Many RPG worlds seem to have a fauna and flora that is composed of the organisms found in our world with a more or less well thought out set of monsters added on.

I was wondering how to design a believable ecology suitable for a fantasy RPG world spanning a small continent with earth like conditions (large enough to have several different biomes, for example warm deserts, mountains, plains, temperate forests and taiga, the exact biomes are not that important).

I want the ecology to contain a subset of earth organisms as well as non earth organisms, some of which should be considered monsters.

How can I define such an ecology that appears to have evolved through evolution under the following constraints.

  • Definition should fit in limited space, maybe about 50 book pages of easy to read text (should fit in an RPG book along other world information and rules)
  • Only defining details that seems important to the human inhabitants (no need to include bacteria for example)
  • The definition should show how the "food pyramid" works and avoid mysteries such that how some creatures would find something to eat given their habitat or other aspect of their definition
  • The non earth organisms should in some way fit into the tree of life (but maybe a modified one for organisms that evolved to use magic to function)
  • Habitats for organisms should be defined, on some resolution, maybe by climate zone in some cases and in great detail in others if that seems important
  • The definition should include which organisms are deemed valuable, both wild and domesticated, and which is considered problems
  • The earth organisms should not vastly outnumber non earth organisms in any ecological niche
  • The whole thing should feel like it fits together not just a bunch of creatures bolted on an existing ecology

Hopefully the question is understandable, I am not interested in a specific instance of ecology but rather how to design an ecology for such a world in a way that looks like it fits together without going into excessive detail such that it becomes an project that is impossible to complete (or that no one bothers to read).

A final point to specify, I am mainly interested in answers that uses no magic to solve problems, if it was not a fantasy world I would have tagged it with hard-science.

  • 1
    $\begingroup$ How do actually put things into words is more a matter for the Writing SE, not for us. We can however help you figure out how your world should work, the interactions between various types of creatures, etc. Compare what is on topic for Worldbuilding SE and what is on topic for Writers SE. $\endgroup$
    – user
    Commented Jul 7, 2016 at 9:25
  • $\begingroup$ How is this question about “putting things into words?” it is about “how to design a believable ecology suitable for a fantasy RPG”. It looks like we do not understand the “I am […] interested in […] how to describe” the same way. :) $\endgroup$ Commented Jul 7, 2016 at 9:27
  • $\begingroup$ @MichaelGrünewald The question title says quite clearly "How to describe". The question body asks "How do I best describe ... such an ecology" and specifically states that OP is "not interested in a specific instance of ecology but rather how to describe an ecology for such a world". The word "describe" occurs four times in the question (including the title), "design" only once. If we are reading this that differently, then the question is obviously unclear. In either case, it should be put on hold until the issues can be worked out (if possible). $\endgroup$
    – user
    Commented Jul 7, 2016 at 9:59
  • $\begingroup$ The author of the question took care of writing “How do I best describe (as in how do I structure it and what to focus on)” so the question is clear enough, IMHO. $\endgroup$ Commented Jul 7, 2016 at 11:08
  • $\begingroup$ Welcome to the site, lijat. I have to agree with Michael on this one. We'd be more than happy to help with aspects of your ecology that you have questions about, but document layout and topics of concern aren't part of our scope. $\endgroup$
    – Frostfyre
    Commented Jul 7, 2016 at 12:11

3 Answers 3


Building a complete ecology is quite a problem in itself, so I will be approaching this from the presentation standpoint.

To start, I would look at historic examples of bestiaries such as the Aberdeen Bestiary. You don't specify the type of fantasy, but assuming it's the classic Medieval European style, you may choose to emulate some of the artistic aspects of these creations. More relevant to the discussion here though is the content of the bestiaries. Rather than a scientific breakdown of the natural order, they provide seemingly incidental facts. Here is one passage from the Aberdeen Bestiary:

Of the panther

There is an animal called the panther, multi-coloured, very beautiful and extremely gentle. Physiologus says of it, that it has only the dragon as an enemy. When it has fed and is full, it hides in its den and sleeps. After three days it awakes from its sleep and gives a great roar, and from its mouth comes a very sweet odour, as if it were a mixture of every perfume. When other animals hear its voice, they follow wherever it goes, because of the sweetness of its scent. Only the dragon, hearing its voice, is seized by fear and flees into the caves beneath the earth. There, unable to bear the scent, it grows numbed within itself and remains motionless, as if dead.


The panther is a beast dabbed all over with very small circular spots, so that it is distinquished by its black and white colouring with eye-shaped circles of yellow.

The bestiary presents information about many creatures that the reader should be familiar with (an entire section on livestock for example), as well as some more exotic creatures such as the panther. Obviously, the lesser known items are more fanciful. One can imagine the author writing these passages based off of some traveler's account. With this in mind, we can break down the facts presented about these creatures into several categories:

  • Visual appearance
  • Relevance to the reader
  • Interaction with other creatures and its environment
  • Some story about the creature

Now let's apply this to your own fantasy realm. I imagine you have some idea of the types of creatures you wish your players to encounter. Pick out certain details about these creatures, thing that a traveler in your world would find relevant or interesting or perhaps something that ties into your game. Then piece them together into a description. You shouldn't worry about being too vague or inaccurate here about some of the more exotic creatures, as that simply adds to the mystery. Your players most likely do not care for the intricate details of the ecosystem, merely the overview of the creatures and their features, so that's what you should present. Here's an example I came up with:

The Snow Dragon

The snow dragon is a magnificent beast that makes its lair in the Frozen Mountains. The snow dragon is as pale as the snow peaks themselves, with breath as cold as an arctic gale. Its wings are nearly a hundred cubits from claw to claw. The Onari tribe holds this beast sacred, and has a great shrine dedicated to it. The beast is particularly fond of preying on the goats which also reside in the mountains. These goats are offered to the beast during the Onari harvest festival. Travelers should be warned not to wear furs when traveling through the mountains, as the snow dragon has been known to attack those it mistakes for prey.


To supply food for an increased amount of predatory species (ie monsters), you will need to have some areas of super fertility to allow for an increased amount of prey. You could simply increase the overall fertility, but it may be more "realistic" to limit it to more localized spots.

Perhaps the banks of Azure River, with its source of the Fountains of Life on the flanks of the Greenspire Mountain, is especially rich in grasses, vines, fruit trees, and mushrooms, which feeds large amounts of rodents, rabbits, birds, swine, primates, and a smaller amount of deer, elk, and moose.

Perhaps the Creeping Vales is a landscape of rocky spires and outcrops that a covered in a Kudzu-like vine with succulent leaves and seedpods and that grows at an astonishingly fast rate. Large grazers can wander into the area, eat their fill and leave. Smaller herbivores might find themselves trapped by the vines if they stop moving for almost any length of time.

Examples like these would allow most of the world to be earth-like while giving a source of food to the monsters, especially ones that can easily travel far, such as a flying dragon, for instance.


Use the wolf-prey model to describe your ecology.

Wolves usually ignore lone animals.

Wolves usually attack only weak animals that would die soon anyway.

Wolves feed on the more overpopulated animals, cause their overpopulation could destroy the entire ecosystem and nothing would survive.

Wolves unlike birds or humans hunt only what is needed to survive not what tastes better.


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