The Top 10 Most Terrifying Alien Invaders in Science Fiction

"They either come here to find some resource they don't have on their own planet, or they want to use us for some unauthorized breeding experiment." —Seth Shostak 

Here, the esteemed astronomer Seth Shostak was speaking about how alien invasions are portrayed in movies (and by extension, in books), and he was quick to suggest that in reality, a scenario where they would come to devastate our planet and kill or enslave us is far less likely. Still, peaceful encounters seldom make for good stories, do they? Give us something to fear, we're hooked. Give us a threat from beyond our solar system (and our wildest imaginations?), even better. Last week we asked you to vote on the top 10 most terrifying alien invaders in science fiction, and the results are in! Read on to find out what species came out on top.

As always, these top ten lists are not meant to be all-inclusive or definitive, but give a finger on the pulse of our communities interests and favorites. Want to see who missed out? Here's the original nomination list from the blog.

Without further ado, based on the combined nominations and votes here on the Discover Sci-Fi blog and the Facebook group, here are your top choices for the most terrifying alien invaders of science fiction.

9. The Fithp from Footfall by Jerry Pournelle and Larry Niven

Yes folks, this week our top ten is beginning with ninth as we have a tie! First up, ninth place, we have the alien Fithp from Footfall by Jerry Pournelle and Larry Niven.

The Fithp resemble baby elephants with multiple prehensile trunks. Sounds kinda cute, right? And as one Discover Sci-Fi Facebook member pointed out, “The Fithp couldn't even take over a single planet while owning the high orbitals. So probably not that worthy of terror.” It might cause one to wonder how they made our list at all. Is it that we are inherently fearful of species with a greater command of technology than we have (ie: anything that could find us before we could find them)? Or, maybe that they rebuked the human’s attempt at peaceful contact, something we mightn’t have expected from a species resembling the peaceful elephant? Perhaps it speaks more to the fact of how deeply the book has worked its way into our hearts than of any legitimate fear the Fithp might stir up. Food for thought!

Regardless of the whether the Fithp are truly terror inducing or not, Footfall, the book in which they appear—and one which is considered by many readers to be the best alien invasion novel to date—is certainly a classic worth reading.

Experience the science fiction classic, Footfall  here on Amazon.

9. The Buggers from Orson Scott Card's Ender's Game

Next, in our tie for ninth place, we have The Formics, commonly known as Buggers. The Buggers are a fictional ant-like alien species from the Ender's Game series by Orson Scott Card. The Formic species consists of hive-minded colonies directed by queens. In Ender's Game, Graff described them as being an insect that "could have evolved on earth, if things had gone a different way a billion years ago," and that their evolutionary ancestors could have looked similar to Earth's ants. 

Anyone who knows anything about ants knows that while they may be essential to our ecosystem, they can do one hell of a lot of damage even in their present day, earthly forms.  Just imagine, for a moment, the kind of damage a much larger, advanced species of them equipped with spaceships and firepower might be able to do! Terrifying, for sure!

The Formics attacked Earth 50 years before the novel begins, attempted to colonise the planet and were barely fought off by a New Zealand soldier known as Mazer Rackham. The first book in the series, Ender's Game, largely stems from the human quest to defend themselves from this species.

Is Ender the general Earth needs? The war with the Buggers has been raging for a hundred years, and the quest for the perfect general has been underway for almost as long. Ender's two older siblings are every bit as unusual as he is, but in very different ways. Between the three of them lie the abilities to remake a world. If the world survives, that is.

Read Ender's Game, the first book in the Ender Quintet here on Amazon.

8. The Scum from Daniel Arenson's Earthrise

In eight place on our list are The Scum, the genuinely terrifying alien antagonists from Daniel Arenson's bestselling Earthrise Series. If you've yet to become acquainted, get ready!  

The giant centipedes came from deep space. They came to destroy us. The scientists call them the Scolopendra Titania. Talk about a mouthful! Everyone else just calls them the scum.

They're nasty bugs. As long as alligators. Lined with claws. Fiercely smart too. And did we mention bloodthirsty?

Thankfully, our boys and girls in the Human Defense Force protect us. The scum thought they could kill us all. We'll give 'em hell!

Fifty years ago, bloodthirsty aliens devastated the Earth. Most of humanity perished. We fell into darkness.

But now we rise from the ashes. Now we fight back.

Marco Emery was born into the war. After his mother is killed, he joins the Human Defense Force, Earth's ragtag army. Emery must survive basic training, become a soldier, and finally face the aliens in battle.

Against the alien onslaught, Earth stands alone. But we will fight. We will rise. We will win.

