Deadliest Dungeon Designs - Kobold Cave - Hard Encounter for Six 3rd Level Characters

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Doom Intro: Every evil DM I know works damn hard and honestly deserves a little vacation. So to that end, I’m taking you all on a trip to a seaside paradise! And nothing says “seaside paradise” quite like a desolate beach surrounded by jagged rocks, a teeming warren of over-ambitious kobolds, and a bunch of clever traps and ambush points. Welcome to Kobold Cove! Are you ready to see how this dream vacation plays out? Let’s take a look...

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Hook: A local druid tells your party of an unnatural pall of smoke that has appeared at a lonely, rocky point on the coast nearby. The druid suspects powerful magic, and fears that the delicate balance of nature has been upset. He offers to loan the PCs his small rowboat for use in investigating, and to give them two specially brewed potions as a reward when they return.

With that, he points them south and sets them on their way. 

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Background: A pair of kobold twins, Krek-Krek the Clever (a male kobold inventor - Volo’s Guide to Monsters, pg. 166, with a few extra inventions) and Slaggsy the Scorcher (a female kobold scale sorcerer - Volo’s Guide to Monsters, pg. 167) were noted for their intelligence by their master, Ichoramiux, a black dragon. She sent the ambitious twins on a mission to search for a mysterious artifact which she believed was buried on a mountainous peninsula on the southern coast. After booby trapping the site against intruders, the twins’ small tribe of kobolds began their excavation. Months of digging eventually unearthed the tip of a mysterious, rune-covered metal object. Slaggsy, drawn to the power of the artifact, began to experiment with it. This triggered a reaction in the device, which began belching out acrid black smoke. 

Unnaturally dense and low-hanging, this is no ordinary smoke. The artifact maintains a direct connection to the Elemental planes, and the smoke is actually elemental seepage from the demi-plane of smoke. Thrilled by this display of power, the kobolds have continued their excavation, attempting to unearth the entire artifact so they can bring it back to Ichoramiux for a hefty reward.

The smoke has gathered around the small cove, shielding it from most sunlight and limiting the visibility there. This enables the kobolds to operate out in the open without triggering their sunlight sensitivity. The area is considered lightly obscured, making it more difficult for the PCs to detect any of the kobolds’ traps and ambushes.

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Area 1- The Cove

After an uneventful row down the coast, the PCs spot the swirling black smoke shrouding the tip of the lonely peninsula. They spot a small cove, the only potential landing spot for their little rowboat. A DC12 Wisdom (Survival) check will confirm that this is, in fact, the only safe landing. The best bet would be on the eastern side of the cove, where the terrain is somewhat flat between two craggy rocks. The cove’s northern wall is slick with seawater and very steep, requiring a DC 18 Athletics check to climb it. 

A massive column of black smoke curls menacingly behind this towering northern wall (Area 4) making the entire map lightly obscured. All sight-based perception checks will have disadvantage. 

But before the PCs can land, they must contend with Krek-Krek’s first booby trap: a thin alarm wire strung across the entrance to the cove (yellow line in Area 1). PCs can make a DC 15 Wisdom (Perception) or Intelligence (Investigation) at disadvantage to spot the wire. If the wire is tripped, bells and alerts will ring out, sending the kobolds scrambling to ambush positions. If it’s not triggered, the kobold ambush is more slapdash, but still fierce.  

Area 2- Landing 

Here there be Kobolds! Hidden among the craggy salt-covered rocks lies a secret exit from the tribe’s warren, carefully hidden in the stone (Area 2a). PCs must make a DC 17 Perception check (at disadvantage, because of the smoke) to spot it. If the PCs tripped the alarm in Area 1, then the kobolds have an ambush waiting for them. Two kobolds emerge from a narrow path (Area 3a) to lob missiles at the newly disembarked PCs before disappearing out of sight. The kobolds will try to lure the PCs up to the plateau (Area 3) to keep them from discovering their hidden warren exit (Area 2a). 

