The creatures escaped. We selected them to breed fast. Perhaps too fast. The customers were always hungry for the newest model.

At first, it was just small beasts. Dog-sized. The kind a child could raise instead of a dog or a cat. More intelligent than a dog, and more loyal than a cat.

Then the zoos got in. Suddenly, having natural animals was passe. Visitors wanted to see titans - enormous, scaley creatures with rows of teeth that could crush a car on accident. T-rexes, Triceratops, Stegosaurus...but then we moved on to animals nature had never even seen.

New monsters were being created by the week. Magazines held contests to name entire artificially created species (though that ended rather quickly after a new sea reptile was named Draconia MacDracoFaciem).

But amidst all the excitement and optimism of this new age of genetic recombination, we never considered what would happen if a breeding pair escaped...

I am making a post-apocalyptic world where the cause of the disaster is some sort of genetically created invasive organism. This civilization is so adept at genetic manipulation that, rather than splicing sections of DNA from one organism onto another, they can custom create a new creature from scratch with the same ease as making a 3d model for a video game. At first, the corporations with this technology used it to make real-life Pokemon - cute, fuzzy things ranging in size between a cat and a golden retriever and market-tested to compete against them. The yellow text above goes on to say how zoos realized they could make a real-life Jurrasic Park, and later realized they could make real-life Monster Hunter Park, but I'd like to focus on that last line.

You see, while those T-rexes and wyverns and Gore Magalas survived and thrived after the event, the menageries they were kept in (zoos came to refer to facilities that held naturally-occurring animals) were just too spread out for a single escape to result in the collapse of all civilization. No, the real cause of the end of the world was the little Neo-housepet things. While the genomic technology is versatile to create literally anything that can breathe and grow, it takes a long time to create a single animal. To create enough stock to sell these things like Pokemon cards, the brilliant corporations in charge of this tech engineered their housepets to breed very rapidly. Of course, this meant that they spread like weeds once they got out, especially without any natural predators.

And this is where I get stuck. I'm not sure how to go from this to "civilization is boned." I don't want to make these rats crave the blood of humans because I still want there to be humans after this disaster. But I want the rats - or whatever they unleash - to devastate modern infrastructure with little to no warning. The dinosaurs/dragons can help this disaster along - when the national guard is helping victims of a flood caused by rodents chewing through the wires at a dam, it's hard to get them out and fighting a rampaging T-rex - but the primary cause is the rats. I need help with what these animals do and how they cause the apocalypse.

  • Despite being called "rats" for now, they range in size from about the size of a rat to as large as a dog. Most consumer models have similar features to many quadruped mammals (2 eyes, hair, tail, ect), but any of those features can be played with.
  • This setting plays loose with the boundary between magic and science. For now, let's say that any adaptation that occurs on a real-life animal, such as armored calcite plates, electric-generating organs, or bioluminescence can be put on this rat.
  • As stated, the escaped dinos and dragons can help the collapse of civilization along (most likely by destroying nearby centers of population and the knowledge therein), but the rats have to be the primary culprit in the apocalypse.
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    $\begingroup$ The Trouble with Tribbles... $\endgroup$ Commented Apr 23, 2018 at 18:05
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    $\begingroup$ Normal rats would suffice, if they transmit plague. $\endgroup$ Commented Apr 23, 2018 at 19:15
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    $\begingroup$ You may be able to counter such a threat with "good" mutated rats. Perhaps one that can train other creatures (say, turtles) in martial arts. $\endgroup$
    – bta
    Commented Apr 23, 2018 at 21:06
  • 3
    $\begingroup$ You don't need your creatures to escape. Humans have a long and venerable track record of dumping unwanted pets. I have many friends who have 'rescue dogs' or 'rescue cats' which were abandoned by their first owners. Bits of the UK have terrapins because of the first Teenage Mutant Ninja Turtles craze - the kids eventually got bored of their pets and dumped them in a nearby pond. $\endgroup$
    – DrBob
    Commented Apr 24, 2018 at 15:11
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    $\begingroup$ Maybe they evolve the ability to secrete opiates. They're so adorable that no one shows up for work in the morning. $\endgroup$
    – Beta
    Commented Apr 24, 2018 at 15:13

13 Answers 13


Go full Pik-... electro-mouse on them

These little critters love electicity. It was cute when someone came up with the idea of creating a pet that likes to nibble on your electronic devices. In this day and age everything has some amount of electricity. But then someone wanted a bigger pet that would still be nibbling on electric devices.

