Gauging combat challenges

In the comments of a fairly recent post, I was asked to describe how I judge the challenge level of a combat encounter.  Short answer is that I don't have any hard-and-fast formula, and more or less eyeball it.  But of course that only evades the real question, which is what do I look at when eyeballing in order to make a judgment?

Firstly, let me say that encounter balance, as fetishized in some recent editions, is abhorrent to me.  Crafting every encounter to be "level appropriate" takes the fun out of the game, in my estimation.  I don't like railroady scenarios with scripted highs and lows that require easy victories over mooks and dramatic nail-biting climaxes.  And no encounter should be a mandatory combat - if the players can talk, bribe, sneak, or trick their way past something, the DM absolutely should not nullify that to force them into Exciting Combat!™

That said, I also don't want to create dungeons full of killer encounters or boring cake-walks.  An adventure should include plenty of opportunities for winnable combats, as well as encounters that demand more discretion.  Balance, to me, takes place at the level of the entire dungeon or scenario, not zoomed in to the individual encounter.

The amount of damage a group of creatures can do in a round is, I think, the most important consideration in judging their threat level.  Two primary factors contribute to this: the damage potential of each attack, and the total number of attacks per round of the group. 

I would weight the total number of attacks more heavily. A fight against four goblins is likely to be more deadly than a fight against a single ogre because the goblins get four chances to hit every round, while the ogre only gets one.  Against a party of 1st level characters, the goblins could potentially kill four in a round, while the ogre can't finish more than a single one at a time, no matter how much damage it rolls.

Damage per attack I would judged based on how many attacks it would take to kill a typical PC.  The more rounds the party can stand against it, the less dangerous it is to them.  Can it kill a PC with a single attack?  An attack that just hurts a character is a prompt to make a choice: withdraw or fight on.  This is an important consideration because character death, if it happens, is more likely to be seen as a result of player choice.  A one-hit kill is just a one-hit kill.  If you want to give a 1st-level party a fighting chance to engage in combat without too much anxiety, make sure to have some monsters that do 1d3 or 1d4 damage around.

Hit Dice are the usual unit of Monster Toughness in old school games.  Dungeon levels are supposed roughly to correspond to the average HD of the monsters found in them, and BECMI and Rules Cyclopedia D&D even have an encounter balancing formula which is based on Hit Dice.  However, Hit Dice are a distant third in my estimation of monster threat level.  What they are is a fairly good indication of how long a monster will last in combat, and thus how long it will get to keep making its attack and damage rolls against the PCs. 

Hit Dice also affect the chances of successfully attacking, but only by about 5% per HD, which is a lot less than extra attacks do.  A 1 HD creature needs to roll a 14 or better to hit AC 5, which translates to a 35% chance.  A second attack increases the odds of getting at least one hit to 57.75%, better than having 4 extra Hit Dice! 

Quite often, big HD correlate with big damage, but not always, so it's still a good idea to gauge them separately.

All else being equal, a single high HD monster with multiple attacks is usually more dangerous than a group of lesser creatures whose HD and attacks approximate it.  Consider a pack of five 1 HD orcs with 1d8-damage weapons and a 5 HD owlbear with three 1d8 attacks.  Each orc will take 5 or so points of damage to kill, and each one killed reduces their number of attacks by one.  The owlbear gets its three attacks per round until it's dead.

Armor Class rates a little bit lower than Hit Dice in my Monster Threat Assessment.  It too affects how long the monster remains alive and fighting, but unlike a big pile of hit points, which can only be whittled away, AC is bypassed by a good attack roll, and a d20 is a lot swingier than most dice you might roll for damage. 

Special attacks are trickier to assess.  For low-level parties, their effect is actually minimal.  A failed save vs. poison might kill you, but so will a single good solid physical blow, and dead is dead.  The odds of missing a save and getting hit in combat are only a little bit different.  A save-or-suck power is similar to a low damage attack: it's a cue to rethink one's position, not instant Game Over.

