The Physical Environment (CSC)

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Now that we have examined a number of factors which can contribute to making a dungeon exploration game mysterious and memorable, lets look at the physical hazards which a party of adventurers is likely to encounter beneath the surface of the earth. Although each of these could be incorporated into every single dungeon adventure which you referee, it's probably better to hold off on them and use each one only when it's appropriate for the plot or setting. For example, if you have decided that portions of your Haunted Mine are going to be filled with explosive gas, then there's no need to also have it subject to violent geological tremors and earthquakes. Save the other unusual features for a game in which they are better suited to the environment.
==Cave-Ins==
Perhaps the most familiar of all the hazards which characters are likely to encounter as they explore the depths of the earth, cave-ins can be very dangerous. In most regions of the average dungeon, cave-ins will be rare. This is due primarily to the fact that older subterranean structures of a natural origin tend be fairly stable. Those that are not collapse early on in their development and are, thus, not usually around long enough to turn into dungeons.
Man made structures, on the other hand, are more dependent on regular safety checks and upkeep. Without such close attention, they can quickly become unsafe to travel in.
If the referee decides that an area is generally safe to travel in, consideration must be given to the possible actions of the party. For example, a length of an abandoned dwarvish mine might normally be fairly rugged, but how will it stand up to a wizard's chain lightning spell?
Of course, cave-ins can also be engineered by adventurers or dungeon denizens as a means of attack. This can be direct (dropping the roof on the victims) or indirect (dropping it behind them to cut off escape routes), depending upon the goals of the ambushing party. Such traps must be rigged with great care, however, as there is always the chance that an artificial cave-in may get out of hand and bring down whole sections of the complex, possibly even killing those who set up the trap.
==Darkness==
By the far the most common and easily countered hazard in the typical dungeon is simply that fact that it's pretty dark down there. Most referees don't go out of their way to remind players of this fact, and it's generally ignored in the average game. But let's take a moment to consider how we can use this dreadful darkness to our advantage in brightening up our adventures.
The first thing to consider is simply this; we know it's dark in a dungeon, and that's why characters will have torches or lanterns with them. A very wise thing to do, of course, but there are inherent problems with torches, lanterns, and other forms of light. The most obvious of these is the fact that light in a dungeon draws attention the way it draws moths in the wilderness. There is no better way to advertise your presence to the inhabitants of a subterranean realm than by casting bright light about for all to see. And make no mistake, while the light may only provide you with good vision for a few yards, it can be seen at much greater distances. Tb a great many monsters, a light in the distance is like a beacon that says "free food - all you can eat - come and get it".
A good way to remind characters of just how dark it really is in a dungeon is to extinguish their lights every so often. This can be done with a cloud of steam from a geothermal hot spring or a gust of wind racing along the corridor from some mysterious region up ahead. As often as not, in fact, it can be accomplished with a simple darkness spell cast by some magic using monster.
==Flooding==
Many underground chambers, especially those created by water, like sea caves or limestone caverns, often have standing water in them. In some cases, it may be only a trickle or a stream while in others it may be a raging river. hi addition, the level of water in a cave can change with the passing of time. Sea caves, for example, may be regularly flooded by the rising tide while the river running through a limestone cavern may overflow its banks every spring with the thawing of a near by glacier. Perhaps the most dangerous aspect of dungeon flooding is simply the fact that there is no way to escape the water. In such a confined space, every alcove and hiding place will be filled by the rising tides. Characters unfortunate enough to be caught in such a hazardous situation may find themselves fighting for their lives against the merciless elements.
==Oxygen==
As everyone knows, the vast majority of living creatures require oxygen to survive. Sadly, the dungeon environment is often lacking in this very element. As such, travel into regions in which there is little or no oxygen available can be quickly fatal to the average team of adventurers.
Of course, not all regions of an underground complex will be in this condition. In fact, the vast majority of underground realms are ventilated enough to allow air for respiration as long as unusual circumstances (such as a fire) do not deplete it in a rapid manner.
Dungeon Masters should use oxygen starvation carefully, as it requires that the party be in a region with no access to fresh air. Since they have almost certainly gotten into the area by walking, there is obviously an open passage to the surface which will allow some air flow.
In order for the lack of oxygen in an area to become life threatening, this connection with the surface world must be severed. This can be done with a cave-in or similar physical barrier which actually blocks off the air supply. If this does not fit in well with the plot of the game, the referee may wish to introduce a raging fire or magical spell to deplete the oxygen in an area. In fact, it may not even be necessary to use such drastic means to place the characters in a low oxygen environment. If an area is poorly ventilated, the rapid exertion of a combat with some monster may force their bodies to attempt to metabolize more oxygen than is available.
==Fires==
In most natural dungeon complexes there are few, if any, sources of combustible materials and, thus, fire is not very probable. In the majority of man made dungeons, however, there are often wooden supports and similar items which can ignite, hi fact, the danger of combustion in a coal mine is one hazard that must be carefully considered before entering into such a region.
The greatest danger presented by fires in a dungeon is not the flame itself, but the fact that it rapidly consumes oxygen. The larger the fire, the faster it burns off the oxygen, and the more dangerous it is to adventurers. Of course, when the oxygen is gone, the fire will be extinguished.
Another dangerous by-product of an underground fire is the smoke that it can create. In areas of poor ventilation it can quickly fill entire chambers. Because of its heavy carbon dioxide content, smoke can be just as deadly as any poison gas unleashed by an enemy.
==Noxious Gases==
Many subterranean regions, especially man made complexes like sewers, are filled with noxious gases. While these are not actually deadly, they can be quite overpowering and make breathing difficult and distasteful to adventurers.
