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Scariest Science Fiction Aliens

The scariest science fiction aliens remind us that, when we look back, some horror might be peering right back at us.

By Anthony GramugliaPublished 6 years ago 15 min read

The scariest science fiction aliens often capture some element of existential dread we all hold inside. Good horror fiction captures that spark of terror all of us have inside from the days of cave man. The fear of being eaten. The fear of what lurks in the dark – and what darkness is more vast and mysterious than the dark expanse of space?

The scariest science fiction aliens remind us that, when we look back, some horror might be peering right back at us.

The Borg (Star Trek)

In a progressively more and more computerized civilization, a logical fear that many scientists may have is the fear that, one day, computers may be so infused in the human lifestyle that we become computers. Or, at the very least, computerized.

Enter the Borg. The Borg is a collective of interconnected bio-mechanical interfaces. Their mission: assimilate.

They even coined the phrase, "Resistance is futile."

Admittedly, as time passes, the Borg become less and less frightening. After all, there are so many times you can blow a Borg cube out of the sky before they stop being scary. Still, there's something very horrifying about an alien race taking over your personality, eradicating all traces of your former humanity, until there is nothing left.

And in their early appearances on Star Trek: The Next Generation, the Borg were quite terrifying.

The episode named "The Best of Both Worlds" left countless Star Trek fans in awe and horror as Captain Picard himself was consumed by the Borg. If Picard could be assimilated, what hope did anyone else have? (Fans know he gets better, but still, at the time nobody knew that.)

Maybe not the scariest science fiction alien, but the Borg are certainly big contenders.

Worms (Slither)

Fewer things are grosser than slugs. Slugs are just nasty little things, but James Gunn (who would later go on to direct Marvel's Guardians of the Galaxy films) way, way worse for us.

When Grant (Michael Rooker) pokes a space rock he finds in the woods, he accidentally causes himself to get infected with a bunch of space slugs. The slugs continue to infect others and overtake an entire town, making everyone a grotesque part of the same hive mind.

Aside from just being gross, what makes the aliens from Slither among the scariest science fiction aliens around is how the aliens perverse the sanctity of the body. Slither is, in essence, a body horror movie, one that disturbs by perverting and distorting the human form in horrific, vile, and just plain gross ways.

The Body Snatchers (The Invasion of the Body Snatchers)

What if tomorrow you woke up, and you weren't you? You were someone else. Replaced.

Welcome to the world of The Invasion of the Body Snatchers. Drawing from the Cold War paranoia that had swept America during the 50s, the film introduced audiences to the Body Snatchers – alien pods that kill people in their sleep, and replace them with identical copies.

Identical looking, anyway.

They look like the originals, but don't act like them. They are all part of a hive mind that exist only for one purpose: spread.

In both the original film and 70s remake, the pods exist as a haunting metaphor for the hive mind mentality. Whether you were blindly falling into the Communist agenda or submitting to McCarthy's mad paranoia, you lost all semblance of your former self as the ideologies overtook you.

That's one of the reactions why the Body Snatchers rank as some of the scariest science fiction aliens. They represent the loss of individuality.

And I would be remiss to forget the final scene of the remake – a movie moment so bone chilling that, for many, it ranks as one of the scariest moments in sci-fi horror film history.

Necromorphs (Dead Space)

Yes, I know. Necromorphs are a video game villain. The Necromorphs from Dead Space may not be considered works from sci-fi canon like, say, the Xenomorphs or Borg, but they remain among the scariest science fiction aliens around.

Necromorphs are in essence an alien corruption that overtakes existing biomasses, and mutates them into something grotesque. Every chunk of the body is sentient. You can't shoot them dead. Your only hope is to chop them into enough pieces so that every individual chunks is rendered harmless.

They function like an alien virus – but, once that latches on, you are doomed. If they sound familiar, you might remember an alien race that will be mentioned later on in this list.