Save-or-die and save-or-incapacitated powers become a big deal at mid levels, not because they become more absolutely dangerous, but because they're now a lot more dangerous relative to attacks that do hp damage.  An orc with a sword and a medusa with a petrifying gaze can both take down a 1st level character in one round.  Only the medusa is likely to be able to do the same to a 4th or 8th level character.  The character's hp increases almost always greatly outstrip saving throw improvements, and while healing spells and potions are by now fairly common, spells that will reverse the effects of poison and petrification are still either out of reach or in short supply.

By high levels, saving throws have improved enough to make the success rate of save-or-die effects acceptably low, and the party probably has access to remedies, which makes them an inconvenience rather than a deadly peril.

Of course, the number of attacks principle also applies to special attacks.  If a monster can direct its special attack form against multiple targets at once, or there are several of the monsters in the encounter, it magnifies the threat level in much the same way.

Lots of attacks > big damage per attack > high HD > high AC

Combinations of those factors are possible, naturally.  So, lots of attacks + big damage per attack generally trumps big damage and high HD;  big damage and high HD beats high HD and high AC, etc.  What about lots of attacks and high AC vs. big damage and high HD?  How do special powers change things?  Use your own judgment.  It's an art; not a science.

Putting It In Play

In practice, I try to balance a dungeon as a whole, with a lot of encounters that I think the party could handle without too much trouble, some that would be quite risky, and a few that would almost certainly be disastrous if handled with straight-up combat. 

Remember that a good fight is one that costs the party some resources to win, not necessarily one in which the sides are evenly matched.  To a wise adventuring party, evenly matched battles are to be scrupulously avoided except in the most dire need or the richest possibility of reward.  Evenly matched means that both sides are likely to suffer losses, and either side could end up defeating the other.  That might sound exciting, and it is sometimes, but an adventure is more than one fight.  It's a war of attrition.

In a good dungeon, the PCs might be able to win any given fight, but they probably can't win them all, one after another, in a gauntlet match.  Even winnable fights must often be avoided, in order to conserve resources for fights that are not merely winnable, but important and/or profitable.  "Can we win this fight?" is an important question, but so is "What about the next one?"

1st level parties are the toughest to plan for because, with their low hit point totals, outcomes depend heavily on the very swingy d20 attack roll.  1st-level characters and 1 HD monsters can go from full strength to dead with a single attack.  A seemingly even battle can become lopsided very quickly if one side has a run of lucky or unlucky rolls.  Additionally, if the party includes a spell-caster, the outcome may hinge heavily on which spell he has ready and whether he still has it or has already used it. 

If you want to design a dungeon for low-level characters in which direct combat will play a big part, encounters should be predominantly with numbers of monsters smaller than the PC party, with 1 HD or less, low damage potential, and poor ACs.  A few encounters can be with even smaller numbers of creatures with 2-4 HD and better damage or AC.  Anything bigger, tougher, or more numerous is a serious risk -- but don't let that discourage you from including a couple such encounters.  It ain't all about chopping things up with swords, and part of the fun is knowing the difference.

As characters gain in levels and hit points, they generally survive longer, and overall, combat becomes less swingy.  The more rounds they can go without dying, the more rolls are made, and the more rolls made, the more the cumulative result is pulled toward the average.  Characters with a few levels under their belts can go toe-to-toe with monsters well above their weight class more successfully than low-level ones can because hit points increase a lot faster than damage potential. That doesn't necessarily mean they'll win, but an ill-chosen fight is less likely to wipe them out before they can even realize their mistake and run away. 

Still, I think it's good to follow the rule of thumb that the majority of encounters should be ones that the party could handily best in combat, but will take a bite out of their resources.  The more fights they pick, the more their resources and hit points get ground down, the closer they get to being that 1st-level party all over again, when life and death can hinge on a single misguided choice or bad roll of the dice... 

Ingredients of a micro-setting

Last post, I rambled about micro-settings in D&D: Pre-designed and stocked areas without any particular plot attached.

