A Death World is a highly dangerous place, where simply going there is considered taking your life into your own hands. It could be from hazardous environmental conditions, such as an acidic swamp or poisonous fog, or from powerful native predators (Here there be Dragons, or worse, something that eats them), dangerous flora, or even all of the above. It's like the entire place is deliberately hostile to human life. (Of course, if it's also a Genius Loci, it just might be!)
Very few people would ever choose to live there, but since anyone who does is almost always a Badass, expect any populated Death World to be a World of Badass by default. Sometimes, The Obi-Wan may hide out here. Alternately, it may beMordor, and/or home for an exceptionally tough and ferocious race. Some actually take advantage of this as a way of training their Super Soldiers on a planetary scale. Sure, half of the population might not survive through adolescence, but those who do should make good soldiers. Sometimes they are genetically engineered. Those who live on such a world may be an example of Had To Be Sharp.
In real life, every planet outside Earth is dangerous, because we have yet to verify that any other planet out there can support human life. The difference is that fictional Deathworlds are more interesting. Generally this means they have a relatively breathable atmosphere, have a compelling reason for characters to get out and walk around, and have a variety of dangerous flora and fauna to menace them. A planet that cannot host human life for any amount of time is just "uninhabitable" and not actually a Deathworld.
For more details, the various Videogame Settings actually do a decent job of describing the various kinds of dangers you might find in different ecosystems, since videogames almost universally have Everything Trying to Kill You. The Dark World is often a magical variant. Don't be too surprised if there are More Predators Than Prey.
There are many place s in the Hunter × Hunter world that are extremely dangerous to humans. Those regions are closed off to everyone except full-fledged Hunters — because Hunters are the only ones who have even a snowball's chance in hell of surviving a visit. The Swindler's Swamp is an exceptionally dangerous area, even to Hunters. The Swamp's entire ecosystem has evolved around deceiving and eating humans, with such friendly wildlife as "man-faced apes" which go out to masquerade as humans and lure them back to the swamp. Swindler's Swamp is used as staging ground of the second phase of the Hunter Exam that Gon and company take. The goal is simply to reach the other side. Everyone who reached this phase is a 1 in 10000 Badass. Out of a group of a few hundred, only 150 make it out alive. The rest became lunch or were killed by Hisoka.
The New World in One Piece could be considered one, as anyone who has been there then on refers to the first half of the Grand Line as "Paradise". Mind you, the first half is crawling with dangerous pirates, many of which have some pretty badass superpowers, seakings, unknown and unpredictable weather phenomena, and of course, islands that are somewhat few and far between, and is thus itself considered a Death World by just about everyone who hasn't been there or the New World. And even by Oda's standards it screws with physics! Islands that are consumed by perpetual fire, or plagued with storms where lightning strikes like a downpour, or a giant, floating one are some of the highlights from what we have seen thus far.
The Megastructure in BLAME consists of thousands upon thousands of post-apocalyptic wastelands stacked on top of one another and compartmentalized.
Apparently the Gourmet World of Toriko, as evidenced in Chapter 112. Seems to be a more hyper exaggerated form of the New World in One Piece, from the little we know about it so far. Rapidly changing climate and weather coupled with ungodly behemoths of destruction? Well, maybe just one night...
Pretty much the entire world of Toriko, as it is filled to the brim with animals that are strong enough to level cities (creatures are given capture levels, and monster with a capture level 5 or higher can topple tanks singlehanded), the worst place being the Gourmet world, a region which basically encompasses 2/3 of the planet, and was originally though to be a paradise since no one who went there ever returned, until someone actually did return, and revealed that it was in reality a nightmarish hell that would kill a normal person almost instantly and even trained professionals who are considered superhuman can't survive without considerable training.
Every Earthlike planet, save one, in 2001 Nights is a Death World that eventually overwhelms the efforts of humans to colonize them: mind-altering spores, periodically being engulfed in firestorms, wasting diseases, and run-of-the-mill hazardous planets and animals. As a few characters occasionally point out, and as humanity learns to great ruin, a few decades is not enough time to fully understand the biosphere of an alien planet. And the one basically Earthlike exception to the mix was actually terraformed at hideous expense, and even then said terraforming will degrade and collapse in a few centuries, rendering the planet uninhabitable. Oh, and even it has a few giant man-killing monsters.
Earth becomes a death world in Blue Gender. The only safety and civilization is in orbiting colonies, and only remains safe for those willing to train to die on the planet.
The titular planet in Hell Star Remina. In addition to being a living planet that consumes other worlds, the surface of the planet is filled with horrible hostile flora, and the atmosphere is not only poisonous, but nightmarishly corrosive as well.
DC: An artificial planet created by Devilance, a New God from Apokolips, is a death world, with automated defenses based upon the strength of the intruders and killer midgets, among various monsters. Seen in 52, the new Blue Beetle, and Salvation Run. Apokolips itself is also something of a deathworld.
Marvel's Ego the Living Planet is a Genius Loci (or Loco) Deathworld. And frequently a mobile Genius Loci Deathworld, meaning it doesn't just wait for you to come to it...
Krypton's Deathworldiness plays a part in the backstory of Superman's deadliest foe, Doomsday; a Mad Scientist dumped a baby onto the surface, where it died instantly. He then cloned the few surviving cells. Repeat ad infinitum until you get a Super Soldier. Comic Book Science at its best, folks.
Aliens Nightmare Asylum takes the characters to the Xenomorphs' homeworld, which is naturally crawling with them and predators nasty enough to keep them in check.
Judge Dredd has the Cursed Earth, the nuke-blasted wastelands outside of the few surviving Mega-Cities, inhabited only by mutants, criminals and exiled lawmen.
Rogue Trooper has Nu Earth. Both of them. Due to chemical warfare, the very air and water are poisonous, and the slightest rip in a soldier's isolation suit guarantees death. Only the Genetic Infantrymen (GIs) can survive unaided.
Nobody Dies: Australia is mentioned to be this post-Second Impact. Nobody Dies Six A Is One Continent takes place almost entirely there, and reveals why: the wildlife has severely mutated, so that even the sheep are enormous, carnivorous monsters (don't even ask about the platypi), the spiders and scorpions have become gigantic and sapient, the few humans left are either freakishly mutated or savages (or both). The sky is permanently covered in dark clouds that never rain, but constantly flash lightning. And there's a dormant Angel underneath the continent, which became the source of all this nastiness after Second Impact spread some of ADAM's body to the area. The Reego (AI spawn of Rei Ayanami with a great love of violence) are sent to make the place safe again... namely, by depopulating it.
