Humans love to tell stories, and one of the most fun aspects of coming up with a story is inventing some sinister bad guy to pit your heroes against. As our world has advanced and grown so has our imagination. And that means bigger, more inventive, more horrifying boogeymen lurking in the depths of space.

For this list, we’re looking at fearsome alien races as a whole, not individual alien villains. Some of the entries have been the species of several memorable bad guys. These horrors have inflicted devastation across entire galaxies, their names are always spoken with shudders and their capabilities make the most disturbing nightmares.

These are The 12 Most Terrifying Alien Races From Science Fiction.

12. THE BIORAPTORS (PITCH BLACK)

Nothing quite like imagining the apex predator of an inhospitable alien eco system. When Riddick and the other passengers aboard the Hunter Gratzner crash land on the planet designated M6-117, they are unaware what the planet’s approaching total eclipse will unleash. Approximately every 22 years, the desert planet is thrown into a prolonged total eclipse due to the arrangement of the system’s bodies relative to the three suns.

The eclipse lets the ravenous Bioraptors hatch and scour the planet in search of food. We don’t get a good look at the Bioraptors throughout most of the film, but we see the results of their killing prowess. A cloud of newborn bioraptors, swarming through the air like bats, can carry off and tear a person to pieces. The adults are easily capable of ravaging a human individually.

The eclipse hunting cycles of the Bioraptors have rendered M6-117 nearly uninhabited but for them, so some Bioraptors have been observed cannibalizing their own young to survive. Definitely a reason to be afraid of the dark on this planet.

11. THE ID4 ALIENS (INDEPENDENCE DAY)

Independence Day made the quaint flying saucer aliens scary again. Terror loomed over the world as the aliens’ city-sized ships breached the clouds and slowly drifted overhead, blocking out the sun and disrupting communications worldwide. The anxiety was only worsened when they appeared to stop and do nothing.

The truth was that they were biding their time, strategically positioning themselves for a coordinated, simultaneous attack. When it finally came, the devastation was beyond what anyone expected. Entire cities were annihilated by a single beam of destructive power, millions of lives lost. And their shield technology made them immune to even nuclear weapons.

Then we finally got a look at the uglies. Their biomechanical exoskeletons have broad triangular hoods, skull-like heads and a swarm of lengthy tentacles at their back, each one capable of strangling a human. Part of what made Independence Day such a memorable film was the detail and scope that went into making the aliens terrifying, as a species and individually.

10. THE YUUZHAN VONG (STAR WARS EXPANDED UNIVERSE)

The old Star Wars Expanded Universe may be officially non-canon now, but 40 years’ worth of literature and fan investment isn’t going away any time soon. The Yuuzhan Vong is what happens when the writers throw out their own rules and go on a mad “what if” spree.

The Yuuzhan Vong were an extra-galactic warrior race that first arrived in the galaxy around 4000 BBY and only became known to the wider galaxy in 26 ABY. Fleeing the death of their own galaxy, the Yuuzhan Vong were commanded to conquer the main Star Wars galaxy by their divinely ordained Supreme Overlord. They viewed the hyperspace and technologically driven society of the New Republic as an abomination to their own genetically engineered organic vessels and weapons.

The most unusual thing about the Yuuzhan Vong was that they existed outside the influence of the Force. Jedi could not sense the living Force interacting with them and could not directly affect them with Force attacks. To make them even more fearsome, the Yuuzhan Vong were zealous masochists. Pain and physical torture was Nirvana to them, which meant they were emboldened whenever hurt in battle.

9. THE PREDATORS (PREDATOR) 

When you want to make an action horror flick where you have a team to super soldiers get picked off like teenage slasher victims, you need a serious menace. Enter the Predator. A totally sentient intergalactic hunter that dedicates its life to hunting and killing the most dangerous game it can find. Including humans.

In the first Predator, Arnold Schwarzenegger and his squad are totally unprepared for a technologically advanced alien that’s hunting them. With active camouflage, retractable wrist blades, thermal imaging, and a shoulder mounter plasma canon, it picks off each of his soldier team members without a fight.

Once it sees Arnie get on its level, the Predator seems to toy with him by discarding its weapons and removing its face mask. It makes its evil laugh before death at the end that much scarier. And this isn’t counting the other tactics and technology we see Predators use throughout the other movies.