Making a micro-setting is both similar to and different from building either a standard adventure or a large-scale setting.  It requires the former's granularity of detail and the latter's focus on open-ended potential rather than specific events and actions.

Details which are important to the form are:

Maps: As the name implies, a micro-setting should be relatively small.  How small?  There's no objective limit, but I would say small enough that all points of interest can be explicitly marked on the map.  A macro-setting map, such as a hex map of a kingdom or a continent, only shows the most notable feature in each hex, such as a city or a type of terrain.  In reality, a six-mile hex can contain a lot of interesting stuff, far more than a single icon would indicate.  The hex map might show a village beside a river, but there might be a wizard's tower on a tiny island in the river, a monastery on a rocky crag overlooking the village, a ruined castle in the boggy area by the riverbank south of the village, and a cave where the local youths go for mischief which unknown to them contains a secret entrance to an ancient underground stronghold.  The micro-setting map should be of high enough resolution to show all those things and where they lie in relation to one another.

A base of operations: A complete micro-setting should include a place of relative safety, where the characters can rest between adventures, restock and upgrade equipment, store treasure, gather information, and recruit help.  It could be a fortress, an trading post, a village, a fleet of ships at anchor, a clan-steading of dwarves or elves, or even a lair of friendly monsters.  May be mapped and keyed, a la the Keep from B2.

People: Important, influential, and interesting NPCs, such as leaders and authority figures, mercenaries for hire, merchants and traders, professional services, rivals, mentors, and potential employers. Some bare-bones stats are a good idea; a few personality traits and motivations for each one are even better.

Factions: Organizations of people and monsters, whether formal or informal: guilds, families, tribes, houses, clubs, secret societies, religions, etc.  What are their interests and aims, and how do they relate to one another?

Dungeons: Dark and dangerous places to explore for fun and profit.  The setting should include at least one good-sized dungeon or several lesser ones, each fully mapped, stocked, and ready for play.  (Some published micro-settings make exceptions as a teaching tool for new DMs; the Cave of the Unknown in B2 is an example.  You'd still want to fully map and stock it if you intended to use it as part of the overall setting, though.)

Adventure hooks: Basically any fact about the setting that might lead to adventure opportunities.  Often presented in the form of a rumor list.  These may appeal to the party's sense of heroism or helpfulness (i.e. the needs and concerns of the common folk regarding things dark and dangerous) or to their curiosity or self-interest (rumors of treasure, magic, or just weird things.) 

Of course, what you don't write up in detail is nearly as important as what you do.  Anything that isn't directly relevant to running a game in that micro-setting should be left vague or unspecified, no matter how interesting it might seem.  This allows the micro-setting to be easily inserted into someone's game world, or for you to re-use it at some later date in a different game world without having to gut it to avoid conflicts.  It truly is a "module," plug-and-play.

Focus on the Right Here and Right Now.  No extensive history, no intricate connections to the wider world.  We don't know why the Keep is on the Borderlands, except that it's an outpost of Law that stands between civilization and the forces of Chaos.  We don't know how long it's been there or who built it.  We don't know where the castellan came from or how he was appointed to this post.  Leaving all these spaces blank makes a micro-setting flexible and versatile.  According to the needs of the particular campaign and world, the Keep could be new or old.  It could be pushing back the frontiers of civiliation into the wild, or the last bastion of a retreat.  The castellan could be a humble enlisted man who won his position through grit and determination, or the bastard son of a powerful noble shunted aside with this remote posting.

It's a setting, not a story.  When you're populating your micro-setting with people and creatures, think about motives and goals, not actions.  Actions come later, when the campaign is in motion.  Instead of writing up what a monster or a faction will do, figure out what it wants in the long run.  A typical plotted adventure might have the evil cult kidnap the local ruler.  In a micro-setting, the cult might wish to quietly infiltrate and corrupt the local good church, entice new members to join, and ultimately establish itself as the most powerful organization in the setting.  Broad objectives like this allow the DM a lot of freedom to decide just what methods and tactics the cult will use, and adapt to changing circumstances and opportunities.  If and when it makes sense for it to kidnap the ruler, it will do so.  A lot depends on the actions of the players - they are the wild cards in the game, after all, and their decisions can simultaneously close some opportunities for the other forces in the world, and open others.