Join Marco Emery in the battle for earth in Earthrise Book 1, Earth Alone here on Amazon.

7. The Daleks from Doctor Who

"Exterminate! Exterminate!"

In seventh place on our list is The Daleks. The Daleks, are a fictional extraterrestrial race of mutants principally portrayed in the British science fiction television programme Doctor Who, and later immortalized in books.

They don't look nearly as menacing as some of the alien species on our list, but it is hard not to be terrified of something so completely emotionless.  Not to mention, they came around at a time when we, as a society were generally pretty scared of robots, our collective early imaginings of which the Daleks could be said to closely resemble.

If you aren't familiar with the series, or if you are, but haven't read the books, you might not know where to start reading about these heartless and terrible creatures, hellbent on destroying us. We'd suggest Doctor Who: War of the Daleks by John Peel as the place to dive in! 

The Doctor is repairing the TARDIS systems once again when it is swept up by a garbage ship roving through space, the Quetzel.

When another ship approaches and takes the Quetzel by force, the Doctor discovers that he and Sam are not the only unwitting travellers on board - there is a strangely familiar survival pod in the hold. Delani, the captain of the second ship, orders the pod to be opened. The Doctor is powerless to intervene as Davros is awakened once again.

But this is no out-and-out rescue of Davros. Delani and his crew are Thals, the sworn enemies of the Daleks. They intend to use Davros as a means to wipe out the Daleks, finally ridding the universe of the most aggressive, deadly race ever to exist. But the Doctor is still worried. For there is a signal beacon inside the pod, and even now a Dalek ship is closing in...

Start the adventure with Doctor Who: War of the Daleks here on Amazon.

6. The Overlords from Arthur C. Clarke's Childhood's End

They come in peace... don't they?

Childhood's End by Arthur C. Clarke follows the peaceful alien invasion of Earth by the mysterious Overlords, whose arrival begins decades of apparent utopia under indirect alien rule, at the cost of human identity and culture. 

Clarke's idea for the book began with his short story "Guardian Angel" which he expanded into a novel in 1952. Childhood's End sold out its first printing, received good reviews and became Clarke's first successful novel. The book is often regarded by both readers and critics as Clarke's best novel and is described as "a classic of alien literature."

In the near future, enormous silver spaceships appear without warning over mankind’s largest cities. They belong to the Overlords, an alien race far superior to humanity in technological development. Their purpose is to dominate Earth. Their demands, however, are surprisingly benevolent: end war, poverty, and cruelty. Their presence, rather than signalling the end of humanity, ushers in a golden age . . . or so it seems.

Without conflict, human culture and progress stagnate. As the years pass, it becomes clear that the Overlords have a hidden agenda for the evolution of the human race that may not be as benevolent as it seems.

Grab your copy of the classic Childhood's End, here on Amazon.

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5. The Posleen from John Ringo’s The Legacy of the Aldenata

We have reached the top 5!  In fifth place is the Posleen from The Legacy of the Aldenata, also known as the Posleen War Series, the fictional universe of one of John Ringo's military science fiction series.  

The Posleen are a race of genetically-engineered reptilian centaurs with crocodile-like heads. They were supposedly designed by the long lost race—the Aldenata—to be the ultimate warriors. The Posleen invasion is shaped by their (over)engineered physiology - Posleen are omnivores and capable of sustaining themselves by eating a wide variety of organisms (including humans). They must eat almost constantly or starve. Inevitably, they exhaust the resources of every environment they inhabit, resulting in a phenomenon they call orna'adar - planetwide conflicts that always end in nuclear holocaust, with the survivors fleeing in starships to repeat the process on new worlds, leaving lifeless radioactive desert planets in their wake.

The first book in the series is the epic, A Hymn Before Battle. With Earth in the path of the rapacious Posleen, the Galactic Federation offers help to the backward humans -- for a price. You can protect yourself from your enemies, but God save you from your allies!

Find the first book in the series, A Hymn Before Battle here on Amazon.

4. The Thing from Who Goes There? by John W. Campbell Jr.

In a respectable fourth spot on our list of terrifying aliens is The Thing from “Who Goes There?” by John W. Campbell.  “The Thing” from Campbell’s novella made such an impression on filmmakers that it was brought to the screen in the 1951 film “The Thing From Another World” and then again in 1982 with John Carpenter’s cult classic “The Thing”, which is likely where most of us became acquainted with this particular alien.  This year we will be treated to yet another movie remake. Something to look forward to!

"Who Goes There?" is the John W. Campbell classic about an antarctic research camp that discovers and thaws the ancient, frozen body of a crash-landed alien. The creature revives with terrifying results, shape-shifting to assume the exact form of animal and man, alike. Paranoia ensues as a band of frightened men work to discern friend from foe, and destroy the menace before it challenges all of humanity! The story is hailed as "one of the finest science fiction novellas ever written" by the SF Writers of America! 