The Pokéverse becomes this in Poke Wars after the Pokémon's power dampeners are removed. Forests, bodies of water, caves and even cities become deathtraps for the practically helpless humans that live there.
Mercilessly parodied in XSGCOM. The birthplace of the First Prime of the Tau'ri is a desolate land, where the winds can strip the flesh from a man's bones, where water only falls in the form of snow, and the forests are filled with beasts, consisting of only teeth and claws and anger. This place? Canada.
Knight's and Bishop's quips in KOTOR: The Prodigy of Revan imply that the planet Tharsis is very much like this. And on purpose, this is where the Spartan Union sends their Raider recruits to train. Terrain features include "dense forests, frozen tundras and jagged mountains crawling with beasts out of ancient myth, jungles teaming with ferocious predators and torturous diseases. And then there's the...er...'food.'"
The Angry Red Planet. Space explorers land on Mars but instead of intelligent life, they're constantly attacked by monsters. When the survivors leave, they get a message from actual Martians, telling them never to return (possibly implying that the attacks were fostered on them on purpose).
Nearly every world seen in The Chronicles of Riddick, save Helion Prime, is a planetary-scale deathtrap. Perhaps justified in that most of the planets seen were either uninhabited, or specifically chosen as sites for maximum security prisons.
Westley: It's not that bad. Buttercup gives him a look. Westley(defensively): Well, I'm not saying I'd like to set up a summer home here, but the trees are actually quite lovely. Buttercup's expression makes it clear that in her opinion her true love is stark staring mad.
The jungle inside the board game in Jumanji, down to the plants.
Pandora in Avatar. Except for the resident sentient humanoid species, the rest of the moon is teeming with megafauna. There's at least two shown elephant-sized species and two Giant Flyer species, but you can still survive by avoiding them. But if the planet itself decides that you've gotta go and the local fauna start evicting you en masse, then you're really in trouble. On top everything else, humans can't even breathe the air - it has too much carbon dioxide and hydrogen sulfide.
Soldier is set on a planet which, while almost a vacation spot in comparison to most examples here, has lots of poisonous snakes and insane winds.
Star Wars: Yoda's chosen refuge of Dagobah is nobody's idea of a vacation destination (at least nobody who isn't a Jedi Master). Then there's Tatooine and Hoth, though it's more possible to live on either of those if you're well equipped and prepared. According to several Expanded Universe sources, Felucia is no walk in the park either.
Many hazards of living on Dagobah come up in Galaxy of Fear: The Hunger. A survey team crashed there and couldn't leave, and their malnourished, uneducated descendents, more resistant to disease and well warned about the animals and Man Eating Plants than their parents, have their Apocalyptic Log, which cuts out when their last bit of technology runs out of power.
The asteroid in Armageddon is not only airless, it's covered in big jaggged evil-looking spikes and regularly spews forth masses of gas and rock designed specifically to kill intrepid astronauts.
The film Signs features one of the most dangerous death worlds in existence. 60% of the surface is covered by a fatal, skin-dissolving acidic liquid that also permeates the atmosphere, frequently falling from its skies like rain. All the local flora and fauna are suffused with the acid, with the crowning example being a sentient apex predator that bleeds, spits and excretes the substance through the skin through physical activity. For those of you who haven't seen the film, the substance is water and the planet in question is Earth. It's not a death world to us, obviously, but the alien invaders were another matter.
The dinosaur-filled islands in the Jurassic Park movies (and books) which are even known to Costa Rican locals as "Las Cinco Muertes" (the five deaths). We only get to see Isla Nublar and Isla Sorna though. From Jurassic Park III:
Alan Grant: That's just great. Here we are on the most dangerous island on the planet and we're not even getting paid.
The upcoming film After Earth has Will and Jaden Smith's characters crash-landing on a "class one quarantine planet" where everything has evolved to kill humans. Which turns out to be earth.
The origin of the phrase is probably the science fiction novel (and subsequent trilogy) Deathworld, by Harry Harrison, which predated Dune by more than five years. The planet Pyrrus has very harsh environmental characteristics: twice Earth gravity, very high tectonic activity, a 42° axial tilt, and the occasional 30-meter tides. Life could only survive by cooperating temporarily during crises, so every single living thing (plant, animal, microbe...) is psychic. Not just that, but the high radioactivity causes them to mutate and evolve very rapidly. When humanity settles on the planet, they accidentally piss off the local wildlife during an earthquake, causing every living thing to treat humanity as a continuous "natural disaster," driven by one mutual psychic mandate: "KILL THE ENEMY!". By the start of the story, the escalating war has remade everything into dedicated living war machines (tree roots are now venom fanged Combat Tentacles, etc.).
Tom Godwin loved this trope to bits. His best-known book, The Survivors (aka Space Prison) features a group of humans marooned on a world with an environment the aliens figure will kill them all in short order (high gravity, poisonous flora, rampaging "unicorns" and other beasts). It doesn't quite work out that way.
Another short story has the protagonists land on a paradise world. Unfortunately, shortly after landing their spaceship's engine blows up and other things mysteriously start wearing out very rapidly. It turns out the entire world's geology is based on diamonds, so diamond dust is everywhere.
Simon R. Green:
His Nightside books have the Nightside, which pretty blatantly follows this trope. John Taylor, private detective, even warns against going there an annoying amount of times in the first book, Something From The Nightside. Considering, though, that the girl he was warning, Joanna Barrett, was an illusion to draw him into the Nightside, his warnings didn't do much good but to inform the reader.
In his Deathstalker series the planet Shandrakor fits under this. Everything is trying to eat everything else, even the vegetation. The fact that they're also constantly rutting due to their extremely shortened life expectancies makes it even worse.
In Dan Abnett's Warhammer 40000 novel Horus Rising, Space Marines founder on a planet they name "Murder". Inhabited by ferocious and incredibly fast aliens, and trees that summon storms. If a Marine had not been horrified by the way the aliens threw dead Marines on the trees to eat, and blown up some of them, thus discovering that they caused the storms, they would never have managed to escape. Keep in mind that each and every one of those Space Marines is a genetically engineered Super Soldier trained The Spartan Way and wearing Powered Armor. If they can't get off the planet alive, any normal person would probably be lucky to last five seconds.
Death World is also the name of an Imperial Guard (Catachan) novel by Steve Lyons. It takes place on a death world with a flavor of Genius Loci .
The classic and first WH40K deathworld is Catachan, which is pretty much a copy of Harry Harrison's.
