Diagram of a six-legged animal with a thick tale and pointed beak.

Every world needs animals to give the setting life. I’ll focus on creating realistic and semi-realistic creatures and aliens, but these techniques can also be used to create races, plants, and other organisms. As an ongoing example, we’ll be making a creature as we go. Let’s get started.

1. Find a Niche

A niche is the role an organism takes in its environment. Every animal has a niche that it fills, and all animals have traits that help them perform in their niches. Deciding on a niche before starting on the animal results in a more realistic creature, similar but distinct from nature’s own “designs.” Always keep the intended niche in mind when creating your creatures, but don’t be afraid to stray from it slightly – animals in real life sometimes have vestigial traits that come from their ancestors.

If you’re having trouble coming up with ideas for your creature, take inspiration from real animals, living and extinct. Cambrian life is particularly alien and can be good inspiration for more surreal creatures.

For our example creature, let’s make a tree-dwelling herbivore that lives in temperate forests. There isn’t anything we can do with this right now, but we’ll keep it in mind during the rest of the creation process.

2. Pick a Body Type

This is the very basic shape of your creature, the framework to build upon. Body type and niche are not very dependent on each other, and most body types can fit in any niche with a bit of creativity. Pick a body type you like or already have ideas for.

A chart showing body shapes of different creatures, both real and fictional.

Keep in mind that this is not an exhaustive list of body types, and that a creature’s actual body can vary significantly from the basic body type. Birds, whales, and snakes were all at one time quadrupeds, and except the birds, all have lost some, or all, of their limbs.

Our example creature will be hexapedal because it is a nice shape – not too alien, but not too familiar either. It is well suited for a land-based creature, unlike types such as cnidarian or rotifer.

Don’t include too many different body types in a single world; it will make the world feel less cohesive. Stick to five or fewer for the majority of your creatures as well as a few minor ones.

3. Outline the Broad Strokes

This step makes the creature your own. Add large details about the creature, such as the body’s actual shape and how it interacts with the world. The niche you decided on at the beginning is now important; nothing you add in this step should contradict the creature’s role in its environment. It can be helpful to research real animals that have a similar niche to find out what adaptations they have for their environments. However, don’t worry about your creature fitting perfectly into its niche yet – that’s in a later step.

To fill in more details about your creature, ask yourself questions about it. Does it have eyes? If so, what do they look like? Does it have a skeleton or exoskeleton? How does it breathe? Having a second or third pair of eyes on your work is a great way to catch things you may have forgotten.

Our example creature has an internal skeleton, a tail, and bird-like feet. It will pierce plants and drink their sap with a hard, tubular mouth.

4. Visualize Your Creature

A detailed picture isn’t necessary at this step since the creature isn’t complete yet. A simple sketch will do. This can help you see issues with the design, pick the traits you like the look of, and use the sketch as a reference for other creatures you make (more on that later).

Diagram of a six-legged animal with a thick tale and pointed beak.

Here is a sketch of our example creature. I’ve drawn birdlike feet, reptilian eyes to see with, and antennae that can detect scent and air vibrations. It will drink sap with its tubular mouth, while it uses openings on its neck to breathe. The long reptilian tail and crest on its head make it more interesting. Notice that these traits are still not very specific. This is because we are creating a  generic version of our final creature; the remaining details have yet to be added.

5. Fill In the Details

Now you’ll finish tailoring your creature to the niche you decided on at the beginning. Look over what you have and make minor changes: the shape of the eyes, the length of the legs, etc. Give it some colors – for camouflage or otherwise.

Our example creature looks like it could fit its niche well already, but there’s more we can do. Let’s make its tail prehensile, like a chameleon’s, and lengthen the waist to make it easier to curve around large branches. Since it may get a bit cold in the winters, let’s give the creature a thin-downy coat. The legs are fine; the front feet are shaped like a songbird’s, letting it grip branches, while the back feet aren’t. Let’s give it some claws on the hind legs to hold onto the bark and camouflage it in an unassuming brown with hints of green.

Six legged creature in tree, with tail wrapped around a branch and snout sucking through the tree bark

Here is our finalized creature. It’s not as important to draw this as it was to visualize the broad strokes, but it has the same benefits.

6. Develop the Family

Congratulations, your creature is complete! But evolution isn’t a straight line; it branches. You can use this to your advantage, turning your creature from step four into a template to make as many variations as you want. Having related creatures will make your world feel more cohesive, and this is far easier than creating one from scratch every time. Creating related creatures for different environments is simple, just repeat step five with a different niche in mind.

Let’s make a relative of our example creature that’s adapted to living in deserts. This creature will drink water stored in cacti and eat their sap. As an adaptation, it will be thinner than its forest counterpart, letting it release heat more efficiently. Its crest will be larger as well and full of blood vessels, allowing it to control its temperature like the extinct Dimetrodon did with its sail. It will lose the downy coat and have a simpler, straighter tail. Since it will not need its back toes, they will be reduced to small spurs. The desert creature will be sandy brown, instead of the dark brown of its relative.

A scaly six legged creature.

You can take this a step further and create distant relatives to your creatures. Make ones that are a “missing link” between two others, or make a chimpanzee equivalent for one of your races. Now that you have a starting point, populating your world with fantastical creatures is easy.

This article was adapted from Issue Three of Worldbuilding Magazine, your go-to tool for all things worldbuilding.

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