RPG Evolution: Eat or Be Eaten

Megadungeons, long a staple of D&D, can be just as complex as any other ecosystem in your campaign.

1200px-TrophicWeb.jpg

Picture by Thompsma - Own work, CC BY 3.0, File:TrophicWeb.jpg - Wikimedia Commons

The concept of megadungeons conjures images of sprawling underground complexes filled with untold riches and deadly monsters. But beyond the treasure and encounters lies a deeper level of worldbuilding: its ecology. Considering the intricate web of life can transform a static dungeon crawl into a living campaign. But to make that ecosystem matter to the PCs requires some planning that can make simply killing a monster change the course of the game.

Dungeon Ecology Basics​

For a dungeon ecology to truly resonate with PCs, certain elements need to be in place (see Lew's article on the same subject). Firstly, the dungeon needs to be large enough and have multiple levels to support a diverse ecosystem (Megan Wiseman calls this "Gygaxian Naturalism" after co-creator of Dungeons & Dragons, Gary Gyax). Different levels with varying resources and environments can host distinct food chains and monster populations. A small, linear dungeon simply won't have the space for a complex web of life.

Secondly, repeated visits to the dungeon are key. If the PCs are delving into the same complex over multiple sessions, they're more likely to observe patterns, note changes, and perhaps even develop a sense of how the dungeon "works." Why bother learning what eats what if you're only planning a one-time raid?

Finally, the possibility of PC impact on the ecosystem should be apparent. If the adventurers' actions – whether through hunting, introducing new creatures, or altering the environment – have noticeable consequences, they will be more invested in understanding and perhaps even manipulating the dungeon's natural order.

The basics of ecology involve trophic levels, each with its own level in a food web:
  • Level 0 (Decomposers): Often left off food webs, these involve creatures responsible for breaking down nutrients like slimes, carrion crawlers, and fungi monsters like gas spores and myconids.
  • Level 1 (Producers): Plants and algae make their own food. These include plant monsters like shambling mounds and twig blights.
  • Level 2 (Primary Consumers): Herbivores eat plants. Curiously, there are not a lot of these types of monsters in core D&D. Giant boars, goats, and lizards might qualify.
  • Level 3 (Secondary Consumers): Carnivores that eat herbivores. There predators aplenty, and this is where a lot of humanoid monsters can be found, from kobolds and goblins up to orcs and hobgoblins.
  • Level 4 (Tertiary Consumers): Carnivores that eat other carnivores. The most dangerous of these are apex predators, who have no predators. These are monsters that can challenge entire parties, like dragons and krakens.
Food webs can be incredibly complex, but for a game master's purposes even a simple pyramid can help sketch out what creatures depend on others and the impact of their removal.

An Adventurer's Guide to Subterranean Sustenance​

The anime series Delicious in Dungeon offers a humorous look at a dungeon with an internally consistent ecology. The protagonists frequently consider the ecological implications of their actions, driven by their need to eat the monsters to survive.

A prime example is the episode, "Kelpie/Porridge/Broiled with Sauce." The adventurers observe that a kraken (Tertiary Consumer) has become so successful at hunting the dungeon's mid-level monsters that their populations are dwindling. This leads to fewer food sources for other creatures, highlighting how the removal of too many mid-level prey can negatively impact the entire ecosystem. Similarly, Senshi the culinary dwarf advises the party's spellcaster Marcille to not just blast the flying bladefish (Primary Consumers), because killing too many can lead to the collapse of the ecosystem since they are at the bottom of the food chain.

Another instance is "Stewed Cabbage/Orcs," in which a red dragon's (Tertiary Consumer) presence drives orcs (Secondary Consumers) from their underground villages to raid human settlements on the upper levels. The protagonists initially view taking out the dragon as a purely good act, but Senshi consistently cautions against the unintended consequences of disrupting the natural order. Of primary concern is that each level of monsters keeps the ones below it in check, and that by eliminating any one trophic level, it will cause a surge of monsters to escape the dungeon, thereby terrorizing the populace further. His warnings reinforce the idea that removing too many alpha predators can have potentially harmful effects on the dungeon's delicate balance.