Neal Asher's The Polity novels feature two prominent Deathworlds: Masada, a low-oxygen world where just being outside without the proper gear is lethal enough, but it's inhabited by an ecology of nightmare creatures such as Hooders (giant millipedes armored like tanks, whose mouthparts literally disassemble you in tiny little pieces) ...and the planet Spatterjay, an aquatic Death World where nobody knows how to swim because if you hit the water, chances are you're never coming back. Most creatures and humans on Spatterjay are infected with a symbiotic virus that gives them superhuman strength and regeneration... so that the local wildlife can eat you for longer.
The homeworld of the Idirans is described as one of the nastiest places in the galaxy. The Idirans are naturally incredible badasses and biologically immortal without needing genetic engineering or cybernetics, thanks to hefty pressure from the other monstrous species of their homeworld and its unhealthy background radiation.
Another featured "death world" is quite literally so. The native civilization wiped themselves out long long ago and it is now left as a memorial of sorts, protected by an Energy Being which is dangerously selective about who can visit the surface. Apparently there are many worlds like this, though most people are smart enough to stay away from them and their protectors.
The version of Mars portrayed in the Barsoom books by Edgar Rice Burroughs qualifies. Due to an ecological catastrophe in the distant past, the planet is a near-desert, with an atmosphere that is only breathable because of an eons-old "atmosphere factory" that almost no one knows how to fix if it breaks. Just about every type of fauna is carnivorous, and they're all huge. To make matters worse, in order to keep their populations under control, the various humanoid natives have a culture the causes them to exist in a constant state of perpetual warfare, consider assassination and kidnapping to be respectable and honorable professions, and fight duels at the drop of a hat. And the non-humanoid natives make many Always Chaotic Evil races seem friendly.
Among those humanoid natives—the Green Mennote who aren't particularly man-like, being tusked four-armed big-eyed giants— one individual in a thousand dies a natural death. 98 percent are killed violently, and the remaining two percent voluntarily go on a last pilgrimage down a sacred river where they are eaten, or sometimes enslaved.
Then there's the various hidden enclaves of practically any sort of monster you could imagine. John Carter wanders into one that consists of a sort of intelligent arachnid puppeteer parasite with specially bred near-headless humanoid creatures that they use as bodies. Another time he finds himself in a city populated by people who can make anything they can imagine into a solid illusion. Any old apparently abandoned set of ruins could turn out to be the lair of some bunch you really would have been better off not meeting.
To get across just how tough the Green Men above are...they're nomadic. And they like to camp in any old ruins they happen to find. Those same ruins that might be the lair of some bunch you really don't want to have met.
Most plant life on Cyteen, in C.J. Cherryh's Alliance/Union'verse, is basically a cross between cottonwood and asbestos, and is full of alkaloid poisons and heavy metals to boot. Go outside the precip towers' envelope without protection and you die quick; get a smaller exposure and you die later from lung cancer. The animal life, at least, is slow and stupid. The original colonists started terraforming measures, which they pulled the plug on fast when an anti-aging drug was derived from local biology.
There are the eponomyous Seas of Venus wherein the plants and animals are all varying degrees of dangerous ranging from "inclement" to "you just got killed so thoroughly, your parents are retroactively dead." (This is based on the novella "Clash by Night" by Henry Kuttner writing as Lawrence O'Donnell.)
Redliners. Burned-out, over-wrought veterans with more than a few ill deeds on their consciences are sent along to safeguard a group of purely-civilian colonists on a new world. They were warned that the planet had dangerous wildlife, but it turns out to be an enemy base gone wrong, of sorts — the entire biosphere is a weapons system that evolves itself in response to the defenses (proactive and otherwise) that the protagonists devise. See When Trees Attack for examples.
Drake seems to have a particular fixation with killer plants. Aside from the entries above, there are scenes in The Jungle and Cross the Stars where men die in their sleep because fast-growing plants grew into their bodies. The vampire honeysuckle attack in The Jungle is another prime bit.
Cross the Stars also has the ocean world Tethys, where practically all the sea life large enough to see is carnivorous, and one species can grow to 40 metres long.
Two notables are Prism in Sentenced to Prism, where near everything is silica based (critters with frickin' lazerbeams), and the lush (and hungry) jungle of Midworld from the eponymous book as well as the Pip and Flinx vehicle Mid-Flinx.
Ironically Earth is considered a Death World in his series The Damned, by a coalition of alien races whose worlds all have low gravity, low tectonics, practically no-axial tilt (preventing violent weather) and few true predators. The average unskilled couch-potato human is more than a match for their trained soldiers. Trained Earth military personnel, especially special-operations types, are essentially incarnate demigods of death by alien standards.
C. S. Friedman has used this more than once.
In the In Conquest Born universe, Azea's fresh water is often contaminated by parasites; its animal life is not tameable and very dangerous; its plant life is poisonous to humans if not prepared carefully; and the atmosphere has occasional poisonous deathwinds. The planet was settled by refugees who had nowhere else to go, and they had to use genetic engineering on themselves to survive since they didn't have the resources for terraforming.
The Coldfire Trilogy features Gerald Tarrant spending several human lifetimes to build a Death World ecology in his lands with careful planning and study, as well as at least one example of others trying the same stunt minus the careful planning and study. As the others are mostly adolescents, Hilarity Ensues.
And the planet itself in that trilogy is already a Death World (at least for humans). Tarrant just made his bit of it even more extreme.
And in The Madness Season, the Tyr homeworld is a paradise — two months out of the year. The rest of the year, its extreme ellipsoidal orbit causes the entire planetary surface to either become a hellacious volcano landscape or an icebound crust of death. Any animal that wants to survive is forced underground, where they eat each other for the rest of the year.
Not to mention, also from The Madness Season, the planet Yuang, which is covered with continual toxic clouds and chemical firestorms, and whose atmosphere is laced with poisons so deadly that any contact with it all causes death or severe neurological damage. It's stated that no human could survive there, without help and continuous supplies from other planets.
In David Gerrold's The War Against The Chtorr book series, the Earth itself is turned into a Death World when mankind is forced into a fight to the death with an invading ecosystem brought from another planet. The fact that Chtorran life is naturally more competitive and voracious (coming from such a Death World) doesn't help Earth's chances of successfully resisting the invasion.
Frank Herbert's Dune: Arrakis and Salusa Secundus might be the Trope Maker for many. As of the first novel, only about half of those born on Salusa live past puberty. Salusa Secundus is the home world for the feared Imperial Sardukar. One of the reasons they are so feared and elite is that simply surviving long enough to be recruited makes you a Badass by default.
