Our cave encounters are done but we’re not in the clear yet! Running the connective moments and making full use of the environment is just as important for a cave adventure as the encounters themselves. Every terrain is unique and should have its own challenges and atmosphere. Caves, in particular, allow us to inject claustrophobia and confusion into our adventures. The isolation challenges players in ways that no other environment can. This is where we’d like to help, by explaining how to use these factors in the descriptions and mechanics of your own game without overburdening your planning.
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A shape flies through the corner of the leader’s vision. She raises a hand, signaling those behind her to hold still. Seconds tick by. The unease in their stomachs grows as the silence continues. Hands creep to the handles of weapons and to draw spell components. Then, movement. Swords, arrows, and crackling sparks of energy all swing to aim at the approaching sound. From the boundaries of the shadow a small, bat-like creature scurries forth. It stops in place and turns up to them, wide eyes questioning the tense adventurers. The group sighs and chuckles, returning their weapons. Their resident mage, relaxing, casts forth a series of glowing orbs. They float in the air around the creature, illuminating the face of its much larger parent several feet behind.
1d20 Cave Encounters
This guide should help you run our 20 custom cave encounters. Each and every one is written with a new way to approach the environment and the options it gives you, with detailed explanations and ways of adjusting them for your own games.
Encounters by Environment: Caves
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Part of a Larger World
Caves are unlike deserts, jungles, and other environments. They tend to act as a feature within another region rather than being one themself, but can also function as the entrance to an entire network below the surface. This can create difficulties in planning their connection to the world, as you want to balance their realistic integration with a sense of isolation for the players. Ultimately, we can boil it down to a consideration of the cave’s location and contents. Use these as starting points, keeping in mind the purpose your caves serve in your campaign.
When placing a cave entrance, you want it to feel like a feature of the environment around it. The transition between the surface world into the underground is usually a quick one but is important for connecting the two. When viewed from a distance, describe it to your players as a piece of the surrounding area. Have your descriptions make note of the characteristics of the terrain that continue into the cave, such as vines or snow cover. These can reduce in density as your cave environment takes over. Typical features like stalagmites and stalactites, as well as the darkness of the cave, will replace them.
This all seems simple but is an important step for introducing your cave adventure. You want the entrance to feel like a natural progression, while also quietly warning players of what they are facing. Include hints of what challenges you intend to include. If the cave presents an immediate danger, you can emphasize features such as jagged stones and harsh angles. For deeper cave systems or introductions to longer cave adventures, you can focus on the cave stretching into darkness and out of sight. These are not as direct as the hints we use for jungles and other environments but serve the same purpose. Our goal is to subtly suggest to players that they need to be prepared for the isolation that we will cover later.
Connections to the Surface
The next step is defining the purpose and use of the cave. Think about the opportunities that the cave provides to both the creatures and people nearby. This runs parallel to planning the cave’s location, as the two will often form the in-world reason for the encounter or adventure.
The most obvious example of this is in monster lairs. Whether for wolves, kobolds, dragons, or even just people, caves represent a defensible position for creatures of all kinds to make their home. In this case, the cave will change to fit the creature. They will outfit it for their own needs, depending on their own intelligence and the length of time they have been there. This should be evident within the cave, but also in the surrounding terrain. Think about the creatures themselves and the impact they would have, whether that be resource gathering or evidence left behind from hunts. Their sphere of influence has the dual purpose of informing wary players while further emphasizing a connection to the world.
Many creatures will also use this theme in reverse. Spiders, bandits, and other predators are able to use the safety of caves as a lure for prey, with traps set to catch them. In these cases, they will often seek to remove any visual indicators of their presence and make the cave appear uninhabited. This is a good way to incorporate other random encounters but relies on you also including regular, safe caves. If every cave is a lair or trap, players will simply avoid them.
On the other end of the spectrum, caves are also a resource for towns and regular people. Mines are the most common use, with caves doing the work of exposing the presence of minerals or providing paths to where they can be found. They can also serve as tunnels for transport under difficult terrain, as well as the aforementioned shelter. In all of these cases, the importance of the caves will lead to people reinforcing their structure and ensuring their safety. They will much more closely reflect the town, often to the extent of appearing more like a building than a natural feature. This can, of course, vary depending on the proximity to the town and the effort invested in it. A derelict tunnel or unstable mine shafts are good ways of displaying the character of those responsible for their upkeep.