The Ultima Online Cautionary Tale​

A lot of this is just theory; after all, a DM can tweak their world as they see fit. But it has played out in video game ecosystems, most notoriously, the massive multiplayer online role-playing game (MMORPG) Ultima Online. The developers intended to create a dynamic ecosystem with a natural food chain: deer (Primary Consumers) would eat grass (Producers), wolves (Secondary Consumers) would eat deer, and dragons (Tertiary Consumers) would eat wolves. This trophic hierarchy was designed to create a natural flow of resources and creature spawns within the game world. Then adventurers were introduced into the system.

The reality of adventurers (Secondary Consumers) entering the scene quickly collapsed the carefully-crafted system. Player characters, acting as powerful predators themselves, indiscriminately hunted wolves, deer, and rabbits for loot, experience, and resources. There were just too many Secondary Consumers -- and in reality, some of the adventurers as they became powerful enough were Tertiary Consumers -- and they didn't have any inclination to stop. Like hunters depopulating an entire species for pelts, adventurers just did what they did: killed things just because traditionally that's what players did in other MMORPGs to advance in level.

This excessive predation highly unbalanced the system, leading to unnatural population declines. The developers were eventually forced to adjust how creatures fed and thrived to compensate for the players' overwhelming impact.

Bringing Your Dungeon to Life​

For DMs looking to create truly immersive megadungeons, considering the underlying ecology is paramount. By thinking about the food chains, predator-prey relationships, and how the environment sustains its inhabitants, you can craft a dungeon that feels alive and reacts to the players' presence. Similarly, nature-minded PCs might care about this stuff like Senshi does; he frequently admonishes the party's spellcaster to stop obliterating everything on the map out of fear of collapsing the entire ecosystem. Good-aligned PCs who care about the villages above the dungeon may similarly be inclined to try to manage monster resources vs. just wiping out everything that moves.

Just as Delicious in Dungeon illustrates, even adventurers driven by their own needs can become part of this intricate web. And as the Ultima Online example shows, the players themselves can have a profound impact on the dungeon's natural order. So, the next time you're designing a sprawling underground complex, consider taking a page from Senshi's cookbook and give players a reason to think about what the monsters – or the PCs! – eat.
 

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Michael Tresca

Michael Tresca

Don't overlook the impacts that dungeon ecology can have on topside ecology. Real world example would be cave complexes that are home to thousands of bats. The bats eats things topside and then provide food for things inside. Plus sometimes a usable pile of waste for humans needing fertilizer or ingredients for gunpowder.
I didn't touch on it in detail but this is an ongoing concern in "Delicious in Dungeon" In which there's a real worry that if the monster ecosystem collapses, the more powerful things that are kept in check in the lower levels will boil up and wipe out villages (the protagonists say this has happened before). Conversely, when that starts to happen, it usually means there's something REALLY BAD at the bottom that's stirring. The first arc of the series is a red dragon, which drives orcs to the surface. Fascinating stuff.
 

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Creating dungeon ecology can be as real and time consuming as the group wants it. I mean, how many dungeons never include bathrooms, or just throw in a ogyough, oh-my-ga, ogy-bleh to just act as a garbage pit and cube to vacuum up.
There's an entire episode of Delicious in Dungeon that's dedicated to the fact the dungeon has toilets. 🚽 Someone has to clean them. And those toilets are used to fertilize earth golems for harvesting (the golems also serve other purposes, primarily to keep powerful monsters from the lower levels from boiling up). It's both hilarious and not totally unreasonable the more you poke at it.
 


Anime ecology at its finest. I mean it both positively and sarcastically.

1. The dungeon spawns are unlimited, asexual and held in check by higher level consumers.

2. The adventurers are unaccountable or outside of the dungeon system, and thus break it by merely fulfilling their role.

Realistic in-game ecology in a world with such a long history would either adapt to the presence of adventurers or fall apart as soon as a few adventures advanced to higher levels.

The adaptation of dungeon eco-system would probably take one of the following forms:

1. Ultimate spawning sponsor that is not a part of ecology, that is a source of replenishing dungeon staff. Examples: daemonic nation of a remote realm, warping and corrupting wild magic, terminator manufactoring factory, living dungeons that replenish their internal flora and fauna. Adventurers are soldiers in neverending war of attrition.