Revisit the classic, Who Goes There? here on Amazon.

3. The Slugs from Robert A. Heinlein's The Puppet Masters

Want to be completely terrified? Just imagine gigantic slugs that can control your mind. That should do it and that is exactly what science fiction master Robert A. Heinlein imagined with “The Slugs” from his science fiction classic, The Puppet Masters.

First came the news that a flying saucer had landed in Iowa. Then came the announcement that the whole thing was a hoax. End of story. Case closed.

Except that two agents of the most secret intelligence agency in the U.S. government were on the scene and disappeared without reporting in. And four more agents who were sent in also disappeared. So the head of the agency and his two top agents went in and managed to get out with their discovery: an invasion is underway by slug-like aliens who can touch a human and completely control his or her mind. What the humans know, they know. What the slugs want, no matter what, the human will do. And most of Iowa is already under their control.

Pick up your copy of The Puppet Masters  here on Amazon.

2. The Weeping Angels from Doctor Who

How long can YOU go without blinking?

The Weeping Angels are a race of predatory creatures, resembling stone statues. In their usual form, Weeping Angels resemble silent human-sized stone statues in the form of winged angels. Generally, their facial features are bland and serene and their proportions human-normal. However, as they close in on more aware victims they transform to a more horrific, bestial, and demonic aspect with wide-open mouths, vampiric teeth, and clawed hand.

According to the Doctor, the Weeping Angels "are as old as the universe (or very nearly), but no one quite knows where they come from." He also describes them as "the deadliest, most powerful, most malevolent life-form evolution has ever produced." Weeping Angels are unusual as predators in that they neither kill nor directly parasitize their prey. Their usual mode of feeding is to make use of time paradoxes – with a single touch, a Weeping Angel can send a person into the past to a point before his/her own birth, and can then feed off the "potential energy" of the years which that victim would have lived in the present.

Are you a fan of the TV series who isn't sure where to start with the books, or new to the Doctor Who universe all together? If that is you and you'd like to become acquainted with these terrible creatures (from the safety of your favorite reading chair) look no further than Jonathan Morris's Touched by an Angel.

In 2003, Rebecca Whitaker died in a road accident. Her husband Mark is still grieving. He receives a battered envelope, posted eight years ago, containing a set of instructions with a simple message: "You can save her."

As Mark is given the chance to save Rebecca, it’s up to the Doctor, Amy and Rory to save the whole world. Because this time the Weeping Angels are using Mark himself as a weapon to change history. Will the doctor stop Mark or will the angels feast?

Get Doctor Who: Touched by an Angel here on Amazon.

1. The Borg from Star Trek

For the second poll in a row, the Star Trek franchise sweeps the voting to take the top spot! Overwhelmingly, you voted for The Borg as the most terrifying alien invaders.

What does it mean to be human? Is it our relative autonomy? Free will? What would it mean to have that stripped of you, your body co-opted? Does the thought terrify you? It should. But resistance is futile…

The Borg are cybernetic organisms, linked in a hive mind called "the Collective." The Borg co-opt the technology and knowledge of other alien species to the Collective through the process of "assimilation": forcibly transforming individual beings into "drones" by injecting nanoprobes into their bodies and surgically augmenting them with cybernetic components. The Borg's ultimate goal is "achieving perfection.”

As when dealing with any character born of a TV series that was only later made into books, it can be hard for book lovers to know where to start, but we’ve got you! While The Destiny Trilogy by David Mack doesn’t represent the first appearance of the Borg in books, it does feature the Borg heavily and is one you can jump right into without prior experience with the franchise.

Start the Star Trek Destiny Trilogy  here on Amazon.

What nightmares have we yet to encounter?

As another commenter in the DSF Facebook group mentioned, "any alien species that comes to conquer and destroy us may well be beyond our wildest imagination."

Until then we will happily rely on the brilliant creativity of the authors of science fiction who, in the absence of present day alien threat, give us plenty to fear through their books. So what will they dream up next? That remains to be seen, and whatever it is, it may knock one of these invaders right out of our top 10.  As always, these lists are a snapshot of a moment in time in our community and while we are almost certain that some of these favorites will remain, who knows? Maybe the best is yet to come. For now, visit us  here in our Facebook group to chime in on the debate, and then check out our most recent poll while you're there. Don't have Facebook? Feel free to add to the comments below.

*All book-related copy in this post was pulled from Amazon, Goodreads & Wikipedia, unless otherwise credited.