And of course Arrakis is one massive desert full of Sand Worms that will probably eat you if dehydration or the Fremen (whose women and children are a match for Sardaukar) don't kill you first. At least until Leto II terraforms it, only to change it back 4000 years later because without the worms there is no natural source of Spice
The planet Moros from Douglas Hill's Last Legionary series. The extremely hostile nature of the planet is the reason the Legionaries of Moros are so capable and therefore so in demand as mercenaries.
The eponymous planet in the Stephen King short story Beachworld was covered in a sort of living sand that hypnotized people and worked its way into any machinery.
The planet Kolnar from McCaffrey and S. M. Stirling's The City Who Fought. A volcanic, radioactive, heavy gravity nightmare world, in orbit around a sun with a spectral category of blinding. Colonized by a particularly nasty group of prisoners, they evolved into nigh-unkillable superhumans. It's no help that said natives have a nuclear war once every generation - and they get their weapons-grade nuclear material by hunting a creature best described as a jet-propelled submarine with fangs. And that's one of the nice critters on the planet. The natives' planned response to being infected with a pathogen which causes debilitating, but not lethal effects in many of their number is to deliberately infect the rest of their population, and kill anyone who becomes ill.
In the sequel, they've moderated their practices slightly. They still infect everyone, but they don't kill those who get sick. They just let them live or die on their own without medical help.
McCaffrey's Dinosaur Planet is likewise an extremely active ecology, complete with a mix of toxic alien life and adapted prehistoric Earth life. There are even insect swarms which eat Dinosaurs bones and all.
The Red Star from McCaffrey's Dragonriders of Pern series is an extreme Death World, and Threadfall temporarily converts whole swathes of Pern itself into a deathtrap.
Bas-Lag, the setting used in China Miéville's novels is pretty inhospitable on the whole, but it also contains at least two of its own Death Worlds. The most notable is the Cacotopic Stain where getting eaten by giant caterpillar men is the least of your worries. Death itself probably isn't very high up on the list of bad things that can happen to you. To wit: a large number of people are collectively turned into a giant amoeba, just by coming near to the Stain. This is not the worst place on Bas-Lag. The worst place has giant, nigh invincible, soul sucking moths halfway down the food chain.
The War World series created by Jerry Pournelle is mainly set on Haven, a frigid prison moon with a barely-breatheable atmosphere, 87-hour days, a harsh ecology, and has been a dumping ground for violent criminals for six hundred years. Then a shipfull of refugee supersoldiers move in and nuke the last remnants of civilization, and the neighborhood goes completely to hell. And some of the recent exiles to Haven came from an even harsher planet called Frystaat, which has twice Earth's gravity, blinding ultraviolet sunlight, sandstorms of industrial-grade abrasives half the year, is so hot humans can only live at the poles, and the native life is hunted with anti-tank weapons.
XXXX, or Fourecks, the Discworld equivalent of Australia. When Death asked his library for information about dangerous creatures, he got buried in Dangerous Mammals, Reptiles, Amphibians, Birds, Fish, Jellyfish, Insects, Spiders, Crustaceans, Grasses, Trees, Mosses and Lichens of Terror Incognita that went at least as far as "Volume 29c Part Three." When he asked about creatures that weren't dangerous, he received a simple slip of paper that read "Some of the sheep."
In The Science of Discworld, the UU wizards quickly conclude that Earth is a Death World, as the ridiculously-spherical planet keeps getting hit by rocks, frozen, or otherwise decimated every few million years. One of the wizards proposed something that could survive the various impact-related shenanigans that make planets such a bloody dangerous place to stay: a heavily armoured mile-wide limpet that ate whales.
There's places on the Disc where the magic is so strong and so wild that if you go to sleep you probably won't wake up the same shape. Then there's places like the (long since destroyed) Temple of the Sender of Eight, which was within a few days ride of the most populous region on the whole central continent.
Grayson has so much heavy metals the atmosphere can get lethal at times.
The prison planet nicknamed Hell, which isn't all THAT bad a place, except for the subtly different biochemistry of the local flora and fauna. 'All of it is instantly poisonous for humans to eat—besides one native equivalent of the potato. That tuber merely leaves those who eat it with the (treatable) equivalent of brain damage — and then you'll still die of vitamin deficiencies.
On one world, whick later became the homeworld of the Andermani Empire, native bacteria eat chlorophyll, making colonists starve by destroying all their crops.
Even two of the three habitable planets from the heroine's home system weren't particularly healthy. One (a local equivalent of Scotland) had a really vicious climate and most of its land was mountainous, and their sort-of-Ireland (her birthplace, that is) was a heavyworld (1.6 g) with a year thirty-six months long and lots of pretty nasty wildlife.
In the first section of War Against the Rulls by A. E. van Vogt, the protagonist is stranded on the planet Eristan II with an ezwal (a clawed, fanged, six-limbed, three-eyed, three-ton apex predator with a genius-level intellect and telepathy) after the starship carrying them is shot down. The ezwal sneers at the offer of aid made by the protagonist, who knows something about the planet, and goes off on its own. Less than an hour later it comes running back and practically begs for help.
The homeworld of the Protectors of the Unborn in James White's Sector General qualifies, as the only sentient species there never sleeps and has evolved so that it needs to be continually attacked in order for vital hormones similar to adrenaline to flow through its body, in a similar way as we need to breathe...if it stops being attacked for more than five minutes or so, it will die. The organism is hermaphroditic, and the young are sentient and telepathic from within the womb, as they lose their intelligence when born, and being born sentient would mean instant death. Any world where a species like that evolves qualifies as a Death World.
The Outernet series has the planet Aaaaaaaargh, named after the first and last words said by anyone who visits it.
The Underland jungle. Scratch that, the entire Underland may count. Besides the humans have to deal with intelligent races of Rodents of Unusual Size and Big Creepy Crawlies. This isn't to mention the earthquakes, volcanoes, eyeless plesiosaurs, giant squid and the occasional plague outbreak. Good thing the humans have the bats on their side — otherwise they probably would have been goners long ago.
In Stephen King's novella and movie The Mist, much of New England becomes a Death World of savage alien beasts.
Face of the Waters takes place on an aquatic example. The entire planet is water and a few floating "islands" of coral, inhabited by invincible rammerfish, mouths that can swallow islands whole, orifice-invading eels, and worse. The only actual land is the Face of the Waters, a hunk of bare psychic-radioactive rock that possesses whoever comes near it. The humans face all this with Bronze Age level technology, since there's no metal or trade on the planet.
