The 10 types of special rooms

"A Special is anything not exactly a trap, but placed for special reasons." Moldvay Basic pg. B52

Traps, monsters, secret doors, and treasure all cohere into continuous flows of challenge/reward and mystery/discovery. Special rooms, on the other hand, largely stand apart from these conventional elements while also replicating them in miniature: drinking from the magic fountain might raise an ability score but it might also make you vomit bees for the next minute. The elevator that takes parties from the first to the sixth floor and locks behind them might be a death sentence for new PCs but incredibly valuable for high-level adventurers. 

The purpose of this exercise is to categorize common forms of "Special" rooms found in old school-style dungeons. 

While the point of special rooms is to have bizarre, unique dungeon set pieces that defy expectation, having a list of common forms might help DMs come up with new ideas, or new ways to approach conventional ones. 

A trio of caveats: 

1. This is not intended to categorize the specific contents of special rooms (fountains, statues, etc.), but rather different meta-categories of special room.
2. Special rooms may have two or more categories layered atop one another; i.e. the reward of a puzzle room may be transit to another part of a dungeon.
3. These categories are not exclusive to special rooms—monster lairs, traps, and other kinds of rooms can also incorporate elements from this list. 

Anyway there are 10 types of special rooms

1. Random Effect
2. Experiment
3. Alter Environment
4. Exchange
5. Side Quest
6. Puzzle 
7. Minigame
8. Transit
9. Trick
10. Curiosity

Random Effect 

• The room with the magic pools from In Search of the Unknown. 
• The room with the magic stone, also from In Search of the Unknown.
• A white tree bearing opalescent berries; eating one imparts a random boon or bane
• A strange monolith covered in glowing runes of various sizes and colors. Each one does something different when touched. 

Random effect rooms offer players an opportunity to interact with something and roll on a table to see what happens. Alternate version is when there are multiple things to interact with and each one has its own effect. In both cases, the effects are unknown to the players and the general assumption is they are figuratively rolling the dice to see what happens. This is the OSR DM’s fast ball. The most fundamental special room, and the perfect crystal distillation of the OSR “play to find out” ethos. All you need is a random list of oddball effects and a distinctive set dressing to frame it and you’re all but guaranteed a memorable table experience. 

Not every kind of dungeon needs a room like this, but every dungeon has space for one. However, much like the fastball, it can get stale if you use it too frequently. I like having these on an early dungeon level, since low-level characters are easier for players to gamble with.

Experiment

• A solar laser trained on a stone plinth; pulling a chain activates the laser, cutting anything on the plinth in half. 
• A machine that spits out two shoddy copies of whatever is thrown in its hopper. 
• Jeff Rients's classic tiny door. 
• Anyone who passes under the gaze of the Mercury Idol turns to mist for the next 1d6 turns (as Gaseous Form). Nonliving material like equipment and armor are unaffected. 
• A pedestal that polymorphs anything placed upon it into a beautiful vase. If removed, the vase reverts to its original form after a day or if it shatters. The vase currently occupying the pedestal is a polymorphed green slime. 

Experiment rooms offer a feature of open-ended utility to mess around with. You are probably familiar with them from the Dungeon Checklist. 

Experiments simultaneously resist understanding yet invite interaction, putting them in the sweet spot of good dungeon set pieces. The act of engaging with one is itself rewarding, because once the players learn the rules of an experiment they get to exploit it. The risk is lost goods, unwanted mutilation, and the like, while the reward is a new way for the players to use the dungeon to their advantage. 

Experiments operate on two axes of challenge: the challenge of figuring out how to properly interact and the challenge of figuring out how to exploit. Most good experiments only have challenge along one of these axes—in other words, something that is difficult to figure out how to operate should have a pretty good payoff (the splicing vats from Gardens of Ynn are a good example: there’s a complicated multi-step process you essentially have to trial-and-error, but getting them to work can lead to some pretty major benefits with no downside), whereas something that has an open-ended but not immediately beneficial utility should be rather straightforward to operate. 

Alter Environment

• A valve that raises or lowers the water level throughout the dungeon. 
• Flipping the switch to the blue side opens all the blue doors and locks all the red, flipping it to the red side does the reverse. 
• Removing the skull from the center of the pentagram banishes the warding seals and spirit guardians but awakens the Hungering Darkness. 

Alter environment rooms offer means to change how the dungeon is navigated. This can mean any alteration to layout, doors, hazards, and so on. 

It is widely understood that good dungeon design involves both rooms where interacting with something in one influences something in another and that player actions can have an influence on the shape of the dungeon. Alter Environment rooms accomplish both of these imperatives.

The more area of the dungeon affected by an alter environment room, the more it becomes a central gimmick of the dungeon. If it's just a one-off thing where the lever in room x raises the gate in room y you're not communicating much of a theme, but if the players must repeatedly jump through the magic mirror to solve puzzles in the mirror-dimension version of the dungeon then it becomes a mirror-dimension dungeon in addition to whatever else you have going on. Good to keep that in mind. 

Exchange

• Pour a potion in the Purple Witch's cauldron and she'll ladle you a vialful of her brew, which has the effect of a random other potion.
• A giant copper-shelled snail eats copper pieces and excretes gemstones of comparable value.

Exchange rooms offer an opportunity for players to change their equipment, gear, or treasure in unique ways. 