8. THE ZERG (STARCRAFT)

Bugs are certainly popular inspirations for alien menaces. “The Swarm” of the Starcraft universe, the Zerg hunt and invade the worlds of advanced species, seeking out evolutionary traits to increase their lethality. The Zerg are so menacing that the ancient and advanced Protoss are willing to preemptively exterminate entire Terran colonies to prevent the Zerg from infesting and gaining from them.

What makes them truly terrifying is their cunning application of overwhelming numbers. Many Zerg units can burrow underground, lying in wait for unsuspecting victims. Once they’re in range, all manner of spikes, claws, fangs and pincers can inflict a grisly death. They’re also capable of infesting individual victims like Terrans and deploying them in surprise attacks. Sarah Kerrigan is probably the most famous example, although far from a mindless pawn, she eliminated the existing Zerg command structure and took psychic control of the whole species for herself. The atrocities she commits with the Zerg make them a personally horrifying foe.

7. THE FLOOD (HALO)

The majestic Halo Rings scattered across the galaxy hold a terrible force. In the middle of the Covenant War, the Spartan Master Chief crash lands on the first Halo and encounters gruesome reanimated foes killing and controlling his fellow marines. The so called-Flood are even capable of wielding the weapons and vehicles that their host victims carried.

Over the course of the Halo games we learn that the advanced Forerunners fought a galaxy spanning war against the encroaching Flood. They were so virulent and destructive that no means of conventional warfare would suffice, so the Forerunners built a network of 7 massive installations and fought hard enough to contain the Flood within them. But the Forerunners didn’t stop there. They were so afraid of the Flood that they designed the Halos to emit a pulse that would indiscriminately kill all sentient life in the galaxy. They would rather the galaxy be completely barren of life than risk letting the Flood spread.

Of all the different types of space zombies, the Flood is perhaps the most terrifying in narrative and in gameplay. Not to mention the all-controlling Gravemind, which has one of the creepiest and most ominous voices in gaming.

6. THE ARACHNIDS (STARSHIP TROOPERS)

The influence that Robert Heinlein’s novel Starship Troopers has had on contemporary space sci-fi cannot be overstated. The book codified the space marine and power armor tropes and set the tone and portrayal of interstellar conflict with aliens for a lot of works that followed it. It also happened to introduce a pretty gruesome alien race in the Arachnids.

The “Bugs” took on the true potential of their terrifying power in the 1997 film adaptation of Heinlein’s book. (One of the few aspects the film played up instead of satirized.) Even the common warrior bugs are twisted arrangements of claws and pincers, disemboweling and dismembering the human soldiers by the thousands. Their colony controlling brain bugs are fond of lodging a proboscis in human skulls and sucking out all the brains. Not to mention the tank bugs that can spew jets of supercharged acid and melt you in the blink of an eye. Other media in the franchise went even further with the inventive and gory ways bugs could kill us squishy humans.

5. THE BORG (STAR TREK)

“We are the Borg. You will be assimilated. Resistance is futile.” If you hear those words blaring on the bridge in an episode of Star Trek, you know what’s coming. First introduced in Star Trek: The Next Generation, the Borg are a collective society of cybernetic drones driven to achieve a state of “perfection”. They do this by conquering other worlds and species and expanding their technological and physiological knowledge.

The Borg are terrifyingly efficient. Their ships take on simple geometric shapes that can fire weapons from any surface. Their technology is so comprehensive that they rapidly adapt to and neutralize any conventional weaponry used against them.

One of the unique aspects of the Borg that makes them so terrifying is that throughout the shows and the movies we get a unique perspective into what being a Borg drone is like. Keep in mind, the Borg are not technically a unique species unto themselves. Instead, they assimilate people into their Collective. We get to see plenty of main characters experience assimilation. Their memories and personalities are eroded away as the Borg nanoprobes invade their bodies, installing hive mind receptors and rewriting their DNA to produce the cybernetic augments that make the Borg so recognizable.

4. THE DALEKS (DOCTOR WHO)

"EXTERMINATE!"

The most widely feared species in the whole Whoniverse, which is really saying something. The low budget origin of the Daleks may not have been promising for a terrifying arch-nemesis to the Doctor. But in the 50 plus year history of Doctor Who, they’ve always posed a serious threat to all life in the galaxy.