A World unto Itself
Caves function well as locations for a single, defined encounter. But there is another option that is significantly more involved and open-ended, while also giving more freedom. Tunnels and caverns can be used to create an entire underground world, complete with different biomes, terrains, and settlements. This allows you to set entire adventures (or even campaigns) beneath the surface. But it comes with considerations that need to be made.
Caverns and Tunnels
Essentially, the way to do this is by approaching it exactly as we labeled; as another world, underground. This means planning the caves as you would for an overworld map, in terms of settlements and roads in the form of larger, safer tunnels. The same can be said for changes in terrain. The underground will function as a parallel world, with specific differences to the world above.
One of these differences is when players leave the main tunnels and caverns. These deviations separate the party from the world, like overgrown forests and swamps and barren deserts do. Caves emphasize this further. They will quickly grow more wild, inhospitable, and unpredictable the further they are from civilization. Darkness, physical walls and obstacles, and changes in elevation will work to isolate the party from any help or escape, both mentally and literally. The effects of this will be most apparent as the players travel and during encounters.
When mapping your caves, do not try and include every single, little tunnel. Focus on the settlements, any wide, open caverns, and the main roads that connect them. Cover the smaller tunnels of encounters or travel in your descriptions, with general directions if players have a particular heading or are maintaining a map. This saves you obvious planning time while also giving you more room in-session to improvise and make changes when you need to.
Also like the regular world, your caves should have variations within them. This means having the details of the environment change throughout your cave adventure, making use of the different features like bodies of water, plants, chasms, and even pockets of magma. We will cover this in more detail as it pertains to travel and encounters a little later, but it should be a consideration in planning. Many of these features are large, obvious, and impactful, so they will rarely appear randomly. Think about them more like regions or biomes in the overworld and plan them with the necessary space and transitions.
The Underground Population
As always, the unique features of the environment should have an effect on its people and vice versa. Subterranean settlements and worlds will, again, act similarly to their surface counterparts, with certain features exaggerated. This is good. It means that much of your planning is the same, with only a few necessary details to set your cave adventure apart.
The first step is to ask yourself a question: how isolated is your underground world from the surface? The level of seclusion will determine basic factors such as available resources and the kinds of people that will be present. It is also an important part of worldbuilding and should be visible to players, even having a direct impact on them.
Let’s have a look at two examples on opposite ends of the spectrum…
A dwarven city with a good relationship with the surface has access to easy trade and assistance. They are able to set up supply lines to bring in resources such as wood and overworld food, depending on the environments and surface settlements nearby. This will be apparent in their architecture, as well as the fruitfulness of trade, courier, and escort businesses. The races in the city will quickly diversify and visitors such as researchers and tourists will be more plentiful. The city can call on outside help with any dangers within surrounding tunnels, though they may see less need to as they rely less on local industry. Ultimately, the city will more closely resemble a regular surface city, with a change of scenery.
Conversely, a city that isolates itself must act self-sufficiently. The people and companies will form around the industries available to them, many of which rely on finite resources of the environment. This, along with a growing population as people don’t leave for the surface, will require them to expand through the connecting tunnels. They will, therefore, need to maintain control of the area from any dangerous creatures to secure land and maintain safe roads. The advantage of this is a greater understanding of their location and ability to deal with these threats. The people themselves will be almost entirely native races, particularly those with darkvision, tending to be more insular and either less accepting of outsiders.
You can see how these examples both stem from the same question to form very different experiences for players. Building from a single point is a good way to realize details you might have otherwise missed. For instance, a town consisting only of races with darkvision and not expecting visitors might not bother with torches or other lights. Small but distinct points like these are great ways to give locations an identity without making drastic changes and complicating planning.