The Shadows (Babylon 5)

Babylon 5 remains one of the greatest shows to ever hit television. Among the numerous aliens the show introduced, the most frightening remain the Shadows.

The Shadows are in every sense of the word alien. They are an incorporeal race of entities that have waged war on the rest of the universe for millions of years. However, don't take their bizarre appearances as a sign that they are just crazy animals. The Shadows are intelligent.

And that intelligence makes them scary.

It's one thing if a creature is pure chaotic destruction, there to destroy and ruin and little else. The Shadows, though, bring about the ruination of civilizations through secret agendas and schemes. Most notably, they utilized a bioengineered virus to kill off entire planets.

Unlike most of the scariest science fiction aliens around, however, we don't even know what the Shadows really look like. Or what their names are. Everything about them is hidden behind lies and disguises. The only thing we really know for sure about these creatures is that they want us dead.

And that they're good at making us dead.

The Color Out of Space (The Color Out of Space)

Art By Marcus Crassus

Of all of H.P. Lovecraft's creations, few are as terrifying as a sentient color carried to a Massachusetts town inside a meteor. It's hard to categorize this enigmatic color as a living creature. After all, it's just that: a color. It doesn't have mass or anything like that.

Yes whatever the color touches starts to rot. It corrodes the soil, and all that grows from it becomes... wrong. No other words for it. Whatever eats the wrong growths becomes wrong themselves. And don't drink any of the water the color touches, either, because you'll end up wrong too.

A rotten, bloated, crumbling mess. You'll rot before you die, and the rot will be so foul that even the bugs feasting on your decaying remains will start rotting on your hide.

We have no idea where the Color came from or what worlds it has left to ruin. The unanswered questions force us to remember that space is a hostile expanse from which any number of things can bombard and eradicate us in an instant.

Many critics have mentioned that the effects of the Color are reminiscent of radiation poisoning. Of course, Lovecraft died a full decade before the atomic bombs were dropped.

The scariest science fiction aliens often have to look scary or do something scary, but the Color Out of Space ranks among the scariest science fiction aliens despite having no tangible form or motivation. It is a presence that spreads death.

The Thing (The Thing)

John Carpenter's remake of The Thing stuck closer to the original novella Who Goes There? by John W. Campbell Jr. than the original film did. In the original movie, the Thing was a giant alien monster who could be lit on fire and still keep fighting.

Carpenter chose to try something different, and, in doing so, created one of the scariest science fiction aliens ever put to screen.

The alien is a colony of microbes. They work together to replicate – and replace – any organic matter they come in contact with. Multiple, fully separate bodies can exist. They all function independently of one another, which means that, in order to kill it, you essentially need to eradicate every single cell remaining.

Flamethrowers are useful, but even they can't completely kill it.

Once the Thing replicates you, it kills you.

The Thing replicates your personality and mannerisms exactly. Even your own mother wouldn't notice the difference. It can walk among a crowd, quietly replacing everyone around it until everyone is part of the hive mind.

But what if you can tell the difference? What if you confront it?

Well, it can transform.

And if you thought it was scary before, get ready for this. Mouths and tentacles all over. It will kill all who witness it, changing its anatomy in an instant in order to maximize its killing efficiency. This is not the sort of thing you can even hope to stop once it's started killing.

It truly is one of the scariest science fiction aliens ever.

Grays (Fire in the Sky)

The aliens from Fire in the Sky are given no particular name. I suppose they're like the gray aliens of pop culture, given that the events of the film are supposedly based on a real event. It hardly matters. Whether fact or fiction, the aliens from this film are scary as hell.

Fire in the Sky tells the story of a Travis Walton, a man who has been abducted by aliens. For the majority of the film, the audience is left wondering what happened to him. We don't even see the aliens at first.

And then Travis pops up again. And, in a flashback, we see what happened. The aliens don't look particularly scary. They look like any other movie alien.

But it's what they do that's so frightening.