And suddenly you had a rat that was attracted to electricity.

After some time they started to slightly shock someone after nibbling on electronics. Still cute, more like being shocked after rubbing a balloon on your hair and then touching a doorhandle. And it was great for keeping all sorts of cats and such off your lawn.

Everything was fine - until some of them escaped and found that there were lots of cables everywhere. It's their favourite snack and every other animal that comes close to them will be shocked as if it just touched a hyper-version of an electric eel. Not something normal rats or cats are used to and so they started to multiply like crazy.

The more electricity, the more of these critters. Defending your precious electricity became the main task of humanity, but they were too fast and they are too small. You can still live somewhat comfortably when not relying on electricity too much, but without any electricity it became hard for humanity to care for themselves and we were pushed to the brink of extinction.

Dragons and all that were a secondary problem. Once we couldn't care for them anymore they escaped and occasionally they eat someone. They are the direct threat that's eating you, but the problem is the secondary threat of these damned rats destroying all your equipment. Once you set up a base and try to provide enough of anything for a couple people they are coming for you. These little critters will destroy your base, leaving you defenseless for the normal wilderness, the new dragons and the problems of too many people in one place without enough food and hygienic facilities for everyone.

They don't kill you directly - but they are the ones that are responsible for the near-extinction of humanity.

  • 2
    $\begingroup$ Mynocks, chewing on the power cables again... $\endgroup$
    – Samuel
    Commented Apr 25, 2018 at 21:08

Breeds fast? Destroys environments? Fuzzy rodent that doesn't crave human blood? Sounds like you made a super coypu that's going to consume the world's plant life.

A Coypu is an annoying, adorable, orange-toothed rodent whose habitat and feeding description begins with:

Besides breeding quickly, each coypu consumes large amounts of vegetation. An individual consumes about 25% of its body weight daily, and feeds year-round.

It seems to fit the bill, and doesn't need any modification besides being bigger and able to breed even quicker.

Real Coypus are a menace: Here is the 2016-2017 report on Louisiana's coypu(also called a nutria) harvest, which is designed to keep their numbers in check. For the 2016-2017 season in just Louisiana, more than 200,000 coypus were culled, a million dollars was allocated to pay the hunters, and it is estimated that nearly 6000 acres of coastline was damaged by the local coypu population. And this is before their genes were messed with.

Your super coypus are worse: Essentially, the super coypus will eat the world into the apocalypse.

Your super coypus just escaped from some rural homes, and reach a nearby river. They start eating, and they start breeding.

A normal coypu weighs about about 6kg. If your coypu monstrosities are dog-sized, let's say they weight about 30kg. If they ate 25% of its body weight daily like a normal coypu, then each one of these things is eating 7.5kg of veggies every day. Presumably, your genetics lab also made nutrient pellets that hid their true hunger from the public. A normal coypu can give birth to 1-13 offspring every 130 days, and you said your rodents were designed to breed faster than normal.

Pretty soon, the super coypu escapee population has outgrown the local wetlands. The plantlife around their rivers is depleted, but luckily for them the rivers they inhabit lead right into nearby crop fields. They begin eating massive amounts of crops and are able to breed and spread faster than ever before. As more super coypus escape around the world and eat their way through farmland, the fear of food shortages grip the world. With governments focused on controlling a panicked populace, attempts to cull their numbers fail.

There's too many to capture individually. Burning and poisoning crop fields to save the food supply is a poor long term strategy.

Eventually, these fuzzy rodent-locusts deplete the environment to the point where their population collapses and they cease to be a major problem. Unfortunately, humanity ran out of food long before the super coypus did.