This trope could have been very easily instead named Planet Of Death, after his 1960 novel. With such wonderful things upon the 'Let me eat you first' carnivorous flora-covered landscape like quicksand-like pits that are actually incredibly intense forms of acid and razor-toothed, flesh-eating birds, this is a place where literally everything that you see has one thought on its mind: it wants to eat you.. After the heavily-armed explorers are wiped out to all but the last two men, they have the following conversation before they get the hell outta there:
Man #1: There's just one more thing. The rules say that we have to give the planet a name before we leave. We haven't done that yet.
While technically not a Death World per se, Henders Island from Fragment fits this trope so beautifully it just has to be included. The entire island's ecology is a vast biological orgy of violence made up of a mix of killer mantis shrimp on steroids and acid excreting Ediacaran fauna. The average survival time for a non-native creature on the island? Two minutes. Everything eats everything. Even tiger-sized creatures are regularly eaten and killed by swarms of badger, rat, and wasp-like creatures. Cannibalism is rampant. Even the "trees", which mostly turn out to be giant killer mantis shrimps as well, want to suck your blood. And they have vertical biting mouths. This fauna is so good at killing that even single celled organisms not native to the island cannot survive here. In fact, there are only two species on the island that won't kill you in horrible, nasty ways the moment they see you. And one of those two can still kill you if you tick them off enough.
Another case of "Biome the rest of the planet avoids" are the Pelagirs from Mercedes Lackey's Valdemar books. Created by the Cataclysm at the end of the Mage Wars, the background mana has been high enough and erratic enough to do what other genres ascribe to radiation for the past two thousand years. It shows, even ignoring the intentionally magebuilt creatures running free from the end of the aformentioned magewars, with some of the most utterly benign areas having plants that try to feel those travelling nearby as if they were blind people or uproot themselves to flee when someone even thinks about setting a campfire. In the places where Red In Tooth And Claw(tm) prevails (the vast majority), it's even worse.
In the Lensman novels by E. E. “Doc” Smith, there are more than a few such worlds. The worst of the lot is Trenco. The entire atmosphere liquifies at night and vaporizes again within a minute of dawn. The calmest winds are only about half the speed of sound; the bad ones are much worse. Sheet lightning is constant. The ultra-powerful magnetic field interacts with the magnetic-field-amplifying substances in the atmosphere and the sheet lightning to generate space warps that prevent light from traveling in a straight line for more than a few yards. Every living thing is mobile and carnivorous (one scene has a plant being eaten, the plant eater being eaten by a carnivore, and the carnivore being eaten by the original plant, all at once!). And this is leaving out the fact that the plants of Trenco naturally produce thionite, a narcotic about a trillion times more powerful than crack cocaine. Lovely world ...
Valeria, homeworld of the Dutch-descended, vaguely Boer-inspired Valerian Marines, probably also qualifies. In the original novels we don't learn much more about it than it being hot, humid and having roughly thrice-Earth-standard gravity. A much later RPG sourcebook elaborates: it's also heavy on volcanic activity, hence full of noxious fumes and harsh weather, as well as singularly hostile wildlife. The Galactic Patrol has a major hostile environments training camp there.
Star Warshas seen just about every variant on the theme in its Expanded Universe.
Haruun Kal may to take the cake. The majority of the planet's "surface" is uninhabitable due to hugely toxic clouds, limiting humans to one giant mesa. This mesa is covered in thick jungle and dotted with dozens or hundreds of active volcanos. Most of the animals, from the big cats and wolves down to the monkeys, are carnivorous and good at it — the only major herbivores are grassers (easily the size of a minivan and named for their habit of eating clearings in the jungle) and ankkox (gigantic tortoises with armored tail-maces). The locals' equivalent of sheepdogs are giant armored predators with hide thick enough to shrug off a lightsaber, which may kill you. There's the usual mix of incredibly deadly and disgusting parasites and fungi, some of which can eat through any metal circuits, even inside a gun or, say, your aircar. Which will—wait for it—kill you. Even the plants are sturdy and tend to be covered in thorns. If you chew Thyssel Bark, you increase your likelihood of contracting fever wasps which will, if not caught, send you into gibbering madness by literally eating your brain before the eggs they've laid in your head hatch. And even if nothing biological kills you, the volcanic gases, lava, and "death hollows" (low points where toxic gases pool) still might. The Korun, humans native to Haruun Kal, are all force-sensitive presumably because anyone not force sensitive died very quickly. The Haruun Kal equivalent of the death penalty is "tan pel'trokal," translating to "jungle justice," where you're left naked and unarmed in the middle of the wild jungle. Of course, because of the nature of the story set there, the humans living there manage to be worse. Haruun Kal's other claim to fame, besides making a good sporting attempt at everyone's life, is that it's Mace Windu's homeworld.
Sullust is another Lethal Lava Land, but one that managed to evolve an ecology and native sapient species. The planet used to be okay, but at one point the Sullustan corporate government decided to abandon all environmental regulations and just transfer the entire population on space stations.
Kashyyyk, the Wookiee homeworld, barely appeared in the movies and long after it had made many EU appearances, is one of these: (Quoted from Wookieepedia, the Other Other Wiki) "The prevalent ecology could be politely described as a "layered deathtrap", as the dangers presented by local wildlife increased as one descended toward the forest floor"
Kessel is actually more of a really big asteroid instead of a real planet. It's a Penal Colony where people sentenced by Imperials go to serve their term, however long that takes. Huge plants (of the factory type, not the living type) constantly refine rock into gas so you don't need a space suit, but the atmosphere is still very thin and unbreathable, meaning you do need a mask. Inside dwellings, Corran mentions that there's enough atmosphere to breathe, but a reek of burned plastic makes him reach for the mask again. Inside the mines there is mostly working air support, but the crystals that are mined there are extremely reactive to any light, so all convicts/slaves have to work in total darkness. And only the guards are given nightvision devices, so it makes guarding easier. And the stuff they're mining? It's produced by gigantic energy-eating spiders.
Korriban, the Sith Homeworld. That alone should be enough to qualify, but then you have to add in the arid landscape, Volcanoes, and Jedi-Eating... things. If that wasn't bad enough, the planet is also basically a necropolis, filled with the tombs of the Dark Lords of the Sith who once ruled the planet. And the spirits of the Dark Lords haven't entirely crossed over...
