What Lurks Beneath - How to Run Burrowing and Diving Creatures Effectively

Your party rushes towards a mound of treasure, the aim of their quest. After journeying for days, they are eager to get to their quarry and go home. But as they near the hoard, the ground beneath them rumbles. Suddenly the earth erupts, and a pair of creatures appear. They scurry excitedly towards their potential meal, and a battle begins. 

The party engages, and the fighting is exciting… until the creatures burrow back under the ground. Then the party waits, unable to react until they have the creature available. Moments go by as everyone waits. Suddenly, the creatures appear again. The party, having waited for their foes to approach, unleashes all they have in a flurry of excitement. The creature takes the damage, lashes out, and… goes back underground. This change in the battle rhythm continues on for a few minutes until both creatures lay dead on the ground in front of them.

If you have used burrowing creature at your Dungeons & Dragons games, you have probably run into a similar experience. Burrowing creatures can be extremely exciting in theory, but can create an unsatisfying combat in practice. I was discussing this rrecently while helping create a monster for Thimbleton Inksquire’s Runic Compendium. We could identify some problems and come up with some solutions.

The Problem

When a monster uses its burrow, it can remove the choice from the party members. When the creature leaves the visible battlefield, the PCs can no longer interact with it. This leaves them with limited options, and forces them to act more reactively. Players will often hold their action, hoping to attack when the creature erupts from the ground again. Often it feels like a dead turn, since the party is waiting for something to occur. The party must stay vigilant, but they can do little more than that.

Since the party’s actions all hinge on the monster surfacing, it means that the moment the creature appears, the PCs will pummel it with attacks. This means that all the potential damage a monster would take gets compressed into one moment. Strategically, this means any burrowing creature will benefit from staying underground as long as possible, making the most out of its chance to catch an enemy by surprise. While this makes the most sense tactically, it means that the problems of pacing in combat will repeat. The monster surfaces and gets attacked. It attacks a party member and then burrows again, repeating the process. Your table will end up spending most of their time holding their turn, which leads to a choppy and messy combat. But we can change that.

Solutions

Now that we understand where the problem comes from, we can devise some solutions on how to resolve this. I am going to break these up into two groups: Player Options and Monster Options. You can use one type or both depending on how much complexity you want to bring into your game.

Player Options

A lot of the problems that come from burrowing combat has to do with the fact that the party becomes unable to perceive the monster while it is underground, while the monster can still detect the party. These monsters will have some sort of sense that allows them to detect their prey.

Looking at the Ankheg in the SRD, it has Tremorsense, which allows creatures to use vibrations to detect enemies. This means that any creature walking along the ground will give its location away to the creature, allowing it to pinpoint its target and attack them from below. This effect does not work on flying or incorporeal creatures, since neither are technically touching the ground.

The easiest ways to fix this problem are to give your players some additional actions they can use while a monster is burrowing. Actions such as detecting and hiding from their foe mean they will have choices beyond waiting for damage to occur. While your players cannot see the creature, they might have other ways of locating them.

Sense Creature

You can give your players the option of trying to detect where the creature is underground by using an action to “listen” for sounds of burrowing. When creatures are burrowing under the ground, they will not be entirely silent, so a player could find a burrowing monster with a high enough Wisdom (Perception) Check. Such a check will usually be difficult for any player character, unless they have experience with dealing with subterranean foes.

Hide From Sight

For players, you can give them the option to use the Hide action, stilling themselves enough so that the creature will not see them. When a player uses Hide, have them roll a contested Ability Check, the player’s Dexterity (Stealth) vs the monster’s Wisdom (Perception). They can forgo the chance to attack by having time to become unseen by their enemy. You can optionally allow for Advantage if the PC can get on higher ground (such as standing on a boulder or cart) and Disadvantage if they have to move (unless someone trained them to move properly.) So now your players have a little more agency in determining how battle goes. 

While these strategies can allow us to create entirely new creatures, we can usually just keep these in mind for adapting out existing creatures that have burrow. A lot of the burrowing creatures, such as the Ankheg and Purple Worm, already have Tremorsense built into them. Giving your players the ability to “hide” from these creatures can give your players a lot more options immediately, giving them a reason to try stealth.

Monster Options

Now this gives the players an additional option, but what about the monster? As I touched on earlier, the monster has little reason to stay on the surface, so we need to give the monster something that gives them some sort of advantage while on the surface. Certain stronger attacks might only happen if the creature starts their turn above ground. Maybe our Ankheg has a Charge ability that requires them to move in a certain direction above ground to hit harder. But I have a more interesting option.