  • 6
    $\begingroup$ You don't have to wade into science fiction to find plenty of other examples, either. Check out what happened to native animal populations when Europeans first settled New Zealand (and brought along non-native critters) or what's happening right now in the Florida Keys thanks to pet lionfish being released there. Add a dash of genetic engineering as prescribed in the question and it's almost to easy... $\endgroup$
    – dwizum
    Commented Apr 23, 2018 at 19:15
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    $\begingroup$ @dwizum: Yeah, we've been accidentally disrupting ecosystems worldwide for thousands of years. Imagine if we were actually putting some real effort behind it! $\endgroup$
    – Giter
    Commented Apr 23, 2018 at 19:56
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    $\begingroup$ "Your super coypus are worse: Essentially, the super coypus will eat the world into the apocalypse." Nonsense. They'll barely be able to reach equilibrium with their prime competitor, the Kudzu! $\endgroup$ Commented Apr 23, 2018 at 21:49
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    $\begingroup$ @WillHartung: Clearly, we just need to release a bunch of coypus into the areas with kudzu to solve that invasive species problem forever with no side effects. $\endgroup$
    – Giter
    Commented Apr 23, 2018 at 23:11
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    $\begingroup$ Coypu is a good start. Or you could go even bigger with a Capybara. $\endgroup$
    – Simba
    Commented Apr 25, 2018 at 10:35

Initial customer research showed a sizable fraction of household pets died from neglect. This failure mode was then removed from later models. They are now quite tolerant of wide temperature ranges or going long times without food or water.

The next most common problem was poisoning. This too was removed. They can eat anything from asbestos to cornflakes with minimal declines in health.

Getting lost or escaping was the third most noted problem, so they were given a desire to be near people.

Focus groups reported that much of the fun of rodent ownership was in training them to do tricks. Adding a little brain power was seen as a sustainable policy; there was plenty of room before they were intelligent enough for people to feel really bad about accidentally killing them, but a new slightly better version could be regularly released indefinitely.

Oops. They are adept at getting into our living space and nearly impossible to remove. We can't trap them or poison them, their resilience means they don't mind tracking sewer water though our pantries and they inevitably find their way into both. Any counter measures are too extreme to deploy in homes, and even making predators would be risky to humans since the predator would have to be bigger and smarter then the rats.

They breed fast so the response to a known infestation needs to be swift, they are hearty so it needs to be brutal, but every time the clean up crews cordon off a block and burn it down the human refugees smuggle out the pets because they are super-naturally cute and owned by kids.

While officials know that rats are a serious problem (non-super rats' damage is estimated as something like 20% of world wide crops today) they have trouble convincing the general public that they are more of a problem than dinosaur rampages even after being personally effected. "we are only keeping [males/females] so it can't be a problem. Oh drat, the Joneses didn't make the same choice of sex; there goes the neighborhood again. Really Johny next time you ought to take more care of them."

  • 1
    $\begingroup$ "Joneses" is the plural of "Jones". $\endgroup$ Commented Apr 23, 2018 at 21:29

So they were the cutest little critters around, and had already made massive profits for the company - one pet for every home was a target that seemed realistic - the Crispr/Cas-Sets for rapid personalization kits (genetic cures for variations in color, fluffyness and behaviour) were selling like wild, the special foodstuff that contained the precursors for wilder colors and glow-in-the-dark effects (could be done in vivo, but shhhh...) flew off the shelves, and would continue to do so, because the buggers were really tough and durable.

Only problem: about one in a million humans had a harsh allergic reaction to them. So after the first lawsuits, the corporation was ready to pull the plug regardless, when a promising young scientist from the genetics department came up with an idea: While the allergenic factor, and even the brittleness of the older hair (designed and patented dust-away(r) to avoid whole hair uglying up couches) were too deeply ingrained in the genetic makeup to just remove from the DNA, it was a piece of cake to modify some eColi that would live inside its gut and release iRNA to specifically target the offending allergenic factor. The iRANa would bond with the RNA destined to be translated into the allergenic enzyme, no enzyme, no allergy. Profit.