Despayre, a world featuring in Death Star, has an ecology explicitly like this, with there being approximately no lifeforms which don't have thorns or spikes or poison or something. It's made worse by the fact that it's a Penal Colony full of all the convicts that the Empire thinks are worse and less redeemable than the ones they send to Kessel - Kessel crooks can serve their term and get shipped back out. Sometimes that's murderers and pirates. Sometimes it's political prisoners. Despayre's convicts do have a chance to be shipped up to work on the Death Star, but knowing the Empire they're not going to be freed after. And then it's used to test the Death Star's superlaser. Without evacuating the population.Or the guards.
Perhaps the worst of them all is Malachor V, the planet destroyed by Revan during the Mandalorian Wars. Prior to the Mandalorian Wars it was a lush, agricultural world. After the Mass Shadow Generator devastated the planet, however, it became an inhospitable world covered in jagged mountains and cliffs, with constant seismic activity and extreme lightning storms. Poisonous gas vents became active, and the only living beings on the planet were Storm Beasts—giant lizards that are corrupted by the dark side aura that plagued the planet since its devastation. The planet is also the site of a number of gravitational anomalies, making it suicide for even the most skilled of pilots to try and land there. In addition, the planet's devastation caused a wound in The Force that became the Eldritch Abomination Darth Nihilus.
Said Force wound has the charming side effect of causing great mental anguish to anyone who sets foot on the planet. For non Force-sensitives. Those who are Force-sensitive (and not protected by the negating power of the Exile) are instantly driven into Dark-Side-fueled insanity. It is theorized this is where Darth Revan... 'made' most of his army.
The underground prison world of Piers Anthony's Chthon and its sequel Phthor is a hellish nightmare world. The animals are all deadly and implacable. All the water sources are inhabited by monsters that will either eat you (if you're lucky), or turn you into a distorted zombie component of itself (if you're considerably less so). Native diseases can cause you to suffocate in gallons of your own mucus. The only way out is to either buy your freedom with a gem—only available inside a scalding, unapproachable geothermal vent—or a weeks-long trek through an even worse part of the world.
The Labyrinth originally existed as a prison for an entire race, but over time it acquired malevolent sentience and turned into one of these.
Aberrach also qualifies, as the inside of a volcano with no sunlight to provide energy, combining the worst aspects of sulfuric atmosphere with killing cold and dark. All of the non-magical people died off long ago, and even the demigod Sartan struggle to survive.
Planet Hell in Joe and Jack Haldeman's There Is No Darkness.
Banshee, in John Steakley's Armor. The cold, windy, acidic atmosphere of the planet itself is instant death, even before the Hive Mind alien insects come into play. The main character's survival strategy is to become an utterly nihilistic schizophrenic.
H. Beam Piper's Four Day Planet has Fenris, generally considered the second worst place to live in the Milky Way. It has ludicrous temperature extremes, and a vast array of downright unpleasant wildlife (that is also lethally poisonous to eat, although if you were dumb enough to eat a tread-snail, you had it coming). The economy is based around whaling a gargantuan sea monster that has to be hunted using military-grade ammunition, and while the beastie is being cut up, the people doing the cutting have to have support fire from machine-gunners to make sure everything else in the ocean doesn't get itself a meal. (The worst place to live is Flourine-Tainted Niflheim, The Planetary Hell, which has an atmosphere made of inordinately reactive fluorine; it's not an example, since the only thing actively trying to kill you is the air...okay, that is pretty unpleasant).
Ket in Animorphs: The Ellimist Chronicles. The surface is covered in lava and poisonous gases. The Ketran death penalty is applied by sending someone to the surface. An alien scouting party that lands on Ket wanders around for hours on the surface in environment suits, before one of their scouts accidentally crashes into a Floating Continent miles above the ground.
The Land has the Sarangrave Flat. It is a seemingly typical swamp, perfectly natural and good like all things in the Land. However it also the home of all deadly and poisonous things.
In the Second Chronicles the whole land becomes this under the power of the Sunbane. Every five days randomly the Land gets a years worth of Drought, Rain, Disease, or Fertitily. The people need to use the Sunbane which causes it to survive.
Christopher Anvil wrote a novella titled "The Gentle Earth." The invading aliens came from a very moist world that basically lacked weather or tectonic movement. They thought concepts such as "winter" were human superstitions ... until they experienced blizzards. Before that they learned they'd parked their headquarters in an area nicknamed "Tornado Alley".... note Bonus points: The aliens were amphibious, and they had no defense against Terran diseases like the flu.
Deathship Earth, the bad future in Norman Spinrad's Anvilicious He Walked Among Us, where global warming has forced the remnants of the human race into domes improvised from shopping malls, recycling their wastes. The rest of the planet is a scorched wilderness, apparently inhabited only by a half-rat, half-cockroach scavenger species.
Literal deathworlds exist in the world of the Myst franchise, and play a role in the novels. These are linking books that teleport the user to places utterly inimical to life, such as a planet with a molten crust or the heart of a sun. There is a reason the D'ni make their initial assessment unknown/potentially deteriorated ages in a heat-resistant, airtight, radiation-proof spacesuit with a light-blocking faceplate that automatically pulls the user back after two seconds in the age, returning to a fireproof sealed decontamination cell. All of these safety precautions turn out to be necessary (and effective) the very first time such an assessment is made in The Book of Terahnee.
In Sergey Sukhinov's Chronicles of the 21st Century, Venus is described this way. Besides the Real Life reasons of scorching heat, poisonous gases, acidic rains, and low visibility, there are also strange non-carbon-based plants that form a lush forest on a certain plateau. Some of these plants behave in a very plant-like manner, able to uproot and move on their own. They can also defend themselves if necessary and even hunt for food. Even though humans are inedible to the plants, it's usually too late for the poor saps (no pun intended) who end up a tree's lunch before being spat out. Additionally, due to many atmospheric factors, it's almost impossible to solve murders outside the domed city.
The planet in Robert A. Heinlein's Tunnel in the Sky. It doesn't look too bad, at first. Swampy-jungly-foresty place, seems to have largish predators, but nothing TOO obnoxious for a high-school student. Didn't I mention that? This is your pass-fail graded final exam in PLANETARY SURVIVAL. Live to reach the pickup point, and you get a PASS. Oh, and to make SURE you can't cheat and read up on specifics of the place, this planet's just been discovered recently and all we actually know about it is that the environment won't AUTOMATICALLY kill you for eating, drinking, or breathing. Good luck! See you in a week!
Oops, sorry we ended up leaving you there for two years, there was a supernova. So, how many of you are still alive?
Lusitania in the Ender's Game series has exactly six native species thanks to a genetically engineered disease called the descolada by the human settlers ("ungluing" in Portuguese). Humans are not part of the descolada's artificial ecology, so it kills them.