I think that wraps up this particular topic.  Next up, thoughts on making adventures in a "plotless" setting or micro-setting meaningful (i.e. plotting on the fly during the campaign.)

Unlocking challenges by spending loot

A lot has been written on how to lighten the coffers of experienced PCs.  If you go by the book, and award XP for gp on a 1:1 basis, the typical fighter character will have amassed a fortune approaching 200,000 gp by 9th level, even allowing a fair chunk from defeating monsters and other awards.  Pool an entire party's resources, and you could be looking at more than a million gp. And once the last fighter PC has bought his plate armor, probably before he even reaches 2nd level, there's not a whole lot on which to spend the loot, at least until you hit Name level and contemplate building a stronghold.

Suggestions range from unforgiveably heavy-handed (theft, surprise taxes) to transparent railroading (training costs and such.)  Then there are some intriguing ideas, like carousing rules, which award XP only for treasure spent on carousing between adventures.  One variant I've seen (and I can't remember where, so if it's yours, step up and claim credit!) adds other options for characters who are more studious or civic-minded to gain XP by spending their gold on research or charity.  Though I personally don't think I'd use it in my games, I can see the advantages it has over the other methods in terms of player agency:  Players have an actual choice, to spend their hard-won loot on carousing or some other form of reputation-building activity, in effect dissipating the loot for XP, or they can save it and spend it on more practical things that aid their careers in more tangible ways.

I'm thinking of something a bit different, though.  It wouldn't have to conflict with the spend-money-to-earn-XP paradigm (in fact, it would blend pretty nicely with it.)  In classic console-based RPGs like Final Fantasy and (my personal favorite) the Dragon Warrior series, the heroes don't have access to the entire game world all at once.  They must earn access to new places and win the favor of important people in order to advance.  New areas and quests are unlocked as the heroes progress in the game.  Rescue the merchant's daughter from a monster attack, and he rewards you with a ship so you can sail to new lands.  Recover a magical key from a remote town so you can open all the doors in the castle.  Gather enough gold so the old man can hire workers and realize his dream of building a tunnel under the mountains to the next kingdom.

The analogy of console RPG to D&D isn't perfect.  The money gathered in most classic CRPGs is spent almost exclusively on weapon and armor upgrades, of which there aren't a lot in D&D.  The unlocking of new areas to explore and new quests to fulfill is driven mostly by acquisition of "plot coupon" items or defeating boss enemies in previous quests, and is usually pretty linear in nature.  Still, the general principle of unlocking new challenges translates quite well to a tabletop RPG sandbox.

The idea of the sandbox, of course, is that the PCs can go anywhere.  That doesn't mean everything has to be free and easy, though.  All sorts of barriers exist to hinder characters going wherever they want to go - barriers physical, magical, political, and social.  Money can buy passage in many different ways.  What's different about the sandbox as opposed to the CRPG is that where the CRPG has a fairly linear plot, the sandbox offers many paths, none of which is mandatory.  The characters don't HAVE to spend their hard-earned gold on any one of them if they don't want to.  Players can choose which opportunities to pursue and which not, and that makes their decision to spend gold on pursuing them meaningful. 

The DM's job is to seed the campaign with enough rumors and facts about these difficult-to-reach places that the players are dying to get to them.  Put the ideas in the players' heads early, long before they have the resources to actually go there, and remind them often enough to keep their imaginations churning.  Make sure you keep track of what you've told them, but there's no need to develop anything in great detail until they're on the cusp of actually doing it.  Sketches and hints are enough for now.  Tell them how the sailors talk with superstitious reverence of the Phantom Isle rumored to be the last, cursed stronghold of an ancient race.  Toss out rumors of the Lost Temple of Bara or the abandoned city of the dwarves.  Show the benefits that more experienced champions earn through their connections with powerful guilds and nobles.  Have a half-mad caravan guard come stumbling home, the last survivor of an ill-fated expendition to the exotic lands beyond the mountains, raving about cities of gold and jewels.