An important aspect of any new environment is to give players a chance to learn about it first. This can come from their own character backgrounds or knowledge checks, but we would always advise having other characters that can answer questions for them. These could be locals, other travelers, or simply someone who is well-read. The purpose is not to exposit all of your notes to players, though. Have the information be given from the characters’ perspectives, basing it on local knowledge, first-hand experiences, and even rumors. You can use this to separate the information between characters. You reward players for seeking multiple sources and effectively conversing with the people. The ranger might be able to find the way, but it’s the bard that learns about the rumor of cave trolls on that path.
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Once you understand your cave adventure’s setting, it’s time to drop players into it. This is when we use all the effort of establishing the environment to challenge and entertain players. Even outside of encounters, we want the unique characteristics of the environment to shine through and remain everpresent.
Explain, but Engage
One of two important aspects of keeping pace and immersion in cave adventures is to avoid a common problem: don’t let your caves be boring. This applies to every environment but is especially pertinent in caves. The constant darkness and stone with little additional detail can become very repetitive for players, which can then result in losing their attention. You should work to deal with this on both the large and small scale.
The first is what we mentioned earlier about incorporating different biomes into your cave systems. Just like the surface world, extended cave adventures should move through areas that look distinctly different. This works to make each session and ‘chapter’ of an adventure feel refreshing and unique, providing players with new sights to see, details to investigate, and challenges to overcome. These areas should be large enough that the party spends time there and is able to learn and adapt. This can also mean having them appear gradually, or including signs of what is coming, to let players adjust and plan as the new environment becomes more prominent. It also integrates them into the world more smoothly.
When thinking about the variations you can include, we find it easiest to start with broader ideas. Identify smaller features or details of caves and then increase those in size or scope. An example is a stream that cuts through a tunnel. Simple, right? This is a basic addition in itself, but what if it leads to a large pool? Maybe a cavern is flooded, forcing players to dive underwater and navigate through sunken tunnels. The same can be done for almost any other feature of a cave. Mushrooms could develop into a fungal forest, while magma could be flowing from a fire giant stronghold or the chambers of a volcano. You can start with a basic root idea and use that to find inspiration, or look at encounters and build from those.
In addition to the regions themselves, remember how much caves in general can vary. Your cave adventure can take players through tight, constricting tunnels, or into vast, expansive caverns. These variations are a great way to emphasize areas that are not settled or often traveled. They can play heavily into encounters but also serve to keep players interested and imagining the situation. You can use them to liven up the less characterful tunnels, as well as differentiating the landscape within your more interesting regions.
On a smaller scale, and for single cave encounters, you want to create minor variations within these regions. The idea is for each description of the environment as the party moves to be different from the last. These changes only have to be minor, as you will usually be avoiding having multiple occur consecutively. They should be broken up by encounters, conversations, and other player-driven moments, to keep a moving pace.
Much of the technique of this comes from your delivery and vocabulary. This can seem daunting but you can break it down to focusing on a different feature with each description. While the tunnel might not change, elaborating on a certain feature with each description can feed players information in a less repetitive and more attention-grabbing, memorable way. This could mean talking about rock formations one time, the shadows in the cave another, and an animal scampering alongside them for another. You can even write a basic list of these beforehand. If you find yourself unsure or running out of ideas, focus on one of the five senses in each description. What do the shadows look like? Is there a sound echoing? What does the air feel and smell like?
These small travel descriptions are also a good habit to develop for introducing encounters. When clues or signs of danger start appearing, they won’t feel abrupt or out of place, and your players are more likely to be attentive to these details. But more on that in the next section…
Challenges to Face
The other way to keep players engaged is to simply keep them playing. There’s no reason to not keep your party thinking and rolling dice outside of encounters, as they are the best, most direct ways to keep players interested. This might mean them facing obstacles that aren’t involved enough to be encounters of their own. Or they could be general challenges that characters face in order to traverse the environment. All of these are great ways to set the environment apart and really demonstrate its unique dangers.
Our first example plays into the different regions and features we previously discussed. To put it simply, some of these should act as hazards that require planning and the use of abilities and skill checks. There is an almost limitless number of ways to do this, which is why it is often best to establish the environment and its characteristics first. These will give you a base to build from. Try to use a variety of challenges that require different skills, rather than defaulting to perception and athletics. You might include poisonous plants that require knowledge of nature to identify, sleeping creatures that motivate stealth, or survival to identify a path across a cracked, collapsing floor.