A number of planets in Jerry Pournelle's CoDominium series, mostly used as dumping grounds for "undesirables" during the CoDominium's reign. During the Empire some of those planets, such as high-gravity Frystaat become known for their mercenaries.
The best way for the surviving inhabitants to improve their health? Eat the feces of the small number of people from the Moon sentenced to work on Earth in various reclamation projects, since they shed a certain number of their medical nanites (which remain viable for quite some time) in their feces.
The alternate Earth of the Destroyermen series. The series takes place mainly in the islands of southeast Asia (the Phillipines, Borneo, Malaysia, etc.), so you're in the Ring of Fire, meaning there's occasional earthquakes and volcanic eruptions. The dinosaurs never went extinct on this Earth, so on land, you've got carnivorous dinosaurs and other reptiles with too many teeth, including an intelligent human-sized lizard species called the Grik that serves as the series' Big Bad. One island has a sapient amphibian race that doesn't take kindly to intruders. Another has a kudzu-like plant that reproduces by sprouting roots inside critters that get scratched by it. At sea, there are any number of voracious predatory fish species (the most prevalent being basically piranhas IN SALTWATER!), "mountain fish" that can eat ships, and hurricanes that can be worse than those on Earth. The alternate Earth isn't so horrible as to prevent organized societies, however.
The Russian Shared UniverseDeath Zone has localized variant of this in the form of the Five Zones, which formed at the sites of cataclysmic explosions (the result of a failed wormhole experiment) that wipe out several major cities, including Moscow and St. Petersburg. The Zones are surrounded by bubble-like gravity barriers. At the center of each Zone is a perpetual vortex that links each Zone with the mysterious extradimensional Node. Rampant nanotechnology (originally designed to terraform Mars) is ubiquitous in the Zones, and anything infected by it turns into a mechanical zombie of different kinds. Any vehicle turns into a dangerous version of itself armed to the teeth (e.g. tractors with plasma guns) and behave largely like animals. Any human that gets infected and doesn't receive treatment soon is turned into a "staltech", a mechanical zombie that lumbers through the Zone with an unknown goal and attacks any human (or sometimes another zombie) it sees. Despite this, a good number of people still come to the Zones in search of fortune and adventure, as finding and selling Artifacts is a lucrative business, even though these artifacts refuse to work outside the Zones' anomalous field. Most do not survive. Those that do are called stalkers. Making it a year in a Zone automatically makes you elite (the Zones have been around for only a few years, but many characters treat it as if they have been there for decades if not centuries). Add to those difficulties various anomalies, such as an anti-gravity field that lifts you up and, after you glide out of it, normal gravity takes over, and you plummet to your death. The world outside the Zone is pretty much the same, but inside definitely fits the trope.
Also anyone infected with the "scorgs" (rogue nanotech) can be saved, but only by a trained specialist who converts infected areas into usable implants. As with all Zone tech, it stops working a short distance from the Zone, and many of these implants replace vital bodily functions. This means that, for most, leaving the Zone is a death sentence, but then most stalkers can't imagine living in the Big World anymore.
Brian Aldiss's novel Hothouse (AKA The Lord Afternoon of Earth) involves a distant future, where Earth has become tidally locked with the Sun (which has also expanded), so that one side constantly faces the scorching heat, while the other remains in perpetual darkness. The sun-facing side has become the titular hothouse, with giant plants constantly vying for supremacy and most of the animal kingdom dying off. Plants are now extremely dangerous to each other and the remaining animals (humans included). Humanity is facing extinction. Humans are now a fifth of normal size and live on the giant trees. They constantly have to be wary of the Man Eating Plants, and the four remaining species of insects, which have become Big Creepy Craawlies. There are also Flymen, who periodically come and try to take human babies. It's revealed that they are humans mutated by cosmic radiation and rendered sterile; that's why they capture babies. Not much is known about the Nightside, except that it is very cold and that there is a race of baboon-descended people called Sharp-furs living there. Oh, and Earth is destroyed by giant solar flares at the end with life beaming itself to faraway stars.
The world created by the release of ice-nine in Kurt Vonnegut's Cat's Cradle certainly qualifies.
The Death Zone on Gallifrey, a site where the most dangerous monsters in the universe (the Daleks and Cybermen are banned, but that doesn't stop them from appearing anyway) pit battle with one another in the Game of Rassilon.
The planet of Androzani Minor from The Caves of Androzani features regular semi-volcanic mud bursts, is inhabited by a (admittedly rather unconvincing) carnivorous creature and is the native environment of a mineral which, in its raw state, will kill you within a few days if you so much as touch it. Not to mention you can get shot for being in the wrong place at the wrong time, as there's a rather brutal war going on.
The planet Spiridon in Planet of the Daleks is a good example. Plants that spurt quick-hardening glue that can trap you or close off your airways. Plants that shoot spores that, if they touch you, starts growing in your skin and spreads fast. Tons and tons of carnivorous beasts. Hostile, invisible natives. Honestly, when the army of insane alien killing machines is the least of your worries, things are bad.
The planet Skaro—a delightful wasteland which experienced a nice long NBC campaign by two opposing sides, leaving it essentially a polluted, radioactive stone quarry. Also, there are the surviving inhabitants...
The eponymous planet from "Midnight" is seemingly made entirely of precious gems, and as such has a stake as a high-class vacation planet... as long as you stay inside, as the reason the planet's soil has turned to gems is because it's constantly exposed to a form of radiation that would incinerate anything living in two seconds flat. Except for a nasty little body surfer...
The planet Marinus from The Keys of Marinus. Glass beaches lapped by acid seas. Jungles full of hostile plants and deadly mechanical traps. Frozen wastelands patrolled by packs of man-eating wolves. Bodiless, telepathic slavers. Then there's the WAR...
The planet Eden in the episode "The Way To Eden". Looks beautiful, but beware of differing chemistry; the fruit is poisonous and the grass has acid for blood.
The planet Gamma Trianguli VI in "The Apple", including plants that throw poisonous thorns, rocks that act like anti-personnel mines and directed lightning strikes.
Vulcan itself is pretty harsh by human standards, being extremely hot, dry and rugged, subject to intense electrically-charged sandstorms, and home to man-eating plants and giant, venomous cat-like carnivores (which are freaking adorable and the vulcans keep them as pets!).
Star Trek: Voyager's "Demon" (Y-class) of planet probably qualifies, although the Federation has armored space suits sufficient to let humanoids brave the crushing gravity, poisonous atmosphere, and intense heat. The shapeshifting "silver blood" native to it was a bit more problematic.
