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A Colony, Contaminated 5e Encounter - Banner - Small

Forest and cave encounter with ankheg variant creatures, with stat blocks for use in D&D 5E.

A town’s lumber industry is in peril. Its recent progress into the surrounding forest has been met with attacks by ankhegs; giant, ravenous insects. These ambushes, which grow more frequent, have already resulted in two deaths and many more injuries, greatly slowing the woodcutting as workers fear the deeper forest. To stem the tide of attacks and motivate the lumberers to return to work, the town has placed a price on the ankhegs’ heads. Anyone that returns with proof of a kill will be rewarded. The bounty has seen several adventuring groups respond, though most have returned with more scrapes than prizes.

As of yet, no one has figured out the reason for the ankhegs’ growing hostility. The truth of the matter is that the creatures are lashing out in response to the poisoning of their nest. Lumberers have been dumping their waste, including the local trees’ poisonous sap, into the stream that their logging path has followed. This stream flows down into the caves where the ankhegs make their home. The growing pollution and the hatchlings it has killed have whipped the ankhegs into a frenzy, causing them to hunt more viciously and further from the nest than they usually would, bringing them into contact with the workers. The worse their nest is affected, the more they attack.

Bug behavior bavardage. Anyone staying in the town and paying attention to its residents is sure to hear discussions of the ankheg problem. If a character eavesdrops on or engages with one of these conversations, they learn that the town has always known of the ankhegs. The creatures have always lived in the forest but were rarely encountered, as they would normally stay in the deeper forest and away from the sounds of the woodcutting. The townspeople speculate that something must have changed to make them more violent. From there, the conversation devolves into baseless gossip. This includes guesses of a hag controlling the ankhegs in revenge for the previous mayor’s secretive past, rival lumberers baiting the insects in order to destroy the town’s industry, and other outlandish conjecture.

Fellow bounty hunters. Another trio of adventurers is currently staying in town and hunting ankhegs. When encountered, the group celebrates the party’s arrival and is happy to speak with them. Much of the conversation centers on either side’s previous experiences, as well as how long the characters intend to stay in town. In regards to the ankhegs, the adventurers mention the increased density further in the forest, explaining that their group has stuck to hunting the outskirts after a harrowing encounter on their first day of hunting. They advise the party to do the same. As part of this warning, they recount the aforementioned encounter, which ended with them running from a larger, stronger ankheg that their weapons struggled to harm. They are apprehensive but agree to give directions to where this fight occurred, should the party ask them to.

Timber Brook - Clear - Day - 44x32

The Timber Brook

The walk is serene, turning to take you alongside a flowing stream that cuts through the grassland. The gentle sound of the water blends into rustling grass and leaves and the crunching of dirt beneath your feet. Just as you begin to relax into the gentle breeze and warm sun, the serenity is broken. Ahead of you is the edge of the forest, welcoming visitors with a camp of lumberers that shout to and at each other as they trudge between piles of felled logs.

The timber brook is the site of the lumberers’ most recent camp. Their constant logging has pushed the forest back to this point, where the trees cut in the immediate area are being gathered to be returned to the mill. The camp itself is extremely basic, owing to how often it must be moved. It features only a small space for a campfire beside the road, several basic shades for sleeping under, and a bridge that would cross the stream were it not freshly broken by a falling tree. Up to a dozen lumberers are currently moving within and around the camp, depending on the time of day that the party arrives. They pay little mind to the characters past a curious glance, though whoever is in charge of the camp does come forward to greet the party, brusquely asking their purpose for visiting.

Speaking to the supervisor. The characters can talk with the camp’s current supervisor to gain some information about the creatures in the forest. The supervisor cannot name the monsters but gives a vague description of an ankheg. They also mention that the group should, “watch out for the acid spit; you don’t want to see what it can do to someone.” Finally, they advise the characters to always keep an eye on the ground, where the creatures hide, but also warns them that some workers have spoken about hearing loud buzzing from high up in the trees.

Workers’ waste. The workers within the camp are quick to dump various forms of refuse in the stream. A character that looks around the area notices the broken bridge, as well as several logs that have been left in the water. They also see lumberers discarding scraps of food and unemptied bottles, and even pouring out sap collected from the trees, all to be washed away. 

If the characters inquire about the behavior, the workers shrug off the idea that the litter is a problem. Should the party ask about the sap, they are told that it is poisonous to consume or handle for long, and can even give off fumes, prolonged exposure to which is dangerous. As such, they must drain it from the wood and then they simply discard the sap in the most convenient way.

Map and Assets Downloads

This encounter is designed to fit without two of our most recent maps: the Timber Brook and the Pooling Caverns. These maps make the lumbering camp and the ankheg nest, respectively, but we have plenty more maps and assets that you can use for the party’s time in the forest, including other locations where you might want to place the camp…

Pooling Caverns - Limestone - Light - 44x32

The Pooling Caverns

The stream snakes through cylindrical tunnels that wind through the stone. Echoes of trickling water reverberate from every direction, bouncing in and out of smaller shafts that each twist and fade into darkness. The sound grows louder as you step further, feet sliding across slick stones, as does a noxious smell that prickles the inside of your nose.