2. Dungeons as fiefdoms of apex beings. The apex beings, like overlords, rarely participate, but can organize their resources. Adventurers are tolerated up to certain level of interference. Above that, however, they are either captured, compromised or killed.

3. Ultravast urban sprawls or interconnected dungeons. As soon as the adventurers affects spawns of a particular kind of a consumer species, other members of the species arrive to settle, probably with some mercenaries to protect them during initial period of settlement. See Blame.

4. Hungry non-sentients with unlimited spawn potentials. Usually with some cursed rules that limit adventurer ability to engage or damage the ecosystem. See Made in the Abyss.

5. Living dungeons. Dungeons are creatures. If they are depleted of their internals, they eat cities to replenish themselves. If they are left alone, their inner creatures spill out. See 13th Age Living Dungeons.
 

Anime ecology at its finest. I mean it both positively and sarcastically.

1. The dungeon spawns are unlimited, asexual and held in check by higher level consumers.

2. The adventurers are unaccountable or outside of the dungeon system, and thus break it by merely fulfilling their role.

Realistic in-game ecology in a world with such a long history would either adapt to the presence of adventurers or fall apart as soon as a few adventures advanced to higher levels.

The adaptation of dungeon eco-system would probably take one of the following forms:

1. Ultimate spawning sponsor that is not a part of ecology, that is a source of replenishing dungeon staff. Examples: daemonic nation of a remote realm, warping and corrupting wild magic, terminator manufactoring factory, living dungeons that replenish their internal flora and fauna. Adventurers are soldiers in neverending war of attrition.

2. Dungeons as fiefdoms of apex beings. The apex beings, like overlords, rarely participate, but can organize their resources. Adventurers are tolerated up to certain level of interference. Above that, however, they are either captured, compromised or killed.

3. Ultravast urban sprawls or interconnected dungeons. As soon as the adventurers affects spawns of a particular kind of a consumer species, other members of the species arrive to settle, probably with some mercenaries to protect them during initial period of settlement. See Blame.

4. Hungry non-sentients with unlimited spawn potentials. Usually with some cursed rules that limit adventurer ability to engage or damage the ecosystem. See Made in the Abyss.

5. Living dungeons. Dungeons are creatures. If they are depleted of their internals, they eat cities to replenish themselves. If they are left alone, their inner creatures spill out. See 13th Age Living Dungeons.
You could also have a stable natural dungeon ecology that only had to deal with pesky adventures once every generation or so. They l idea that there are hundreds or even thousands of adventurers running around raiding dungeons is a very foreign concept in the D&D games I’ve played
 

I go for small, lair-like dungeons that are part of the surface ecosystem, rather than dungeons that are deep and isolated enough to form their own ecosystems. But if I did do a mega-dungeon, it would probably feature:
  • Perpetual motion photosynthesis, with glowing moss producing its own light to grow by and thumbing its biochemical nose at the laws of thermodynamics.
  • A don't-need-to-eat magic field, produced either by that magic moss or by something else. The monsters don't need to eat for calories, but instead only need to eat small quantities for certain essential nutrients. Thus they only eat very small amounts of each other, along with occasional delicacies like human, elf, dwarf, and halfling, and poop and piss very little as well. (They might have a meal once a month, or once a year, or even less often. Which is why they're hungry: They want food much much more than they actually need it.)
  • Adventurers and other outsiders don't benefit from the don't-need-to-eat magic field unless they become warped into being dungeon inhabitants.
  • The monsters are thus all "primary consumers," in a way analogous to surface critters being "primary consumers" of oxygen produced by plants. But they're also nearly all "secondary consumers" or "tertary consumers" of those rare and special nutrients.
  • Most of the creatures will have originated in lower planes. They, or their ancestors, first appear in the bottom level of the dungeon. As time passes they become weaker and more degenerate, and are pushed up to the higher levels by the stronger competition. So the goblins and kobolds of the top ("first") level will have been pit fiends, or will have had pit fiend ancestors, long ago, but will have so degenerated that their fiendish traits are reduced to inactive, difficult to detect traces.
 

Megadungeons, long a staple of D&D, can be just as complex as any other ecosystem in your campaign.