The abduction sequence is one of the scariest sequences in sci-fi horror film history. Just the way Travis is bound down in that weird quasi-organic binding, the needles, the screaming – it is positively bone chilling. And you can't look away, either. You just keep staring and staring as it gets worse and worse.

If these aliens are not among the scariest science fiction aliens, then I have no idea what can be.

Tyranids (Warhammer 40,000)

Warhammer 40K is not a nice world - even if it's just a sci-fi game world. It's really quite terrifying.

Fewer sci-fi worlds are as unrelenting or cruel as this one. This world is the definition of grim-dark science fiction. Wars are ended thanks to massive bloodshed, thrones maintaining immortality are fed the blood of thousands every day, and the mere act of space travel is enough to unleash maddening horrors enough to break minds. Only the most hardened bad-asses can thrive in a world as savage as this.

Those hardened bad-asses fear Tyranids.

That makes them among the scariest science fiction aliens ever.

Tyranids are essentially space locusts. They feed on planets, consume biomass, and, after feeding, spawn new Tyranids while developing into far stronger, mightier creatures. It is unknown how many galaxies – yes, you read that right, galaxies – have fallen under the Tyranid hordes.

The more they feed, the stronger they become. So you may think that, by cutting off their food supply, they can be stopped.

Ah, but the Tyranids can release spores that increase life energy in a biosphere, causing all life to grow super fast in order to feed the horde, thus increasing their numbers and power, granting them the ability to overcome any fool who dares halt their progress.

The Imperial Guard and Orks can unleash a hellscape of bullets upon the charging Tyranids, but for every hundred they maw down, millions more are born. And the ones in the rear are the strongest ones yet.

How strong? Well, let me put it to you this way: the Tyranids have caused the numerous factions of the Warhammer 40K universe incredible trouble, coming across as among the most frightening forces the universe has ever seen. The carnage left in their wake is enough to make them the scariest science fiction aliens around.

They've been fighting fringe scouts. Fringe scouts with power enough to depopulate and consume planets. Fringe scouts powerful enough to block out the sun passing through their skies.

...what in God's name is the main horde like?

Weeping Angels (Doctor Who)

Doctor Who has no shortage of scary aliens, but none are more bone chilling than the Weeping Angels. At first glance, they may appear just a little unsettling. They're just angel statues with their eyes covered by their hands. They almost look sweet.

But then you glance away. Or blink.

And then they can move.

Weeping Angels are only frozen in form if someone's looking at them. The moment you stop looking, they are free. And those things are wicked fast. They will chase you down when you aren't looking. In the instant you blink, they can be upon you.

When they touch you, they feed on your potential time energy, sending you back way into the past.

With every successive appearance on Doctor Who, the Weeping Angels became stranger and stranger. Anything that contains the image of an Angel can become a separate Weeping Angel – even the memory of an Angel inside your brain.

Only someone as witty and clever as the Doctor stands a chance against the Angels, and, even then, it takes every ounce of power to endure against the Angels' wrath. But just remember: don't blink. Blink and you're dead.

Good luck.

The Faux Woman (Under the Skin)

No, really. This is one of the scariest science fiction aliens. Yes, I know, Under the Skin is that film where Scarlett Johansson goes completely naked. I know. But look.

Based on the book of the same name by Michel Faber, Under the Skin tells the story of an alien disguised as a woman who lures people to her apartment where she submerges them in a strange black fluid that dissolves people from the inside out. Slowly.

We never get any explanation for this. We never understand why. We don't even really know her character's name. We don't even totally know she's an alien. We just know that she is not human. This is thanks primarily to Scarlett Johansson's perfect performance. She has no understanding of life, reacts to almost nothing, and seems completely driven to accomplish her goals...

For the first half of the movie.

The second half features the alien slowly developing to understand how human people behave and act, making her more sympathetic and intimate with them.

But for the first half?