If the PCs avoid triggering the alarm, they will find this area empty, but may hear the two kobold guards at the entrance to the warren on the plateau above (Area 3d). A successful DC 12 Perception check (no disadvantage since it’s based on hearing, yay!) will reveal the sounds of two kobolds lazily chatting and gaming with bone dice. The rest of the kobolds are deeper within the caves (area 4a) busily digging for their artifact. 

Area 3- Plateau

  As in Area 2, the smoke curls around the barren rocks and the PCs. However the smoke seems slightly thicker here as the PCs are approaching its source. Also secreted among the rocks is the main entrance of the Kobold warren (area 3d). 

Attack Plan

If the alarm was tripped:

Krek-Krek the Clever, true to his name, lies in wait for the PCs with two fellow kobolds in Area 3b. The two additional kobolds are stationed at Area 3a, and two more at Area 3d. 

Area 3b is a very narrow (and conveniently kobold-sized) area. Any creature that is medium sized or larger will need to squeeze to get between the rocks on either side. Using their pack tactics, the kobolds will try to corral the PCs into this bottle neck, making it all the easier to ambush them. This is the kobolds’ turf and they know how to use it. They will use the terrain, their numbers, and their size to their best advantage. 

Krek-Krek, being the inventive kobold he is, has a variety of deadly inventions in store for our PCs. But he has a special weapon up his scaly sleeve: his flinging stick. With this stick and using indirect fire, he is able to launch explosive missiles over the rocks and onto the PCs. The flinging stick changes the range on all his weapon invention ranged attacks to 15/60 ft. When using his flinging stick, he ignores half cover and three-quarters cover for his ranged attacks. Additionally, he can make ranged attacks against targets behind total cover as if they had three-quarters cover.

Close Up Attack

Once the PCs engage with the kobolds two additional kobolds sneak out from the excavation cave (Area 4) and onto the cliff above the cove (Area 3c). From there they will begin raining down the biggest rocks they can lift upon the PCs’ boat with the goal of sinking the craft. The kobolds each have a +4 to hit and each rock does 4 (1d8) bludgeoning damage. The boat has AC 11 and 50 hit points. If they are not stopped, the kobolds can sink the boat in about 5 rounds. The destruction of their boat is the #1 threat to the PCs, trapping them at the kobolds’ cove. The kobolds are hoping this threat will split the party and put them even more on the defensive.

After the first round of combat, a further 3 kobolds will creep out from the hidden warren exit (area 2a) and attempt a surprise attack from behind. They will target casters and the weaker members of the party at the back. Any PC that is not engaged with the other kobolds can make a DC 12 Perception check (still disadvantaged-- pesky smoke!) to notice the incoming kobolds. 

The kobolds are feisty and clever despite their low challenge rating. Their sheer numbers and pack tactics should allow for a challenging fight. If you’d like to kick it up a notch, add another wave of kobolds from the front or rear exits (or both)! If the battle goes poorly, Krek-Krek will retreat down the cave (area 4a) to make a last stand with his sister, Slaggsy. 

Sneak Attack

If the alarm was not tripped:

Two kobolds guard the burrow (Area 3d). They are able to hear any loud noises in Area 2, or see the PCs walking up the ramp into Area 3. They will immediately sound the alarm. 

When the alarm is sounded, Krek-Krek and four more kobolds will rush out from Area 4 and attack the party. On the next turn, two more kobolds will join them. 

When the PCs engage the kobolds in Area 3, four more kobolds will sneak from the hidden burrow (Area 2a) and attack from behind, trying to eliminate the casters at the back of the party. 

Another weapon in Krek-Krek’s arsenal is his Oil of Slipperiness; he has two doses of it in special jars. He can apply the Oil of Slipperiness to the ground as a ranged attack (+4 to hit, range 15/60 ft.) On a miss the Oil has no effect and is wasted. Krek-Krek will try to split the party by lobbing the oil at the ramp leading to Area 3. 

Kobold Warren

Area 3d and Beyond - the Kobold Warren

This very small tunnel system has just enough room for a small tribe of kobolds to cuddle up. If all the kobolds are defeated, the PCs may ransack this area and discover a potion of healing, 11 gold pieces, and a set of Tinker’s Tools from Krek-Krek’s “laboratory”. 