Exchange rooms are particularly effective if you frequently use randomly generated treasure hordes, as they give the players an opportunity to offset the quirks of the dice in the event they end up with six scrolls of protection from lycanthropes or whatever. They also expand the toolset available to the players in dungeons, allowing for a selectively reliable way to trade unwanted inventory for something more useful providing new access to goods or services.

Side Quest

• A statue comes to life when it's missing hand, found elsewhere in the dungeon, is restored. 
• A vault's crystal door only opens once all the crystal braziers scattered throughout the dungeon level are lit. 

Side Quests offer a new goal in the dungeon and gives players players can pursue in addition to conventional dungeoneering activities.

Side quests work because they provide a little spice to dungeon exploration, giving a players a new avenue for progression. They also bring that much-coveted interconnectivity because, as you can guess, the object of the side quest must involve at least one other room.

Puzzle

• Giant statue of a long-dead emperor looking menacing on the far wall; on the statue's plinth an inscription reads "Salvation through submission." Doors lock, poison gas fills the room, in a low hidden niche in the plinth—clearly visible to anyone kneeling before the statue—is a small switch that deactivates the locks and gas.
• A room full of mirrors; one mirror reflects a door on the opposite wall that's not actually there. The mirror that reflects the door has a secret passage behind it. 
• Anything involving a riddle.

Puzzles offer an in-game scenario that directly challenges the players’ ingenuity (or ingénue-ity, but I have less experience with that). 

It should go without saying that everything in a dungeon can be a puzzle, like combat, traps, navigational hazards and so on, so special rooms are no exception. 

Puzzles can be contained within a single room, but they don’t have to be--a common tip for designing puzzles is to seed clues in other parts of the dungeon to promote interconnectivity. 

“But if a puzzle has clues seeded around the dungeon, what distinguishes it from a side quest?” the hypothetical gun aimed at my head says. “What’s the difference between moving room to room to collect macguffins vs. moving room to room to collect clues?”

 

The main difference is: Puzzles are about thinking and Side Quests are about doing. Imagine a treasure vault guarded by a demon who will only let the party through if they utter a specific passphrase. In a scenario where each word in the passphrase is found within a different room, and the sequence is rather easy to intuit, this challenge is a side quest—it’s pretty easy to figure out what the problem is and the challenge becomes finding each word. But in a scenario where the passphrase is the solution to a riddle, or encoded in a mural elsewhere on the level, you’ve got yourself a puzzle. Admittedly there can be a lot of overlap between the two, but my rule of thumb is if the more demanding a side quest is the less demanding the figuring-out parts should be, and vice versa. 

Minigame

• A pack of goblins invite you to race alchemically powered junk-karts. 
• The mind-cube imprisons you in a mental maze, resolved by solving an actual pen-and-paper maze. 

Minigames offer an in-game scenario resolved through novel game systems. 

Minigames make for good diversions and give players a break from the main game. I ran a session recently where the party got access to an exclusive gambling hall. We spent most of the evening playing through the dice games in Appendix F of the AD&D DMG. It was a lot of fun, but not the kind of thing anyone wants to do every session. 

Transit

• Room drops off to a massive void; lighting the candle on a nearby plinth attracts giant floating jellyfish that bring anyone who grabs ahold a harmless tentacle to a deeper dungeon level. 
• Two identical circular chambers, each with a lever on the floor and a single door, north end for one and south for the other; stepping in one chamber and pulling the lever appears to rotate the room, door and all, 180°, transferring everyone to the other chamber elsewhere in the dungeon.

Transit rooms offer novel means to navigate elsewhere in the dungeon beyond your typical hallway or staircase.

Transit rooms allows for alternate routes for navigating a dungeon, can help parties save time and cut down on backtracking on repeat dungeon ventures, and can serve as navigational challenges. 

Trick

• Illusory stairs conceal a spiked pit. 
• A statue of a stern-looking angel. Anyone that approaches within a few inches must save vs. paralysis or be grabbed and restrained by the statue, which proceeds to release a blaring alarm.
• A room lined with racks and racks of ornate swords; removing one causes the swords to animate and attack.

Trick rooms offer a nonstandard challenge or hazard. 

Tricks feel very old-school in the sense that many of the ones you see in classic modules feel deliberately designed to mess with the players in a kind of funhousy meta-gaming-from-the-DM-side way. That flavor of adversarial DMing has fallen by the wayside these days, as well as funhouse dungeons in general, but a thoughtful trick here or there can create a memorable moment and convey the more malevolent aspects of the mythic underworld. I might disagree with this claim later, but: a hallmark of a certain kind of old-school mindset to approach play is that having horrible things happen to your character can be as fun and engaging as having them succeed. 

Curiosity

• Room echoes with the voices of everyone ever slain in the dungeon. 
• An idiosyncratically cozy and well-appointed study, totally unlike the rest of the dungeon, complete with wizened sage reading & smoking a pipe in front of a warm hearth, somehow unmindful of the fact he's in the middle of a giant dungeon. 

Curiosity rooms offer a unique and distinctive location that lends to the dungeon’s mystery/majesty/dread.

Dungeons should have a healthy amount of idiosyncratic areas interspersed among standard rooms and corridors filled with traps, monsters, and treasure. Sometimes, these idiosyncratic locations may not have a clear utility or challenge or problem to solve. Curiosity rooms are less focused on the objects within than the locale itself; while they be focused around a distinctive set piece, like a unique NPC, the primary effect of a curiosity room is atmospheric.   

Art by Pedro Friedeberg