Tips to Create Better & More Believable Fantasy & Science Fiction Species


Whether you're looking to create aliens to fill your space opera galaxy with, or trying to figure out what kind of subspecies of orks you need, or trying to develop an SF world from the ground up, here are some things to keep in mind when creating science fiction and fantasy creatures.

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Remember, you’re creating creatures for your world, not someone else’s.

If the first thing going through your mind is “I want it to be like X book I’ve read because that book was awesome!” stop. Think about what made that book enjoyable to you. Some of the most enjoyable books are enjoyed because they brought you something you had never seen before, not because they repeated what another writer had already done.

Rather than borrowing someone else’s finished SF species to use as a template, start with a blank slate and add things on as they make sense in the context of your world, not as you think they would be cool to have. Alternatively, if something strikes you as cool to have, stop and ask yourself whether it makes sense in the context of your world, or whether it needs adjusted or modified to fit, or whether it doesn’t make any sense at all and should be discarded entirely.

For example, if I’m trying to create a world where my elves are A: inspired by actual myths and legends, and B: more or less supposed to follow laws and principles of real-life biology, then there’s no sense in shoehorning other peoples’ elf races (eg, night elves, dark elves, moon elves, etc) into my world - I’m making my world, not theirs. This means that not only can things be different, but they also should - the tone and style I’m trying to set will always trump what anyone else thinks “should” be in a fantasy or sci-fi world.


Give your creature the right equipment for the job it’s supposed to do, and let your creature use its equipment right.

Some people want their fantasy creatures to behave in a certain way, and so they give them these behaviors - failing to check whether the behaviors even make sense given the biological tools and body plan of the creature in question.

For example, in a lot of popular fiction, vampires are depicted as using their fangs as primary weapons much as a big cat would - they pounce their victims or enemies and take a strategically-placed chomp and once they do that, the fight’s pretty much over. In reality, this would be a horrible strategy for most vampires, especially in combat with anything of equivalent physical strength, or even anything that would realistically flail and scream. Big cats have huge mouths and fangs, and their bodies are shaped in such a way that their momentum is well-focused on their heads when they attack. But most vampires follow the basic human body template, and the human mouth is pathetically tiny in comparison while the shape of the human body does not lend well to putting force into the mouth and bite. Unless your vampires also have secondary shapeshifting powers to make their mouths a whole lot bigger and positioned better, their fangs shouldn’t even come into play until the victim is already subdued, or as a last resort against a convenient target in a grapple. Deliberately putting your entire face into an enemy that’s fighting back at the same time doesn’t do so well for your situational awareness.

The primary weapons of the human body are the hands and feet - which means that any vampire with a lick of sense would do something like… oh, up and kick the pouncer’s pretty pointy teeth in.

Remember, real-life creatures have the behaviors they do for a reason. While giving humanoid creatures unhumanish behaviors can be a great way to invoke the uncanny valley effect or make them seem more alien, you also need to ask yourself if the behavior would actually help or hinder with the body plan the creature has.



Everything about your creature’s physiology should exist for a reason.

In the real world, no feature or body part exists without a reason. Everything either serves a purpose, or is a vestigial remnant of something that served a purpose for its ancestors.

In a world where creatures lack eyes, features such as camouflage or warning colors would have no reason to develop in the first place. If peafowl were sightless, peacocks would not have their magnificent tail feathers because there would be no point - they serve as a visual cue to the peahens that the peacock is a healthy and fit mating specimen. A creature that doesn’t or never lactated to feed its young would have no reason to have teats.

And remember - creatures don’t evolve to handle hypothetical scenarios; they evolve to handle ones that already exist. Evolution is driven by natural selection, which is to say that those that are best-suited to the environment are the most likely to produce the next generation.

For example, let’s say we have some sort of rodent that feeds primarily on beetles, and most beetles around hide down in small rocky spots. If the smallest rodents are the most capable of finding these beetles because they can fit into places that larger ones cannot, then the smaller ones will survive to produce small offspring, and thus natural selection will select for smallness. But if circumstances change - say, a new non-burrowing species of beetle moves in while dropping temperatures make the area inhospitable for burrowing beetles - then large rodents might be selected for if their larger bodies keep them from losing heat as quickly as their smaller relatives and/or make it easier to catch non-burrowing beetles. And just as easily, the environment could go back to favoring the smaller rodents. The advantage of one generation can be the undoing of another.