The ankhegs make their nest in a set of caverns which they have burrowed additional tunnels throughout. These caverns are deep in the forest, at the end of the same stream that cuts through the lumberers’ camp and comes to an end in a pool at the caves’ center. These central spaces are used to safely house the ankhegs’ eggs and young hatchlings. Recently, the water that flows into the caverns has been polluted by waste and poisonous tree sap. This pollution and poison, which collects in the pools, acts as an irritant to larger ankhegs but is far more dangerous to their young. It has resulted in many of their eggs and hatchlings dying, contributing to the attacks throughout the forest.

Collecting contamination. Characters exploring the ankhegs’ tunnels may be able to recognize the pollution that is building up in the water. A character that succeeds on a DC 15 Wisdom (Perception) check while within the tunnels notices a thin buildup of sludge that coats the stone beneath and around the stream. If a character inspects the sediment, they can identify it as the source of the smell within the caverns. A character that rolls 17 or higher on their check also spots several shards of glass that have washed into the cave, which are identifiable as pieces of the same bottles that the lumberers drink from. 

A character that is aware of the sediment can make a DC 13 Intelligence (Investigation) check to realize that the buildup is greatest on the surfaces of rocks facing against the current, suggesting that it has gathered from the water that flows into the caves. 

Finally, a character can make a DC 13 Intelligence (Nature) check to identify the sludge as tree sap. They also recognize that it is toxic, enough to harm grown ankhegs and potentially kill their young.

Ankheg Colony

The forest is home to a colony of ankhegs, with the center of their nest found in the network of burrowed caves. These ankhegs come in various shapes and sizes, each fulfilling a different role in the colony and representing a different danger to those intruding upon their territory. Anyone walking the forest must keep an eye on the earth below and the trees above, or else become food for the colony.

Ankheg Crawler

It is an insect, close to the size of a human, that is plated in mottled brown chitin. Its long body is supported by jagged, hooked legs and ends in a head of eye clusters and vicious mandibles.

Ankheg crawlers are smaller and weaker variants that act as drones for the larger colony. They are often more numerous than others and spend their time tending to the colony, whether that be by burrowing new tunnels, clearing others of waste, or caring for new hatchlings. The crawlers are less aggressive than the regular ankheg and it is much rarer for them to act as hunters, but they are still a threat to anyone that finds themself the crawler’s target. Perhaps their most dangerous feature is the ability to hold onto and hide amongst trees, owing to their smaller size and alloying them to ambush prey that is focused on searching the soil.

Ankheg Hunter

Buzzing wings hold an insect aloft, its body like an oversized wasp protected by a thicker, brown exoskeleton. Its long legs are curled beside its body and a bifurcated stinger caps the end of its abdomen.

Though it is the smallest and perhaps least threatening of the ankhegs, the ankheg hunter is also the only variant with the ability to fly. The hunters act primarily as scavengers that transport the remains of their kin’s victims back to the colony, piece by piece, for them to be consumed. But it is the hunters’ other role that earned them their name. Their aerial speed allows them to buzz through the treetops in search of prey, before hugging to the trunks of trees and using their vibrations to alert other nearby ankhegs to their target’s location. By the time someone walking through the forest recognizes that the buzzing is following them, it is likely too late.

Ankheg Guardian

The insect’s mandibles chitter as its many thick, armored legs claw forward. It resembles others of its kind but with a greater exoskeletal that seems to part only for its eyes and mouth. Its foremost arms are also far larger, coming to serrated points behind wide, almost shield-like plates of shell.

Anything that finds its way to the entrance of the ankhegs’ colony is sure to be welcomed by ankheg guardians. As their name would suggest, guardians act as protectors of the nest. They fulfill their role with deathly seriousness, killing any intruders long before they can threaten the ankhegs’ young. This is made all the easier by the guardians’ thicker exoskeleton and powerful claws that can quickly overpower prey caught in the confines of the colony tunnels.

Balancing the Ankhegs

The ankhegs spread throughout the forest are designed to be just that: spread out. The party can encounter groups of different sizes as they hunt, with the ankheg packs throwing stronger and more numerous as the characters approach the nest. This helps simplify the encounter’s balance in two ways. 

First, you can dynamically adjust the balance of each combat section within the larger encounter. You can begin by selecting both a CR value and a number of ankhegs that is equal to or lower than the party’s level and size as a test of what they can handle. Use what you learn from this combat as a basis for balancing other ankheg groups. Remember to still keep some variance in the difficulty of individual fights to ensure they feel like natural encounters and to add risk to the party’s decisions.

Second, it is up to the party to decide how far into the forest they explore and when they turn back. As long as each group of ankhegs is individually manageable, the risk of the encounter is placed in the characters’ hands rather than yours. This saves you from having to predict and balance around how they might have prepared for the day, how they spend their resources, or what risks they are willing to take, as you might need to for a single, larger encounter.

The party’s control comes into further effect with the encounter’s conclusion. There are many ways that the characters may or may not solve the town’s issue, ranging from simply hunting ankhegs to discovering the nest’s pollution and confronting the lumberers. This means that fighting the more difficult ankheg guardians is ultimately optional and is not required for the party to be rewarded or feel that they ‘completed’ the adventure. It only needs to go as far as the characters choose or are able to figure out.

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Troy McConnell

Part-time DM and author of 2-Minute Tabletop's encounters, map lore, and characters. Basically, I write about all the campaign ideas that I don't have time to run. All with the assistance of my feline familiar, Wink.

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