The modified eColi was rolled out as part of a yearly gene-bugfix (complementary). Was it the plan of the geneticist all along (she offed herself shortly after the first reports of malfunction popped up)? Was it a miscommunication with the third party contractor that did the splice on the eColi (what should have been separate for obvious resons was synthesized as one, disabled, sure, but now only one deletion away from becoming active)?

Anyways, the eColi did not push the iRNA of the 1/million-allergen, they pushed the RNA of a 1/1 allergen of epic efficiency. Come into contact once, you'll be itchy and unwell. Come into contact a second time, without immune-dampeners turned to eleven, and you are a swollen, pus-dripping, retching pet owner for as long as it takes for you to succumb to your gut ripping itself apart. And the allergens are everywhere - it's not the hairs - its the broken-down-to-single-molecules hair-dust. Wrap yourself in molecular filters, or you are done. For a brief moment the tide was stemmed by immunosupressants, but as the stockpiles dwindled, normal sickness jumped on the defenseless, and it soon became clear that only [obscure country] that had never imported the pets because of a licensing spat with the corporation, would survive in any shape at all...

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    $\begingroup$ I vote for [obscure country] to be New Zealand. We're fanatical about biosecurity out here these days. We can sit back and watch the rest of the world dying from their Furby allergies... $\endgroup$ Commented Apr 24, 2018 at 0:36

I think you're looking in the wrong direction. I don't think mini-creatures from rat-size to dog-size are going to be a problem. We have them already, in every environment native to humans, and even fairly basic countermeasures will stop them.

Insects, however... Oh boy, are your people in for a surprise there.

For starters, if anyone can do this, then anyone will. Want wasps with box jellyfish poison? No problems. Want to conveniently wipe out the neighbouring church/tribe/country? Air drop a few dozen crates of those bugs, and wait for the screaming to stop. Want to sabotage your competitors? Fill their offices with thunderflies which excrete acid, and watch their computer systems die. Biowar goes consumer-level.

This might not even be the end of it though. After the first few disasters, the companies go antivirus on it, so now everyone pays for their own defense net. Anything comes through the net without authorisation, it gets swarmed by tiny flies to bring it down. Defense in depth means the place is full of anti-intrusion flies. They need to be cheap enough to be disposable, and the only way to do that on a scale of billions is to have them reproduce themselves.

Do the flies go out of control with reproduction? Do they stop people leaving or entering? Do they lose track of their range, so they stop traffic on roads? Do they attack stationary items instead? So many options that your story could use.

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    $\begingroup$ +1 I think this is the direction of wholesale destruction. Contrary to popular opinion, the smaller the animal the harder it is to control it. Consider we haven't been able to eradicate most insects we are dealing with -- roundup is still a growth industry, mosquitos still bite. The only issue with insects is they are usually optimised for warm climes and are dormant in cold weather. Make insects that can breed at - 10C up to +40C, and let's say can eat plastic, and the world is doomed. $\endgroup$
    – Gnudiff
    Commented Apr 24, 2018 at 9:06
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    $\begingroup$ @Gnudiff Humanity's doomed, but plastic pollution's not as much of a problem. $\endgroup$
    – wizzwizz4
    Commented Apr 24, 2018 at 17:40
  • $\begingroup$ Agree, insects are the way to go. Much creepier. An excellent treatment of this scenario appears in Second Genesis by Donald Moffitt. $\endgroup$ Commented Apr 25, 2018 at 16:52
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    $\begingroup$ @AndrewCowenhoven A less creepy but superbly bonkers version of the same idea (in spaaaace...) is The Insect Tapes by Michael Scott Rohan. Well worth tracking down any anthology with that in it. (I've got it in a collection called Space Odyssey, which has nothing to do with Clarke, but also has Harrison Bergeron and The Engine at Heartspring's Centre; it's worth the money just for those three.) $\endgroup$
    – Graham
    Commented Apr 25, 2018 at 17:02

Some genius decided the sensible thing to do was to get them to eat waste. No feeding costs, right? No more having to recycle all that plastic, no more worrying about food waste? Yeah.