In the meantime, keep them occupied with the usual low-hanging fruit of beginning adventures - local ruins, orc raids, the abandoned mine where people hear that mysterious knocking sound at night.  These need not be boring or mundane adventures, but the gleam of what's just over the horizon should lure the party ever onward and have them counting their coppers after every new haul to see if they've got enough to bankroll the Big Quest.

How do you get them to drop coin on these things?

• The most prosaic example is the island.  Booking passage to coastal towns a simple matter.  Getting a captain to drop you on an ordinary island slightly off his usual route might cost a bit more.  Talk about an expedition to some dreaded place, and you might have to buy a ship outright and hire a crew of the craziest and most desperate souls you can find.
• The doorway into the lost temple is sealed, and the walls around it covered in inscriptions in a long-forgotten tongue explaining how to gain entrance.  It's going to take a sage a few months and a big budget for old books to decipher it.  Maybe the party even needs to take him on the dangerous journey to the place itself.
• The cave that once housed the nefarious gang of thieves is covered by a landslide.  It'll take a party of adventurers months to clear it, unless they shell out some coin to hire laborers and keep them safe while they work.
• There's a wilderness area, rife with many ruins and dungeons to explore, but far from any town or other safe haven.  The adventurers might need to construct a secure base, perhaps a pallisade fort, and garrison it with mercenaries so they have somewhere to come back and rest between delves.  Otherwise, constant threat of wandering enemies will take its toll.
• Connections to the Merchants' Guild, the local nobility or royalty, or a secret society might bring lots of special commissions, but in order to cultivate those connections, you're going to need to grease the wheels and dress the part.  Showing up at the Duke's Ball in full murderhobo attire is not likely to end well, let alone impress the Duke into taking the PCs into his confidence.  The PCs may have to spend a lot of time and money cultivating their image, purchasing a villa or manor in which to live large and host social events of their own, before they're even invited to the Duke's events.
• On the other hand, sometimes the best friends to have are from low places.  To win the trust and admiration of the peasantry, the PCs can spend their gold on temples, houses of healing, roads and bridges, fortifications against marauders, or whatever the locals most need.  Especially worthwhile if one of their goals is to overthrow or otherwise undermine the authority of a local despot.
• The dwarven ruins were sealed so long ago that even the dwarves have forgotten why they were abandoned, but none is daring enough to return, despite persistent rumors of hoards of mighty weapons and armor and the forgotten secrets of their forging.  In order to open the seal, a series of three keys must be made, with precious metals and stones, by the most skilled dwarven craftsmen, and they're not going to do it for free.
• Or, perhaps the current dwarf stronghold guards the only pass through the mountains to the mysterious kingdoms beyond, and the dwarves are xenophobic and suspicious of humans.  The party could spend months doing favors to win their trust...or offer them a tribute of gold and jewels to gain their favor and passage through the mountains.
• In the depths of some dungeon or ruin, the party stumbles upon a magical portal.  Unfortunately, it's broken, and will take a lot of resources and the assistance of NPC experts to repair.  Tantalizing rumors abound as to what lies at the other end. 
• The PCs find a map to the location of a sunken ship or island, and need to have a high-level magic-user cast enough Water Breathing spells for the whole party.  She's going to need a good incentive to leave her own research and go on a sea voyage, or even just write up a supply of scrolls of the spell.  She doesn't accept IOUs or payment on contingency, but cold hard coin will do just fine.