If you’d like to make this into a longer session, you can build out the warren (using our Burrows pieces!) and force the PCs to battle through a series of booby traps, ambushes and deadends. 

Area 4 Overhead

 Area 4 - The Artifact Cave 

The area opens into a water-worn pit in the barren rock with a large, newly excavated cave in its eastern wall. Menacing smoke pours from the cave’s entrance. The scene is littered with evidence of recent excavation.

In Area 4a., Slaggsy and her two kobold “acolytes” dig furiously around the artifact, desperate to complete their task. They will defend the sacred artifact to the death. 

The entrance to the cave is trapped, thanks to Krek-Krek. A pressure plate triggers if any creature weighing more than 60 lbs passes the threshold. Most small-sized creatures, included the kobolds, are too light to trigger it. Any creature who does not make a DC12 Dexterity Saving Throw after triggering the trap will be showered in sticky glue. Thanks again, Krek-Krek. The affected character has their movement halved for one round as the glue hardens. A PC can take an action to wash off the glue using any sort of alcohol. Using water or any other liquid will take two full actions. Characters can also break out of the glue by making a DC 14 Strength (Athletics) check. On a success they can move up to half their speed. However at the end of their movement, they will again become stuck to the ground. 

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The Artifact 

The buried artifact was crafted by dragons eons ago. It functions as an interplanar conduit, channeling magic from one plane to another. A successful DC 13 Intelligence (Arcana) check will reveal this knowledge.

The artifact can be deactivated with a successful DC 15 Intelligence (Arcana) check or a DC 17 Dexterity (Thieves’ Tools) check. If the artifact’s origin is successfully discovered, the PC gets advantage on the check to shut it down. Shutting the device down in this way will reveal the power core which can then be recovered. The elemental core stores a mote of energy that allows the bearer to cast Conjure Elementals one time ever. 

The artifact can also be dismantled by brute force. It has 50 HP, resistance to piercing and slashing damage, and immunity to psychic and poison damage. It is large and immobile so any attack automatically hits. If destroyed in this way, it explodes in a shower of arcane energy. Any PC in a 20 ft radius must make a DC 14 Constitution Saving throw. On a failed roll, PCs suffer 17 (3d10) force damage; they take half damage on a success. As the cave begins to collapse, PCs have 1 round to exit before the ceiling caves, in dealing lethal bludgeoning damage to anyone left inside. As the dust settles, the ground begins to rumble and fallen rocks shake as a twenty foot tall Elder Earth Elemental rises from the wreckage. 

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The Elemental:

This massive, unkillable engine of destruction gives chase to the PCs and will absolutely murder them if they try and fight it. The goal is to give a thrilling “escape by the skin of their teeth” chase back to the boat before they sail back to safety. It should be clear that this is a foe beyond the PCs’ measure; but if they do attempt to battle it, you can use the statistics for a Stone Golem (Monster Manual, pg. 170).


Krek-Krek the Clever is a kobold inventor (Volo’s Guide to Monsters, pg. 166) with the following additional features:

He has 27 HP, and has fashioned himself crude armor increasing his AC to 14.

He’s also fashioned a “flinging stick” which allows him to launch his various inventions further than usual and over obstacles. The flinging stick changes the range on all his weapon invention ranged attacks to 15/60 ft. When using his flinging stick he ignores half cover and three-quarters cover for his ranged attacks. Additionally, he can make ranged attacks against targets behind total cover as if they had three-quarters cover. He carries two doses of Oil of Slipperiness in special jars. This allows him to apply the Oil of Slipperiness to the ground as a ranged attack: +4 to hit, range 15/60 ft. On a miss, the Oil has no effect and is wasted.

Slaggsy the Scorcher 

(Kobold Scale Sorcerer - Volo’s Guide to Monsters: pg. 167)


Krek-Krek has one dose of universal Solvent and one dose of Oil of slipperiness

Terrain Required to Build Kobold Cove: 
1x Erinthor Mountains
1x 12x12 Water/Stone Terrain Tray

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