(And just a quick note - creatures do not have to die from unnatural causes or starvation to be removed from the gene pool; all they simply have to do is fail to breed before they die. Also, in eusocial and semi-eusocial organisms, having non-breeders can be an advantage, as they can contribute to the survival of the group as a whole without worrying about tending its own offspring.)


Ask yourself what environmental and ecological impacts your creature would have in the world around it.

As detailed in Common Plotholes In Vampire Fiction, people often don’t really consider the realistic impacts that their SF creatures would have on the world around them. To summarize, the volume of animals and/or people killed by vampires in works such as Twilight and The Vampire Chronicles would have a significant impact on the world, but neither of these works acknowledge or address this.

Fantasy writers often throw in huge dragons without regard to the fact that we’re dealing with enormous apex predators. If anything, the existence of giant dragons would demand the need for giant prey. If you’re putting huge dragons into your world, does your world have the kind of prey it would take to support them?

Christopher Paolini unwittingly doomed many of his dragons to very cruel fates in Eragon when he declared that dragons were immortal and they never stop growing. If this were true, the dragons would require ever-increasing amounts of food until it became impossible to feed them - and the dragon would then have to either starve to death or be put down to keep it from eating everybody’s livestock and/or completely destroying the ecology.

Also, a rule of thumb in biology is that when two species that fill the same ecological niche live in the same area, the fitter species will eventually outcompete the other for resources, which means that the other will go extinct or adapt to fill a different niche. So, let’s say that you have dragons as a successful apex predator in your world. To make them fit into your world, you have to pick one of the following scenarios:

The same rule goes for humanoid species, too - if humans and elves essentially fill the same ecological niche and have to compete for resources, then one or the other is eventually going to lose out.


Keep in mind: If there was ever a “perfect” lifeform, it probably wouldn’t be what you think it would be.

Many people, when thinking of “perfect” or “superior” organisms, tend to think in terms of “something that could easily kill a human in a one-on-one unarmed fight” or “easily able to destroy human civilization without breaking a sweat.” In reality, physical might and combat ability are only one of any number of potential factors that factor into how fit an organism actually is.

First, it’s not about the survival of the individual - it’s about the survival of the species. A tiger might be able to easily defeat a single unarmed human in a one-on-one fight, but when humans are in their natural state - banded together and armed with tools of their own devising - tigers quickly wash out. Compare with the “vermin” animals - rats, mice, cockroaches, etc. These creatures haven’t simply survived humans invading their habitats and trying to kill them - they’ve thrived. Thus, vermin are actually much closer to “perfect” than tigers!

A vampire species that subsists on human blood would not be “superior” to humans, even if they were stronger, faster, etc. While said vampire is an apex predator that preys on humans, they would never be able to supplant humans or fill their ecological niche - in fact, without humans, they’d go extinct. A kaiju-type species that only reproduces every thousand years wouldn’t be superior to humans if humans were able to gang up on it and take it down, then basically wipe out the species in a series of relative zerg swarms on the kaiju critters.

Hypothetically, a “perfect” lifeform would be one that is already capable of handling every possible situation or scenario that could ever possibly exist, up to and including habitat invasion or destruction from other species (including humans). And in the real world, that isn’t too likely, especially since the tradeoffs a species makes that enables it to survive one scenario (eg, evolving flippers from legs to swim better) can make it more difficult to survive a different one (eg, a lack of water to swim in).

In the end, a species’ ability to successfully replicate and avoid extinction is the only measure of how successful or “superior” that species is.


If you liked this, you might also be interested in:

Fantasy & Science Fiction Creature Development Questions
Things Writers Should Know About Animal Behavior
Tricks & Tips For Creating Fantasy, Sci-Fi, & Other SF Names
Basic Tips To Create More Believable Sci-Fi & Fantasy Religions & Belief Systems

Tips & Ideas To Create More Believable Sword 'n Sorcery Worlds
Tips To Write & Create Better & More Believable Futures
Things Your Fantasy Or Science Fiction Story Needs

Things You Need To Do In Your Science Fiction Or Fantasy Story
Spaceships, Airships, & Other Fantastic Crafts: Things To Think Out & Consider
Creating Plausibly Functional & Useful Tools, Gadgets, & Weapons For Fiction

External Resources

Evolution: 24 Myths And Misconceptions
Understanding Evolution @ Berkeley University
How To Create A Scientifically Plausible Alien Lifeform
The Desert Adaptations of Birds & Mammals
Antarctic Animal Adaptations
Winter Adaptations Of Animals
Rainforest Animal Adaptations



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