The range of possible expeditions is limited only by imagination.  This isn't meant to be an advancement tax; the players should always have a choice not only between various quests on which to expend their money, but whether to take up any of the costly expeditions at all.  Players can keep on scouring the easily accessible areas if they're determined to pinch coppers, but should be aware that the best loot and the most amazing discoveries haven't remained undiscovered by being easy to find and break into.  As they say, you've got to spend money to make money (or magic, or discoveries of lost civilizations or earth-shattering knowledge of the campaign world's secrets, as the case may be.)  Creative ways of reducing or avoiding monetary costs should of course be openly entertained by the DM, but sometimes spending money is just the best and most efficient way to go.  If the PCs would rather bribe the dwarf king than perform a series of Fed-Ex quests for him, don't discourage them.

Of course, there really should be something awesome awaiting the PCs when they finally reach their long-dreamed-about destination.  It need not be what they were expecting, or even what they were told to expect by madman or by sage, but it had better be good enough that they'll be excited about unlocking the next inaccessible place too. 

Utility spells and adventure design

I was poring over the spell list in the Moldvay Basic rules, pondering a few posts, maybe a series, on under-utilized spells.  Perusing the description of the humble 1st level magic-user spell read languages, a thought struck me about the style of gaming for which those spells were originally designed. 

So, when would a player choose to prepare or cast read languages?  The obvious answer, of course, is when the DM is running the type of game in which the player stands to gain something by doing so.  I think that type of game is either a true sandbox or one with a predominance of sandboxy elements.

Consider first a fairly linear, plot-driven adventure.  Because the adventure setting and other details are probably going to be used only once, anything extraneous to the plot is likely to be pretty thin, when present at all.  Writing up descriptions for locations, dungeon rooms, NPCs, etc. that aren't related to the plot is just extra work for the sake of work.  The dungeon won't have many rooms that don't contain something important to the adventure.  Major obstacles are usually essential to the plot, choke points that must be surmounted in some prescribed fashion in order to proceed.  If there's a door marked with ancient runes or a scroll with an encoded message, it's never superfluous or tangential to the plot.  It's there to advance the PC party toward the final resolution of the quest.

For that reason, it's pretty rare that the author of such an adventure would include those things without also including the means for deciphering them.  The adventure must not hinge on the players having access to a particular spell at a particular point.  It must not come to a grinding halt, or even end in failure, for want of a magic-user who knows and has prepared read languages.  Instead, the author will generally drop in some sort of plot coupon - a Rosetta stone, a mislaid copy of the cipher, an NPC who knows the ancient language, or (completely lacking imagination) a scroll containing the spell in a chest nearby.

Savvy players will pick up on this, and realize that it's mostly pointless to prepare or cast read languages.  Search for the plot coupon, and save those precious spell slots for slinging magic missile and sleep spells during the inevitable climactic set piece battle.  It is possible, of course, that the price of winning the plot coupon is greater than a first-level spell, and it would make sense to circumvent it with a quick casting of read laguages.  Given the tendency of that type of adventure toward railroading so that No Encounter is Wasted, though, it's likely that the author will contrive some reason that read languages won't work, requiring the party to go through the encounters to get the plot coupon.  (If you really want to discourage players from preparing utility spells, make those spells useless in any situation that significantly advances the party's goals because it interferes with somebody's conception of a good story.)

Compare that to a sandbox campaign, in which a large dungeon complex or wilderness area may be the scene of multiple adventures, whether they're simple dungeon crawls ("Why?  Because it's there!") or quests to accomplish some particular goal.  There are multiple paths by which any given location may be reached, and many features that aren't essential to any plot.  They're just there to be discovered and utilized in whatever ways the players can conceive. 

In this sort of environment, players have no assurance of plot coupons to get them past obstacles without expending resources, nor do they automatically know which things they encounter are relevant to their current quest and which aren't.  If they want to read the message on that door, engraved in strange glyphs of the forgotten tongue of the Old Empire, they can search the dungeon high and low for some secret decoder ring that may or may not exist, they can make a rubbing of it and take it to a sage in town, or the party magic-user can zap it with read languages and find the answer right away, without further waste of precious time.  They can also choose to move on and forget about it.  The most important consideration is that the success or failure of the adventure doesn't hinge on their reading the message.  It's not a choke point which must be passed to advance to the next stage; it's one piece of a puzzle, and the players might still be able to make out the overall picture without any given piece.  Because the possibilities are so wide-open, there's no need to ensure that the party can read it even if they don't have a spell, and no reason to prevent the spell from working to preserve anyone's idea of how the story should progress.