Dungeon masters can introduce noxious vapors from a wide variety of sources. Rotting garbage, for example, can produce a stench which is so overpowering to the average human as to induce gagging or even vomiting. The stinking cloud spell is another classic example of this type of gas, this can be introduced by the characters to battle their foes or even released by a party of monsters lead by a spell caster. A third fine example of a source of noxious vapors is the troglodyte lair. As these vile creatures often secrete a very offensive smelling oil, the caverns which they dwell in is apt to be thick with its scent. A modern example of noxious vapors would be tear gas.
==Toxic Gases==
Far more dangerous than their noxious cousins, toxic gases are able to cause injury and harm to those who breathe them. In many cases, toxic gases will carry a distinct odor which may allow characters to detect them before they reach dangerous concentrations. In other instances, however, they may be utterly odorless and colorless. In the latter case, the party may be overcome by the fumes before they are able to react to them. Of course, the most common means of detecting odorless toxic gases is with the aid of a small songbird in a cage. As these fragile creatures are far more sensitive to toxic gases than humans or demihumans, they can act as early warning devices. In short, if the bird dies, get out of the area quickly!
==Explosive Gases==
Even more dangerous, perhaps, than toxic gases, explosive ones can lurk undetected until a party of adventurers wanders in with an open flame. Once ignited, they release vast amounts of heat, light, and energy in a sudden violent chemical reaction—that is, they explode.
To make matters worse, many explosive gases are toxic or noxious, compounding the danger of encountering them. In regions where coal or oil is common, explorers are prone to encounter pockets of methane (natural gas) which is toxic, explosive, odorless, and colorless. A more lethal combination would be hard to image!
Referees should use all forms of gases (toxic, noxious, and explosive) sparingly. If they are too frequently encountered, players will no longer be shocked by their effects. Remember, the most important thing in any game is excitement and entertainment, both of which are diminished if gimmicks are overused or predictable.
==Low Temperature==
Many dungeons are prone to being both cold, because they are shielded from the sun's rays, and damp, because they have vast quantities of water in them. Although this condition may not immediately become an obvious threat to the lives of the characters, it can make them quite uncomfortable and, if left uncountered, can prove fatal.
The rivers and streams found underground are notoriously cold, often just warm enough to avoid freezing, and can quickly disable anyone forced to spend time in them due to hypothermia (a dangerous reduction in body temperature).
The dungeon master can use the exceptionally cold waters of the typical dungeon setting to great advantage by forcing characters to pass through deep streams or punt their way across a wide lake, all the while struggling to avoid the ill effects of immersion in cold water. In many cases, numerous water crossings may be required to reach a party's objective, each of which presents fresh hazards to the already chilly explorers.
Attempts to counter the cold, by warming oneself before a camp fire or the like are all well and good, but have the disadvantages of creating a light (thus announcing your presence to everything in the area) and using oxygen to feed the fire (thus making your own breathing supply more limited). The players will have to weigh the risks and benefits of this course on their own.
==High Temperature==
On the other end of the spectrum, there are subterranean realms in which cold air and water are not likely to become problems. One seldom catches a chill, for example, from attempting to wade through a pool of water which has been heated to near boiling temperatures by geothermal activity. On the other hand, anyone in such a situation is certain to be badly burned.
Geothermal heat is found in many forms. Most commonly it manifests itself in hot springs and geysers of steam. In more exotic locales, it may be found in the form of a stream of molten lava or a boiling lake of magma. In the latter brimstone, a noxious (or even toxic) vapor.
Dungeon masters can use geothermal heat sources in much the same way that they use pools of bone-chilling water. A party may have to find some way around a stream of bubbling lava or through a plume of superheated steam in order to reach the climax of the adventure.
==Line of Sight==
Because of the twisting nature of the passages which make up many dungeon complexes, it is often easy to lose sight of other party members. In fact, it is easy to lose sight of almost everything. Remember that there is usually no light beyond that which you have brought with you and the area just around the next corner is shrouded in absolute darkness.
The inability to keep sight of party members who leave the main group makes the job of scouting very dangerous. As soon as you are out of sight, you're on your own. With luck, you'll be able to call for help if something attacks you, but you can never be sure.
A skillful dungeon master can use this factor the same way many television shows use actors without speaking parts. For example, Johndar the Thief is sent ahead of the part to watch for traps and act as a scout. Because he is elvish, the players decide that his infravision will be useful once he is far enough ahead of the party to avoid the glare of their torches and lanterns. Sadly, Johndar is cut down by a volley of arrows from a hidden grotto full of kobolds. A few seconds later, the party catches up with the dead scout. Just as the kobolds release a second volley, one of the players looks around and says "something's happened to our scout!"—Famous last words.
==Loadstone==
Some areas of the underground may hold deposits of magnetic ore known as loadstone. Although such areas are normally safe to travel through, large outcroppings of such ore can be dangerous. The mining of loadstone, however, can be very profitable and will often cause numerous mines to spring up in areas where it is discovered.
The most common use of magnetic ores in a dungeon setting is as a hindrance to mappers. In games which allow characters to purchase or acquire magnetic compasses, even a small deposit of loadstone will be enough to cause dungeon delvers to produce very confused and often wholly incorrect maps. As a rule, such occurrences are more of an annoyance than a physical hazard.
In extreme cases, dungeon masters may decide to place a large quantity of very powerful loadstone in a dungeon. The most obvious effect of this is that its magnetic field is so strong that it can immobilize characters in metal armor or with metal weapons. Any alloy which is subject to magnetic attraction may be yanked from the adventurer's grasp and pinned to the surface of the deposit. Encounters with loadstone veins of such intensity should be very rare indeed.