just a sense of imminent and growing doom, but in full light the intricate details of its horrors can be seen and inspire a panicky flight in those who behold it. The door is not locked.
51-52	A wall of seemingly impenetrable glass stands before you, treasures beyond your imagining lay just on the other side.
53-54	This looks to be a dead end, save for the tiny opening at the bottom of the wall, just wide enough to fit an arm through.
55-56	A small, naked -- androgynous and neuter -- humanoid figure with mayfly wings and glittering white skin sits in a diminutive high backed velvet armchair reading a book. Calmly addressing the party, it looks at them with black, void like eyes and speaks in a hauntingly beautiful voice, "Welcome. I am the door of black. Do you have my key?" The book and chair are illusions, and the powerful fey wields unlimited spheres of annihilation in the same way a child would throw rocks, plucking them out of thin air. If attacked, the first action is to simply eliminate the weapons used and calmly respond, "No, young one, that is not the key."
57-58	Reverse door: The treasure mcguffin / thing you've been sent to recover can be reached with relatively little difficulty, but it is mystically tethered to the room or the dungeon, impeding your escape. This could manifest in a few ways. The object grows in weight with each step you take. Its weight is tracked per person based on how many 5' or 1m squares they travel with it item while in the dungeon. The doors all close and you must find a way to open them all. Roll d20 on this chart for each "door". Reroll this result. There is a literal tether attached to it, but you can only see it with detect magic / see invisible or similar. It can't be broken by brute strength.
59-60	The corridor is split by a ravine 18' across. The inner walls of the ravine are soft and porous, and crumble easily.
61-62	Giant stone golems surrounded by anti-magic cloud.
63-64	A pool of liquid, 30' wide, with a 30' high ceiling. There is a very narrow and slippery path around the pool. In the centre of the ceiling there is a hole with a ladder that leads to the next room. You barely see the ladder from the edge of the room. The liquid in the pool feels greasy like soap and is much, much less dense than water. It weighs next to nothing. Wood floats, but just barely. People sink dramatically.
65-66	A submerged passageway, too long for a swimmer to simply hold his breath.
67-68	A wide chasm, 100' or more across, filled by giant spider webs, with a narrow plank bridge set in the webs themselves. The webs are occupied, and burning them removes the plank bridge as well.
69-70	A literal black door, haunted by the souls of every PC and hireling who has died in the dungeon. If any bear a grudge the door is held shut; if all are satisfied with the surviving party it opens freely. Accusatory wails give clues to how they can be appeased.
71-72	A collapsed tunnel requiring reasonable engineering skills, a block and tackle, sweat, and a lot of wood to clear and shore up.
73-74	A corcscrewing and twisting mile long, 2 foot high tunnel, very warm, filled with stinging ants.
75-76	A few friendly but quite strict museum guards or park rangers with views on poaching and interfering with exhibits.
77-78	A hallway that is incinerated with flame every 30 seconds. Usain Bolt could run across it in 31 seconds.
79-80	Motherfucking pool with a couple of submerged froghemoths. Eyes visible. Get across it.
81-82	Another standard: just a big-ass descent. Better come back with 500 feet of rope (and not the cheap stuff, because the cheap stuff will break if it has to hold up 500 feet of heavy hempen rope).
83-84	A long tunnel. Like 50 miles long, devoid of water.
85-86	Wall of fire. Come back with the sigil of Eldrune, an anti-fire spell, or just more hit points.
87-88	A door of sacrifice, with an obvious sacrificial altar mouth, that requires the brain of a sentient creature. The door is also some sort of punchy, fighty golem thing.
89-90	The classic puzzle thing, e.g. a portal of burning flames that deals 66 hp damage to everyone passing through, except those who are completely naked. Above, an inscription, "Leave your mother. The world awaits." or some other stuff like that.
91-92	A metal door in an echo prone room where unsavory creatures sleep. I'm thinking batfolk goblins on the ceiling, or a swarm of styrges, or drowsy zombies. More than an average party can comfortably deal with.
93-94	The door is a bit more difficult to break down than normal, and it cannot be done fast without magic. Most mundane attempts will awaken the monsters.
95-96	A set of runes written in paint; anything not flesh becomes immaterial if it gets within 10 feet.
97-98	A wailing door. It's cries can be deafening and responds violently to any interaction with it. Unknown to the party, it just needs to be sung to sleep.
99-100	A blind and somewhat senile ancient Beholder whose eye-bolts still function -- or, most of them do, or some of them have random effects due to experiments the Beholder attempted on itself. Does it still have a full mouth of teeth?

Skerples was in the mood to get through some of these doors with a small party of 1st level adventurers, and posted how they would go about it along with a review of some doors he didn't like. It's a fun read!

A few notes in response to the responses I've seen floating around. None of this is conceptually new! I was reminded that 'gating' is an old concept from video game level design--familiar from 'you need the red key card' situations.

Obstacles also serve lots of different purposes, depending on how they're written.

• You can have very constrained railroady things that try to force players to do a side quest first (the aforementioned, 'fetch the red key card').
• Similarly, you could have gates that are puzzles which the designer wants the party to solve in a particular way, with railroady dissuasion of alternate solutions.
• You can have gates that are meant to act as filters to guarantee that characters have specific abilities or pieces of equipment (which can also be a bit railroady).
• The gate might be serving primarily as a marker to the players that the ecosystems/dungeon fauna on either side could be dramatically different--in the same way that mythic underworld entrances do. Perhaps bad stuff has been sealed in.
• The gate might just be an obstacle which demands the players invent a solution (but without prescribing what that is), an old-school staple.
• Some doors could be all of these things - a door with powerful active defenses (e.g. lightning) that blasts away at parties who don't have the red key card (but tough, magically defended might be able to slog through and defeat the door directly), but which even determined and inventive (e.g. by hiring a team of miners and tunneling around the damn thing).

Doubtless there are more!

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Many thanks to: Adam "Bison Court" D, Andrew Muttersbach, Ara Winter, Arnold K., Brent Newhall, Brian Lee, Brian Murphy, Claytonian JP, Dave R, Eric Nieudan, Evan Edwards, Follow Me, And Die!, James Shields, Jason Abdin, Jean-François Lebreton (Jarnos), Jesse Alford, Jesse Cox, Luka Rejec, Matt Kay, Michael Atlin, Mike Edwards, Perttu Vedenoja, Rob Brennan, Skerples, William Altman, William Benjamin John Davis (SinbadEV) .. for their contributions.