As always, variety is the key here. Do what you can to vary the obstacles as your players move, making them think in different ways rather than repeating one strategy over and over. Include both immediate and prolonged hazards, such as surviving the heat of volcanic tunnels through constitution checks. You can repeat one for an extended time, a series of inclines or cliffs that require climbing, for instance, as a way to add a factor of endurance to what could otherwise be a single check. If you do, just make an effort to change it up for the next obstacle or environment.
You also have the option of including survival challenges throughout your cave adventure. These will not be for every party, but they can be a great way to add pressure to a risky endeavor. Underground networks are inherently devoid of food and water sources. What they do have, players can rarely see from a distance and navigate to. You can use the food limitations to create an organic time limit for survival before the journey becomes much harder. This can then play into the difficulties of navigation, as simply getting lost is a very real concern in many caves. Both of these become much less impactful as parties grow stronger but can be used to great effects at lower levels.
An important note is to not let survival challenges feel tacked on. Use mechanics that are linked to the party’s goal. If they are trying to find a rumored location, navigation becomes more important. The same goes for food if they are on a long-distance journey. Furthermore, include obstacles and encounters that make use of or interact with the challenges. An encounter might come with a way to avoid combat, but doing so will mean a detour on a path they are unsure about. Perhaps it has the possibility of locking off their intended tunnel, or rewarding them with a better option? Survival mechanics should be justified and meaningful, as they otherwise run the risk of becoming annoying distractions for players.
As Danger Arises
As your cave adventure continues, the players will eventually come to an encounter. This is where your descriptions will smoothly transition and your design of the environment will manifest in a battle map. But your job begins before anyone else at the table knows what’s coming. Caves are rife with opportunities that other environments do not share, but they also come with other considerations to keep in mind. Knowing, understanding, and using these are key to running your encounters.
Using the Environment
When constructing encounters, attention must be paid to the environment. The characteristic features should feed into both the battle maps and the encounter structure, to highlight the terrain and set it apart from wherever the party last adventured. Fortunately, we have already established a variety of biomes and covered the importance of diversifying your visual features. This mindset will act as the basis for creating unique and engaging encounters.
The most obvious aspect is simply using a variety of maps. Much of this will come from your changes in biomes and encounter-specific features, but you should also pay attention to smaller details. A problem I personally ran into when I first started running games was when multiple encounters occurred along a road or in a forest. It is easy to randomly place trees and rocks, but that quickly becomes boring for players. To avoid this, start by identifying your available resources, and then think about how those can affect a fight.
Perhaps the most obvious example is simply the cave walls. Dividing rooms and creating sightlines can instantly make fights more interesting. Players must fight to stay together as monsters try to separate them, movement must be planned and thought out, and both sides have the ability to hide and take cover. It even plays into the use of light, which we will cover next. As they are natural environments, you can even create the shapes of the cave map randomly instead of trying to carefully plan it.
The next step is using elevation. Splitting your map between two or three levels can work to further emphasize visibility while also introducing skill checks and movement penalties. Sliding down a slope or dropping off a ledge is quick, but might require an acrobatic landing to not fall prone. Meanwhile, climbing up an incline will slow most players and possibly require an athletics check. Both of these force players to think about not only where they intend to move, but how. This goes doubly for if they split up. It can also reward and highlight players that chose skills or tools to deal with these obstacles. Just remember, all of this also applies to whomever they are fighting.
We can also make use of areas of difficult terrain and movement impairment. This could mean fast-flowing streams, loose debris, webs, or sheer drops into darkness. These all act as natural ‘traps’ to decorate your battle map. They are great ways to show the hunting strategies of certain creatures or to divide the map in the same way that elevation changes can. The key difference is in their differing levels of danger, as failing to avoid these obstacles could damage or restrain a player (spider webs), or even change the battlefield in some way (parts of the floor or roof falling away). This is balanced by them tending to be more obviously visible, allowing players to use them to their advantage.