Except animals don't behave like that. They soon realised that the wiring in the house was covered in tasty snacks, and that half the plumbing under the sink not only tasted good but would release something to drink at the same time. And all that technology around the home? It might be full of various metals but the little critters would eat the case and then tear the rest apart to get to the tasty circuit boards inside.

The little sods proliferated like mad; eating their way through the infrastructure that we rely upon for food, light, heat, and drink as they went. It wasn't the animals who caused the apocalypse directly, it was the collapse of Just-in-Time supply chains, and creature comforts. Sure, you could replace it all with stuff they wouldn't eat but that takes time, knowledge, skill, and working infrastructure and that - my friend - was disappearing fast.


Simple: they get hungry.

Let's say that this rat-thing is herbivorous, for the moment, because you said you don't want "craving blood" on the reason list. Let's also say that they're basically meaty water balloons with zero natural defenses or fear reaction, because I want to demonstrate how bad this gets. Let's even say that they're extremely short-lived, reaching maturity in a month and dying in under two years. And, for their few advantages, let's say they're extremely quick breeders and live in groups.

What I've made here is basically the crossbreed of a periodical cicada and a locust, except fuzzy. Their rapid breeding and short generational periods means that you'll get thousands of them in under a decade from just one breeding pair. With all those mouths, they'll be eating a lot too. There's too many of them for any predator to eat, and as long as they're still around, they'll be devouring any plant they can get their jaws around. Oh, and they're spreading out as they grow, so even after they eat all the biomass in an area they'll still just keep going outwards. Sure, the ones left behind in the barren wasteland will starve, but they would die soon anyway and the damage is already done - the soil may be fertile from all the dead rats, but there's nothing to grow in it. Humanity could recover from this apocalypse if they adapted to a nomadic style, constantly moving to places the rats just left and replanting in it until the rats come again. However, our current society requires so much food brought in that it couldn't take this strain.

  • $\begingroup$ Thousands? More like millions or billions. $\endgroup$ Commented Apr 23, 2018 at 21:31
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    $\begingroup$ I was going for a conservative estimate. Even if they were slow enough that it was just thousands, it'll STILL be enough to destroy the ecosystem. $\endgroup$
    – Jacob
    Commented Apr 24, 2018 at 15:45

I would assume that one of the things they would build is biological Golems. Creatures of some intelligence build for a specific purpose, like maintaining the sewers, repairing your electrics, farming and transporting your food etc.

You could try an economical approach where humanity collapses as people are losing their jobs to the Golems and only a small portion survives, but it wouldnt be a strong argument as the remainder would just survive with the Golems that sustain them.

You could try this: some rats escape, no biggy. For years they just live in homes and the escaped wherever, growing in number. But they are intelligent and can learn from eachother (so if your neighbour learns a neat trick to his rat your own can quickly learn it too). Some of the rats at some point find out that some of the Golems are tasty. The Golems dont have a survival instinct against predators because they never needed them, and in just a couple of days all the rats learn to eat the Golems as the freshest, easiest food around. Some you can munch without killing them immediately! Wonderful! Since the Golems control tons of important stuff including care for other Golems and humans, the sudden and unprecedented collapse of their work causes a collapse of society and large sections of infrastructure, if only because a ton of the Golems getting munched on were flying planes, driving trucks or controlling the local chemical/nuclear plant during their work.


The rodents multiplied for years, all mostly undetected while doing their favorite past-time - digging tunnels!

By the time the first city started sinking into the ground, there were too many to really stop them; people could only slow the inevitable. Sinkholes were everywhere. Buildings collapsed. Roads all turned impassable. Society slowly and surely regressed as our landmasses collapsed inward and the ocean claimed them.

If you need to explain a little more: Unlike most digging rodents, these actually ingested the soil - all that energy for constant breeding has to come from somewhere. Perhaps their waste was naturally liquid and easily flushed out with any water source; initially to aid in keeping care of them but resulting in exponentially growing amounts of good soil going into the ocean with any rivers or rain as they multiplied.


They were too helpful.

One breed was created to remediate plastic pollution and e-waste. They were supposed to be confined to recycling facilities, but a breeding pair escaped. A population of fast breeders with no natural predators will grow exponentially.