Echolocation

Looking back at the tremorsense, one of its biggest weaknesses is that it does not work against flying or incorporeal creatures. What if we gave the creature an ability to fix this? We can create some sort of above ground “Echolocation” ability that allows the enemy to pinpoint all creatures. The caveat is that they can only use this ability above ground. This can last until the creature’s next turn, or be an effect they need to save to get rid of, almost like faerie fire. The flavor I came up with would work best with creatures that have little to no vision besides Tremorsense, like bats or moles. Alternatively, we could have it have similar effects to Faerie Fire. Creatures affected by this Echolocation will vibrate for the next minute, allowing any creature with tremorsense to hit the creature with advantage. Now our creature wants to stay on the surface to do more damage, providing them a reward for their risk.

Larger Battles

Adding a mix of burrowing and non-burrowing monsters can create a more balanced encounter. Having both means that when one monster burrows underground, the party has to make a choice. Do they prepare themselves for an underground attack, or do they deal with the enemies they can see? One way you can do this is to have the monsters have above ground allies. In our Ankheg example, this could mean Ankheg Larva or Young, non-burrowing creatures that can still present danger to players. You can take this a step further, and give the Larva the ability to signal to their burrowing parents they need help, adding a complication to attacking them.

You can also have them as a third, neutral party that also needs to worry about the threat below. Members of a rival adventuring party have come across one another while trying to loot the nest of a Purple Worm. They can attack one another, but loud sounds might draw the attention of the inhabitants. This can be extremely fun as now both sides will now have to worry about drawing attention to danger lurking beneath, and may even want to use the worms to their advantage.

Examples

Now that I have discussed some options, let’s go through some examples of how to use these concepts in combat, with some encounters that I have come up with. 

Giant Mole

While normally docile, the Giant Mole spends most of its life under the ground. It normally feeds on bugs and larva, but it does occasionally come up to the surface if it thinks there is a potential meal or creature in its territory. While solitary moles are not uncommon, these creatures will often live in small groups, sometimes with a larger Alpha Giant Mole leading the group. Anyone that has spent enough time around the moles knows to keep their movements as quiet as possible when crossing mole territory. Any Ranger who travels the area long enough will even develop a specific way to walk that keeps their movements unnoticed.

Giant Moles are effectively blind, like their smaller relatives. They rely on Tremorsense to supplement their limited vision. While on the surface, however, they can use their Echoing Screech ability. This earsplitting sound causes creatures to vibrate, giving the mole’s senses a picture of all creatures in the area. Once a mole goes underground, however, the effect will quickly end. If a mole wants to use this effect, they will often try to stay on the surface as long as possible.

The Eroding Hand

A cult known as The Eroding Hand seeks to bring about the end of civilization, viewing it as a blight on the world. Their goal is to empower nature to rise up and dismantle structures and buildings, one at a time. One faction of cultists is currently attempting to provoke a local earth elemental, Rokthorr, into destroying a nearby village.

Upon arrival, the party encounters a mix of Acolytes, Cult Fanatics, and Thugs led by the the Earthshaker Adept. If the party tries to clear them out, the leader summons Rokthorr to attack. As the party attempts to defuse the situation, the cultists do everything in their power to hinder the party, forcing them to focus on the cultists while Rokthorr burrows underground. The party must now choose whether to prioritize clearing out the Cultists or dealing with the Elemental that strikes from beneath the earth sporadically.

As a note, the Elemental can either be an ally of the cultists, or be a third party that reacts to sounds. The second will create a more complex encounter with a much more dynamic environment.

Final Thoughts

When you have burrowing creatures, there is a danger of creating an unsatisfying encounter for your table. On the player side, you can end up with combat that robs your players of choice as they wait for the creature to surface and launch their attacks, reducing their turns to just holding their action. Your burrowing creature will end up getting pummeled the moment it surfaces, adding more reason for it to attack from beneath. But with some minor adjustments, we can avoid this by increasing the options available. Giving monsters options they can only do on the surface means that it can be helpful for a creature to avoid burrowing in order to get some sort of advantage. Giving your players more options, such as hiding their motion from tremorsense, they may control where the creature appears. Simply adding in some enemy units will mean that the players will have to split their attention, as both threats will cause them harm. If you use any or these strategies, you should be able to avoid having a lackluster encounter.

Are you looking for copies of some of the statblocks I mentioned? Come take a look here! In the future, I hope to release a more polished document.

How do you use burrowing creatures in your game? Do you have any tricks to keep them interesting? I would love to hear about them below!

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