Finally, make use of the challenges we discussed before. You can incorporate the same obstacles and skill challenges of your environment, only now as part of an encounter. While you will not use all of the previous points in every encounter, we would advise trying to include at least one of these. This is to maintain the identity of the region in both visuals and game mechanics. The best part of using these is that players will already be familiar with them, so the added danger will not feel cheap. It will come across as a natural progression, with the party having time to adapt and plan for the new obstacles.
As we mentioned before, try not to repeat the same features in multiple, consecutive encounters, unless it is a specific feature of the area. Your regional features can be ever-present but the rest should be spread out to avoid repetition. If one encounter is in a web of small tunnels, maybe make the next one more open but with cliffs and a river.
We have a wide variety of underground maps with wildly different features. Here are a few, with more in our gallery…
Of course, varied battle maps can only go so far if every encounter boils down to “kill the enemies”. You want your encounters’ structure and objectives to be just as varied. Perhaps the best way to start doing this is by reducing your party’s goal in the encounter to a few words. If you find them often being the same, try to change that. This could mean shifting it completely, adding a secondary objective or development, or giving players more ways to succeed. One encounter might be “kill the enemies” but the next could be “don’t let the enemies past”, “kill the enemies and save the captive”, or “kill the enemies or escape them”. These might seem like simple, arbitrary changes but they work to diversify encounters from the ground up.
These goals will often go hand-in-hand with your map design. A map with restricted movement or chokepoints can change your party’s strategy, modifying their goal; “kill the enemies” becomes “kill the enemies by doing X“. Much of this will come down to players realizing it but the onus is not entirely on them. You can bake it into your battle maps using the features we discussed above. The reverse is also true, though. A map that does not accommodate their goal can motivate them to take control and change it. Think about what challenges you want them to overcome, trying to reward preparedness without overwhelming them.
A simple example of this would be monsters making their way out of a cave, near a town. The party’s objective is to stop them. Now, do they fight the creatures, not knowing their full numbers? Or do they collapse the tunnel and hope that is enough? Both could work but come with their own risks that could be overcome with more investigation and planning. Within the encounter, players will find a battle map centered around the cave entrance. One half is inside, with tight movement and poor lighting. But the outside is open, taking away the party’s control of the situation. A creature making it past them can quickly divide the party, shattering their control of the chokepoint, or even dash away and begin its hunt. All of these factors work to make players think about their environment, using or changing it to fit an otherwise basic objective.
You’ll notice we repeatedly mention the idea of ‘control’. This is because the power dynamic of an encounter can greatly influence its tone. Who has the advantage in an encounter? Obvious examples of this are monster lairs that actually grant their owners additional abilities. But it also applies to ambushes and the use of stealth/perception checks. These will often come down to how your party utilizes their skills and the clues of the encounter to gain an opening advantage. You can manipulate and vary this between encounters to create more subtle variation. Two encounters with the same goal can feel very different if one places the party as underdogs and the other has them open with a surprise attack.
Signs and Sounds
Laying clues in the lead up to encounters helps them feel natural and lets players prepare. There are general rules for doing this, but caves also come with unique factors to incorporate. First, simply consider what might be present. Look at what you have planned for the encounter, most notably the monsters and region features, and think about how far away these might begin to appear. This links back to what we discussed about spheres of influence, with particular creatures seeking to demonstrate their control and others hiding it. Use these to create clues that show the monsters’ intent, behavior, and physical features. They will begin to slowly appear, hidden as part of your travel descriptions, before growing more prevalent near the encounter or within the creatures’ territory.
There are two reasons we do this: to integrate encounters into the world, and to let players slowly discover and plan. The former point links back to our efforts to create a living, interconnected world. People and creatures influence the world around them, whether that be by intentional changes or simply leaving behind evidence. For players, this means a way to learn about the encounter before rolling initiative. Signs of any weapons or tools, shed fur, or previous victims all allow the party to gather information. This is not always possible, as some encounters function as ambushes or accidents. But, when appropriate, these little details provide opportunities for players to use their skills and act intelligently. They can also pose risks, as the party might make incorrect assumptions.