Reading the message might allow the party to claim any number of advantages.  Perhaps it forewarns them of hazards, or gives access to a shortcut that bypasses those hazards.  Maybe it points to a magic sword or a potion that could be of use in this or future adventures.  Maybe it's a map of part of the dungeon, or a misdirected message that discloses parts of the villain's plans that a clever party can exploit.  Maybe there's a hook for a future adventure.  Maybe there's bonus loot to be gained.  Maybe there's something unrelated to the current mission that reveals interesting information about the dungeon or other features of the campaign setting.  Or maybe it leads to a monster or trap that deplete their resources.  There's risk involved, after all.

Of course, all of this is moot if you don't liberally salt your setting with books, scrolls, engravings, heiroglyphs, ciphers, and other written material and make at least a fair bit of it helpful and relevant to the party.  

Light and sound in the dungeon

Lights and sounds in the dungeon - and I'm talking about the ones present in the environment, not emitted by the adventuring party - have always tended to trip me up when I'm running a dungeon crawl.  Monsters, traps, and other features are either represented on the map itself, or noted in the dungeon key, or both.  Most of them tend to stay where they're placed, so until the party actually enters the room they're in, you don't need to worry too much about what they're doing.  There are exceptions, of course.  If the goblins from area 3 will rush to the aid of those in area 1 if the alarm is sounded, that's usually noted in the area 1 description, where it's most relevant.

Not so with sources of noise.  Sure, it's easy enough to sort out when a character listens at the door of a room.  You just go to the key for that room, take note of what's there, and decide what, if anything, the character can hear.  But what do you do when someone listens down an unkeyed corridor, or when there's something out there making enough noise that the party should be able to hear it without having to declare that they're listening?  I'm talking about stuff like waterfalls, rushing streams, big clanking machines of unknown purpose, a forge in use, gnomes mining, and drunken goblin jamborees.  Players should hear those things long before they enter the exact room where the noise originates, or one adjacent to it, but it's either a lot of tedious looking-up or a lot of extra mental balls to juggle in order to keep them apprised.

The same may be true to a lesser extent with light sources, if there are any in the dungeon and they aren't all hidden away behind closed doors.

Come to think of it, smells and tactile sensations such as heat and cold kind of fall into the same category.  

How to handle this on a dungeon map and key, though?  Map symbols seem like an obvious possibility, but I'm not sure it's the best one.  Symbols might tend to blend in too much to the rest of the map, necessitating long interruptions while the DM scans the map.  They might also be mistaken for physical features of the dungeon. 

My favorite idea is to use map symbols, but mark them on the map with colored highlighter pens.  Maybe a gold circle for lights, green "stink lines" for strong smells, red or blue wavy lines for heat or cold, and a bell shape (color not important) for sounds, with a number written inside it to signify the relative volume of the sound.  (1 for low volume, audible only from short range, like a gentle stream or a quiet conversation.  2 for things roughly the volume of an ordinary conversation between two to four people.  3 for louder noises, like a large gathering or a blacksmith's shop.  4 for really deafening stuff, like a large waterfall or a dragon roaring.  Intensity numbers may be added to the other features too, if desired.)

Having the symbols in color like this would make them stand out, and a DM could estimate at a glance what lights, noises, smells, and other sensations the party could perceive from any position, and quickly flip to the relevant location in the dungeon key for more information.

The drawback is that this would be a difficult system to use for published adventures.  Perhaps grey (as opposed to black) versions of the symbols could be printed on the map, with instructions to the DM to highlight them during pre-game prep.

If anyone has another system for handling this sort of thing, feel free to describe it and/or post a link.