View attachment 405431
Picture by Thompsma - Own work, CC BY 3.0, File:TrophicWeb.jpg - Wikimedia Commons

The concept of megadungeons conjures images of sprawling underground complexes filled with untold riches and deadly monsters. But beyond the treasure and encounters lies a deeper level of worldbuilding: its ecology. Considering the intricate web of life can transform a static dungeon crawl into a living campaign. But to make that ecosystem matter to the PCs requires some planning that can make simply killing a monster change the course of the game.

Dungeon Ecology Basics​

For a dungeon ecology to truly resonate with PCs, certain elements need to be in place (see Lew's article on the same subject). Firstly, the dungeon needs to be large enough and have multiple levels to support a diverse ecosystem (Megan Wiseman calls this "Gygaxian Naturalism" after co-creator of Dungeons & Dragons, Gary Gyax). Different levels with varying resources and environments can host distinct food chains and monster populations. A small, linear dungeon simply won't have the space for a complex web of life.

Secondly, repeated visits to the dungeon are key. If the PCs are delving into the same complex over multiple sessions, they're more likely to observe patterns, note changes, and perhaps even develop a sense of how the dungeon "works." Why bother learning what eats what if you're only planning a one-time raid?

Finally, the possibility of PC impact on the ecosystem should be apparent. If the adventurers' actions – whether through hunting, introducing new creatures, or altering the environment – have noticeable consequences, they will be more invested in understanding and perhaps even manipulating the dungeon's natural order.

The basics of ecology involve trophic levels, each with its own level in a food web:
  • Level 0 (Decomposers): Often left off food webs, these involve creatures responsible for breaking down nutrients like slimes, carrion crawlers, and fungi monsters like gas spores and myconids.
  • Level 1 (Producers): Plants and algae make their own food. These include plant monsters like shambling mounds and twig blights.
  • Level 2 (Primary Consumers): Herbivores eat plants. Curiously, there are not a lot of these types of monsters in core D&D. Giant boars, goats, and lizards might qualify.
  • Level 3 (Secondary Consumers): Carnivores that eat herbivores. There predators aplenty, and this is where a lot of humanoid monsters can be found, from kobolds and goblins up to orcs and hobgoblins.
  • Level 4 (Tertiary Consumers): Carnivores that eat other carnivores. The most dangerous of these are apex predators, who have no predators. These are monsters that can challenge entire parties, like dragons and krakens.
Food webs can be incredibly complex, but for a game master's purposes even a simple pyramid can help sketch out what creatures depend on others and the impact of their removal.

An Adventurer's Guide to Subterranean Sustenance​

The anime series Delicious in Dungeon offers a humorous look at a dungeon with an internally consistent ecology. The protagonists frequently consider the ecological implications of their actions, driven by their need to eat the monsters to survive.

A prime example is the episode, "Kelpie/Porridge/Broiled with Sauce." The adventurers observe that a kraken (Tertiary Consumer) has become so successful at hunting the dungeon's mid-level monsters that their populations are dwindling. This leads to fewer food sources for other creatures, highlighting how the removal of too many mid-level prey can negatively impact the entire ecosystem. Similarly, Senshi the culinary dwarf advises the party's spellcaster Marcille to not just blast the flying bladefish (Primary Consumers), because killing too many can lead to the collapse of the ecosystem since they are at the bottom of the food chain.

Another instance is "Stewed Cabbage/Orcs," in which a red dragon's (Tertiary Consumer) presence drives orcs (Secondary Consumers) from their underground villages to raid human settlements on the upper levels. The protagonists initially view taking out the dragon as a purely good act, but Senshi consistently cautions against the unintended consequences of disrupting the natural order. Of primary concern is that each level of monsters keeps the ones below it in check, and that by eliminating any one trophic level, it will cause a surge of monsters to escape the dungeon, thereby terrorizing the populace further. His warnings reinforce the idea that removing too many alpha predators can have potentially harmful effects on the dungeon's delicate balance.

The Ultima Online Cautionary Tale​

A lot of this is just theory; after all, a DM can tweak their world as they see fit. But it has played out in video game ecosystems, most notoriously, the massive multiplayer online role-playing game (MMORPG) Ultima Online. The developers intended to create a dynamic ecosystem with a natural food chain: deer (Primary Consumers) would eat grass (Producers), wolves (Secondary Consumers) would eat deer, and dragons (Tertiary Consumers) would eat wolves. This trophic hierarchy was designed to create a natural flow of resources and creature spawns within the game world. Then adventurers were introduced into the system.