Now, their descendants eat anything with plastics and anything with electronics -- which is to say, all products of modern technological society.


Threadomancy time!

Since you say they were originally intended to be sold as housepets, I'd suggest that the rats emit a pheromone that makes people love and want to buy and keep them. Unfortunately the scientists were so preoccupied with marketability that they didn't consider the effects the pheromone would have in high concentrations.

The presence of this pheromone in a high dosage(indicating a large number of the rodents in the area) causes people to become completely obsessed with them, to the extent that they care only about the rats to the detriment of everything and everyone else. When the effect is further intensified it drives people into a kill-frenzy as they are seized by an irresistible urge to remove any competition to their sole ownership of all the rats, which is every other human on this planet.

This is the start of what one might call a zombie apocalypse. However unlike zombies, the afflicted people retain some of their mental faculties including the ability to use weapons, making them far more dangerous. To make things worse they also don't look like zombies. The authorities would be utterly baffled as madness consumes the populace. By the time they put two and two together, it is two late. The armed forces are not immune either, and society breaks down with crippling damage to large swathes of modern infrastructure in the process. The dawwwww-mination of the rodents is now assured.

  • $\begingroup$ Nice answer! But I am not sure what exactly necromancy has to do with your zombie apocalypse. I always associate necromancy with magic-to-revive-the-dead possibly in a mindless state, but these people are still alive. They are just crazy about the critters, right? $\endgroup$
    – Secespitus
    Commented Jul 5, 2018 at 7:07
  • $\begingroup$ @Secespitus I was actually referring to reviving the question, but your confusion is understandable. Fixed in my edit. $\endgroup$ Commented Jul 5, 2018 at 7:14
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    $\begingroup$ Ah, okay. It's quite normal on StackExchange to "revive" threads. As long as there is no reason to close a question as off-topic someone can come up with a great answer later, which is why there are even badges for going through old questions and "reviving" them. For example Revival and Necromancer (okay, I could have figured out what you were referring to :D) Anyways, nice answer! $\endgroup$
    – Secespitus
    Commented Jul 5, 2018 at 7:19

I would suggest that the apocalypse in your story be caused by the human response to the critters, rather than the critters themselves. Let's say that the escaped "rats" become a nuisance, driving out native species, and governments begin taking steps to eliminate them, such as:

  • introducing newly-designed predators to kill them
  • engineering viruses to infect and wipe them out
  • changing the chemistry of lakes, rivers, etc, wherever the critters "nest"

These in turn would go out of control and bring down human societies.

This is kind of plausible (based on Australia's history trying to wipe out invasive species) and this approach also gives you a way to insert all kinds of weird horrors into your post-apocalyptic world, such as strange plagues and terrifying predators.


I need not write any more than these words

Wild Pigs

"An estimate for the harvest in 2010 was 753,646 or 29% of the estimated feral hog population in Texas. The population model indicated that without harvest the feral hog population was expected to triple within five years (3.33 times initialpopulation), with a 28% annual growthrate."

Just make it so the company tries to hide the animals getting out and by the time the breeding pair have been found there are already millions loose across the world (they snuck onto ships or make them great swimmers).

Then just make it so that they reproduce at a rate that means at 1 million population they cannot be exterminated.

Also model them like pigs, pigs can eat almost anything and in groups of 2 or 3 can kill bears. If you make these things pack animals like wolves then you could have groups of 500-1000 of these things roaming loose across the wilderness.

And as they are from the breeding pair it is unlikely they are fond of humans like the pets.

Then as they are encouraged to be killed you can have millions of pets being killed which will lead to huge increases in scavenger animal populations.

These scavengers will then be forced to eat elsewhere like supermarkets.

The huge packs will then be drawn towards to scavenger animals and led into human settlements, where they will be shot and killed by people then they will turn savage on the humans and kill every last person in entire towns and cities.

I dont know how dark the fiction you write is, even for an apocalypse this imagery might be a bit extreme (mounds of dead pets attracting rats and vultures, then 1000 strong packs of wolf like super animals spreading through towns killing deers, rats, adults and children and anything that's alive)


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