The Daleks themselves are small, genetically engineered mutants, each of whom inhabit a nigh-invulnerable armored weapon platform that we see most often in the show. The laser canon on their domes is capable of killing anything with one hit. Which comes in handy for them since their only all-consuming desire is to eradicate all non-Dalek life in the Galaxy. Daleks actually enjoy their omnicidal mania. Hatred and malice are things of beauty to them.

It’s a testament to their undying lust for xenocide that they’ve never been beaten once and for all. In a series with Time Lords, who can wield time itself and other supernatural forces against dangerous species, the Daleks have always comeback, even from repeated (supposed) extinction.

3. THE TYRANIDS (WARHAMMER 40K)

There’s no shortage of abject horrors in the grim darkness of the far future. Each major faction from the Imperium of Man, to the Eldar, to the Nekrons, to the Orcs have their own weapons of mass destruction and terrible war machines. But the Tyranids may be the most fearsome at war and conquest of them all. Tyranids are a composite bioform race of many highly specialized evolutions of the same genetic theme. Hideous killing machines, from the size of dogs to the size of Godzillas, all synoptically linked to a Hive Mind that infiltrates, invades and consumes entire planets worth of resources and genetic material.

And they are numerous! A singe hive fleet carries trillions of Tyranid bioforms, all of them controlled by a Nord-Queen that can instantaneously communicate with and direct them. While other species in Warhammer 40K have warred with each other for thousands of years, only 3 Tyranid invasions are detailed in the game lore. Each one of them took just about everything the target faction had just to hold off. It’s also heavily implied that those were just the tips of the galaxy-spanning Tyranid tendrils made up of countless more hive fleets.

2. THE REAPERS (MASS EFFECT)

When the player begins the Mass Effect game series as the up and coming Commander Shepard, it seems as though the rogue Turian Spectre Saren is the most pressing threat in the galaxy. Him along with the tension and hostility between the various space fairing races.

Eventually, Shepard uncovers a horrifying secret with galactic implications. Saren is only the latest indoctrinated herald of the Reapers, a race of colossal eldritch monsters as old as the galaxy itself. They have been cultivating sentient life along an evolutionary and technological path of their own design. And every 50 thousand years, they sweep through the galaxy and harvest every sufficiently evolved species, remaking them into one of their dreadnaught-sized forms.

As if the prospect of being oblivious produce in a galaxy size garden wasn’t enough, the Reapers have developed an insidious and horrifying way of quelling their victims. Reapers exude a subliminal aura that instills an instinctual subservient awe in the mind called indoctrination. It makes any one exposed to them for too long worship the Reapers and rationalize their return. The Reapers are also capable of twisting the bodies of their victims into augmented cybernetic monstrosities when their target species do manage to muster martial resistance. But even then, to the Reapers, we mere humans are just worms carelessly destroyed as they till the galactic soil.

1. THE XENOMORPHS (ALIEN)

They may not be the greatest conquerors or the largest monsters or the most advanced beings (at least in the original movie). But when it comes to terror, Xenomorphs are in a class by themselves. When the crew of the USCSS Nostromo first encountered them, they had already witnessed they destructive parasitic nature of the facehugger and the chestburster.

Everything about the Xenomorph is designed to kill. Their pseudo chitin exoskeleton can stand up to being torched by a flame thrower, and if you do manage to wound it, the acidic secretions it produces can melt starship bulkheads. Its legs and arms let it cover tremendous distances. It has a long muscular tail with a dagger sized barb at the end. And their attack tongue is the stuff of nightmares. Xenomorphs do love impaling their victims, bringing them face to face with their oblong eyeless mouths and biting them with their miniature maw. Their limber, black bodies let them blend into the architecture of the ship, unseen until it’s far too late.

Designed by celebrated surrealist H. R. Giger, and orchestrated in appearance by Ridley Scott for the film, the Xenomorphs were a truly terrifying force of nature. “A perfect organism…unclouded by conscience or remorse or delusions of morality.” 37 years on from the original Alien and no other species in space sic-fi has gotten such a nerve-racking, bone chilling portrayal as the Xenomorph did in that film.

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Are there any sci-fi aliens from space that scare you even more than this lot? Let us know in the comments!