Underground tunnels and even cave entrances also uniquely interact with sight and sound. Constant darkness, as well as twisting and bending tunnels, can obscure details while also making distant light sources more obviously visible. This should play into your use of stealth and perception checks. Shining light can lead to a group being exposed without being seen directly, giving their enemies time to prepare and surprise them. Conversely, darkness can act as dynamic cover, particularly for those with long-range darkvision. This can go both ways. Limited vision can create moving battlefields within your map, as both sides favor or avoid it depending on their own abilities. If you need to, basing an early encounter around the use of light is a good way to remind players of this.
The enclosed areas also introduce one of the most important aspects: echoes. While light is limited underground, sounds bouncing off of cave walls can actually increase the range of perception checks. But this comes with caveats. Namely, echoes can lead to the sound being directionless or indistinct. You can use this as the first clues of an encounter, with a perceptive player hearing echoes of movement or chatter. Like the other clues, this will become more obvious and distinguishable as they near each other. The same can be said for if the party is constantly talking or roll a low stealth check. Again, this can give an advantage to either side, depending on how they adapt to use it. Echoes can also play into the consequences of encounters, which we will discuss in the final section.
These two senses are important due to the nature of caves and the creatures in them. Like real-life animals, many native monsters will have evolved to favor hearing over sight. This can help emphasize your players being foreign to the environment, as they have a limitation that their enemies do not. It again plays into the feeling of isolation, with the party being trapped within their light or darkvision. The fear of the unknown can be a great way to ramp up the tension.
Once the Storm has Passed
But what about after the encounter, when players take a breath and prepare to move on? This is where you will likely either return to your travel sections or begin the transition into another encounter. As you do this, there are things to keep in mind. Cave adventures come with unique consequences in addition to the regular effects on a party’s survival, reputation, and coin purses. These are important to remember, as they can change the pace and structure of the players’ journey.
The first difference of caves is one we have already discussed in the reverse context: echoes. To put it simply, encounters are loud. If players do not act in a way that minimizes this, it is possible that the noise of their scuffle can attract other, unwanted attention. This allows you to add more danger to certain environments like large nests and lairs. The risk of being instantly drawn into another fight will prompt players to act stealthily and with caution. Just be sure that they know this, or give them time to learn instead of instantly bringing a cave’s worth of monsters down on them. It is important to use this threat sparingly and fairly, so you might even limit these reinforcements to when players use thunder damage. Of course, nothing is stopping you from describing other echoes to create tension, even if nothing shows up.
Another possibility is a change in the environment. As we mentioned in the challenges, encounters and other obstacles can often come with options or consequences that change the path the party must follow. This could come from a simple deviation, or something as extreme as collapsing a tunnel. Both of these relay back to the feeling of survival, even if it is not mechanical. Having their plans disrupted by a fight going badly applies pressure without you needing to do much at all. In the most drastic cases, a cave-in might trap or separate the party. Just remember that your goal is not to punish your players. Not every encounter needs these kinds of consequences, and those that do should be posing a new challenge to overcome rather than simply taking something away.
Always remember that these results should be both positive and negative, depending on the choices the players made. You can reverse the consequences we describe in order to reward players for a well-executed encounter or successful plan. When appropriate, the sounds of their fight could draw help from another group. Sneaking past a fight or quickly ending it could lead to them finding a shorter, safer tunnel. Not all rewards need to be monetary.
A final consideration that plays into many others we’ve covered is the use of time. Parties traveling underground, without any special skill to do so, will need to estimate the passage of time. The official rulebook places limitations on the number of rests a party can take, but you are able to waive this for your cave adventure. Instead, incorporate the characters’ energy levels into your travel descriptions after encounters. You can blend this especially well into survival resources by giving players total control over how long they are willing to push themselves before resting. A long rest will consume a ration, forcing them to balance their food supplies with their hit dice and abilities. This is all to simulate their ‘internal clocks’, acting as the final point of maddening isolation in a cave adventure.
That’s it for your journey through the underground and all its many wonders. Keep an eye out for the complete PDF, coming out soon! In the meantime, feel free to return to our cave encounters with this new information. You can also leave a comment letting us know what you think. We’d love feedback or to hear about any cave adventures you’ve run! You can also browse our other articles for similar guides on other environments and creatures.
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