Early on, we see her undressing a dead woman to put on her clothes. She has no reaction, no empathy, no care.

Shortly after, she leaves a baby crying on a beach, presumably to die. Never once does she even react.

The film is a bone-chilling exercise in apathy. Sometimes, you don't need jump scares or ghouls to be scary. Just sheer disinterest to human suffering.

Xenomorphs (Alien)

No list about the scariest science fiction aliens is complete without xenomorphs. The nightmare fuel brainchild of Dan O'Bannon and H.R. Giger and brought to life by director Ridley Scott, xenomorphs are fear incarnate.

Their life cycle is reminescent to numerous parasitic life forms. They latch onto a body, develop inside a creature's body, before bursting out of their chests in a grotesque, gory fashion. Once out, they shed their skin, growing to a gargantuan size. Phallic-skulled, smooth skinned, and fierce, the xenomorph then has only one purpose: kill.

It's reasons for killing are unknown. They don't eat the bodies of their victims, and they are never seen feeding, so... why kill? For fun? For pleasure?

Xenomorphs combine the hive-mind mentality of parasitic insects and the visceral fear of violation (in particular, rape). H.R. Giger did not accidentally give the xenomorph a phallic head shape, nor is it incidental that their reproductive process involves invading a person's body through a phallic tube that runs down the victim's throat. It is all incredibly sexual and incredibly disturbing.

Due to overexposure, many people have stopped finding the xenomorph too scary. This is an incredible shame, since the creatures remain among the most grotesque and nightmarish creatures ever conceived for the screen. They are the scariest science fiction aliens to ever appear.

Actually, that's a lie. There's one alien race even scarier.

The Outer Gods (The Cthulhu Mythos)

H.P. Lovecraft's Cthulhu Mythos were always a realm of dread and horror, where humanity is a small part of a massive, unfeeling universe. Whereas audiences are familiar with entities like Cthulhu and Dagon, the vast majority of Lovecraft's universe is far, far worse.

Cthulhu can end the world if he wakes up, sure, but Cthulhu – if you can believe it – is merely a high priest to the far, far more malignant entities out there. The scariest science fiction aliens remain too bizarre and insane for Lovecraft to even write about. The vastness of their power is what makes them so damn terrifying, and they are so strong, they're seen as gods.

Lovecraft's Outer Gods rarely appear in his mythos, with the only exceptions really being Nyarlathotep and Yog-Sothoth.

Yog-Sothoth is the source of all knowledge. He thirsts to learn more and be connected with all. He has very little of a presence in Lovecraft's stories, with his only major appearance being "The Dunwich Horror." In the story, he rapes young Lavinia Whateley, forcing her to give birth to two of his monstrous sons. Both are able to lay to waste to an entire English countryside. Neither of them has even a fragment of their father's power.

But Nyarlathotep is far, far worse. Not because he's more powerful, no. He's more dangerous because he notices us. He enjoys to corrupt and play with humanity. For him, it is a game. A delight. He loves to destroy minds and drive man into madness. He has assumed countless forms, functioning as something similar to the Devil.

Though he takes human forms, he is just as powerful as any other Outer God.

And there are countless others. There's Shub-Niggurath, a grotesque cloud lined with cawing mouths and tendrils, the mother of a thousand monsters, each powerful enough to lay a world to waste. There's Ghroth, Olkoth, Ngyr-Korath, and countless others. There are as many entities as they are stars in the sky.

But chief among them – and perhaps worst of all – is the Blind Idiot God Azathoth.

Azathoth exists in the center of the universe. The other Outer Gods spend every moment keeping Azathoth asleep. The universe is his dream. When he wakes up, all will end.

Everything. Gone.


Azathoth may very well be the scariest science fiction creature ever written.

extraterrestriallistscience fiction

About the Creator

Anthony Gramuglia

Obsessive writer fueled by espresso and drive. Into speculative fiction, old books, and long walks. Follow me at twitter.com/AGramuglia

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