The reality of adventurers (Secondary Consumers) entering the scene quickly collapsed the carefully-crafted system. Player characters, acting as powerful predators themselves, indiscriminately hunted wolves, deer, and rabbits for loot, experience, and resources. There were just too many Secondary Consumers -- and in reality, some of the adventurers as they became powerful enough were Tertiary Consumers -- and they didn't have any inclination to stop. Like hunters depopulating an entire species for pelts, adventurers just did what they did: killed things just because traditionally that's what players did in other MMORPGs to advance in level.

This excessive predation highly unbalanced the system, leading to unnatural population declines. The developers were eventually forced to adjust how creatures fed and thrived to compensate for the players' overwhelming impact.

Bringing Your Dungeon to Life​

For DMs looking to create truly immersive megadungeons, considering the underlying ecology is paramount. By thinking about the food chains, predator-prey relationships, and how the environment sustains its inhabitants, you can craft a dungeon that feels alive and reacts to the players' presence. Similarly, nature-minded PCs might care about this stuff like Senshi does; he frequently admonishes the party's spellcaster to stop obliterating everything on the map out of fear of collapsing the entire ecosystem. Good-aligned PCs who care about the villages above the dungeon may similarly be inclined to try to manage monster resources vs. just wiping out everything that moves.

Just as Delicious in Dungeon illustrates, even adventurers driven by their own needs can become part of this intricate web. And as the Ultima Online example shows, the players themselves can have a profound impact on the dungeon's natural order. So, the next time you're designing a sprawling underground complex, consider taking a page from Senshi's cookbook and give players a reason to think about what the monsters – or the PCs! – eat.
Well this is delightful, and not just because I dearly love Delicious in Dungeon. I've been interested in putting more ecological work into my megadungeon campaign for a while now. Lots to think about!
 

Wise words: "The lesson of the virtuale ecology was to us that testing the game in house is an entirely inadequate test in contrast to the reality of being in the hands of players. Not only are players going to face &think about the experience differently than we do in house but by sheer numbers they will crush or test things in a very different way"

I remember hearing about UO back in the day and immediately thinking about the obvious problems online gaming had displayed by then∆, it's good to hear about how they recognized and tried to address some of them but also realized sometimes intended design can't work in the wild and did what they could to replace it with needed design. Sometimes it seems like there is a trend in modern gaming (ttrpgs especially) for designers/publishers to state the intended results of a design that worked in closed door play and blame anyone who has a bone to pick with the results in actual real world play rather than doing anything about the merits of that bone itself.


∆ UO was starting to compete with EverQuest by then or would soon. That's not a slight against UO though... It nearly predated widespread consumer Internet and very much kicked off online gaming in a format other than text based MUDs. They were building the racecar while the track it worse on was still being paved
Too bad needed design is so often far less interesting and creative than intended design. Stuff like the UO story just makes me sad.
 

The real problem with the UO situation, from the ecological point of view, is they didn't limit the number of adventurers by starvation. If the adventurers wiped out the rabbits, deer, and wolves, they should have eventually been forced to become vegetarians and then their numbers would probably have been limited as they deforested the dungeon and then starved to death.

Of course, if they'd done that, they would have lost money and angered players.

Wouldn't be the first time economics has conflicted with ecology. ;)

People have some great ideas here! The only thing I have to add is you have to figure out what's standing in for sunlight, which is the ultimate source of free energy for almost all terrestrial ecosystems. No reason the plant-equivalents can't be magic-eaters (thaumovores), or live on chemicals the way tube worms (technically, their bacterial symbionts) at the bottom of the ocean do. Real-life caves usually get rainwater, debris, or animal dropping that wash in. There are occasional lithoautotrophic bacteria that can oxidize and 'eat' rocks through extracellular electron transfer.

Of course, no reason you have to be this 'realistic' with your fantasy world!
 

In one of my dungeons, the fungi and oozes tap into the inner planes for energy and matter to grow without sunlight. Then cave critter eat them. Then monster eat the critters.
 

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