Several worlds in Firefly are Death Worlds, due to toxic interaction between Terraforming and the local environment to try to make them Earth-like. These worlds are generally referred to as "black rocks."
The monster-infested main setting of Mortasheenis this, with the creator even mentioning that "[the setting] has enough deadly exponentially replicating organisms that they just cancel each other out. "
This is the official term used by the Imperium of Man in Warhammer 40000 to designate Single Biome Planets of this description. They're depressingly common, but any native populations are automatically prime recruiting stock for the Imperial Guard or Space Marines - indeed, several such planets were colonized specifically to provide badass soldiers for the Imperium's armies. Rogue Trader characters who hail from a Death World get some serious stat bonuses, because even the biggest wimp from that planet still survived to adulthood on a world seemingly crafted to kill them. Some examples are:
Catachan, a jungle world where nearly every animal there is said to be a carnivore, and so are the plants, the majority of the microbes, fungi, and viruses. Wildlife includes the Catachan Barking Toad, a "jumpy" critter that detonates into a cloud of toxins that kills everything within a kilometer radius if you startle it, and the Catachan Devil, a cross between a scorpion and centipede the size of a train, and is thought to be related to the Tyranids. Every settlement fights a daily battle to keep its structures from being reclaimed by the vegetation, feral orks breed in the deepest parts of the jungle, and on top of everything else the planet's gravity is slightly higher than normal. Living past the age of ten on such a planet is considered an achievement akin to graduating from boot camp, making the Catachan Jungle Fighters legendary among the regiments of the Imperial Guard.
Fenris, a world that is exclusively Grim Up North. Its elliptical orbit takes twice as long as Terran standard and means that its long winters freeze almost the entire planet, while its summers bring lava flows and tidal waves as the world passes close to its sun. The land is constantly changing, making permanent settlement impossible, and its resources are so meager that its population must war amongst itself to survive. Other claims to fame include kraken, dragons, and wolves the size of tanks. The Space Wolves wouldn't have their homeworld any other way.
The Blood Angels hail from Baal, an irradiated, mutant-infested, post-apocalyptic hellhole. They seek out similar worlds for training and recruitment purposes, such as an asteroid field orbiting a black hole where quakes can send mountains falling into the void, all sorts of evil nightmares lurk about, and it's a thousand miles to the nearest neighboring asteroid. This make the recruits' transformations into the most angelic of Space Marines all the more miraculous, and may help explain the chapter's preference for shock assaults.
The Salamanders' homeworld is the binary planet of Nocturne, a rugged place of volcanoes, ash deserts and earthquakes, as well as fire-breathing reptiles the Space Marines take their name from. Every fifteen years the Time of Trials begins as Nocturne's moon Prometheus swings close, putting the already high seismic activity on overdrive, threatening every settlement save for the seven Sanctuary Cities. Afterward the planet is gripped by a long and bitter winter that covers the world in a frozen tundra, the only solace being the fresh veins of mineral wealth exposed by the cataclysmic upheaval. There is a reason the Salamanders fight more to preserve life than kill enemies: they know how precious it is.
The world of Urisarach was a storm-wracked planet covered in dense, hair-like forests, home to a nigh-extinct race of huge, armored arachnids dumped there because the monsters were just that unpleasant. It earned its nickname after a failed incursion that nearly wiped out an entire expeditionary fleet of Space Marines: "This. World. Is. Murder."
Yet these are relatively mundane locales compared to Daemon Worlds, planets utterly corrupted by the warping influence of Chaos, where reality is reforged on the whims of daemons and the laws of physics are guidelines at best, the results looking something like a collaboration between H.R. Giger, Heironymous Bosch, and M.C. Escher. Despite being the home turf of the Legions of Hell and the fact that some planets may be literally trying to kill you, a few foolhardy explorers brave the Eye of Terror and search these worlds for ancient relics, for many are former Eldar homeworlds lost in the warpstorms of the race's calamitous Fall. The ones that survive probably wish they hadn't.
The jungles of Lustria in Warhammer are everything nasty about the Amazon with the added benefit of Lizardmen whose Mayincatec culture is fine with human sacrifice. The Dark Elves' homeland of Naggaroth is a shadowy, bleak continent whose native wildlife includes hydras and cold ones (flesh eating dinosaur-like creatures), and with sparse resources that force its cruel inhabitants to turn to piracy to survive. And worst of all, of course, are the Chaos Wastes, the polar regions around a gaping hole in reality that leads straight to hell.
As of the Storm of Magic, the entire Warhammer has become this due to the huge infusion of raw arcane energy. Now it's anyone's guess whether that forest consists of normal trees or EVIL DEATH-TENTACLE TREES OF HORRIBLE TOXIC DOOM. You don't want to know what some of the other terrain pieces are like.
The Forgotten Realms has one of these in the form of the Underdark, a massive underground realm full of all sorts of things that want to kill you. If it's nasty and it's murderous, it probably lives here—indeed, half the reason Drow are so tough is because they spend half their time fighting some of the nastiest things D&D has to offer, and the other half fighting the other inhabitants of the Underdark.
Eberron has a lot. First there's Khyber, its underdark stand-in. Then there are certain planes of existence (Xoriat, the plane of madness, Shavarrath the Battlefield, Mabar, the plane of death, etc...) and some evocatively named regions of the mortal world: the Shadow Marshes, the Mournland, Frostfell, the jungle continent of Xen'drik & the Demon Wastes.
Dark Sun's Athas, a world rendered barren by overuse of magic, which in D&D 2nd Ed. had you starting at level 3 so you weren't killed the first time you stepped outside. As Yamaraput it—
Our scans show that Hard Fun has only about five weeks left.
The Lower Planes. Besides the infestation of devils, demons, and other nasty things, 3.5 makes them quite literal death worlds. In several senses. The Abyss' colloquial description is "Too horrible for conventional wisdom to comprehend" (one of the random things you can encounter on its infinite layers is an ocean of insects, for example), and the Nine Hells of Baator are all actively trying to kill you in some way shape or form:
Avernus: Giant fireballs from the sky. Dodge them and you just have to avoid the endless Blood War campaigns that'd love to have some cannon fodder. Dis: Superheated environment meets government that makes 1984 look like happy flower hippies. Minauros: Acid swamp perpetually absorbing the structures built on it, largely a wilderness in which giant things lurk which the devils are afraid of. Phlegethos: Fire-dominant environment. The landscape is made of volcanoes and magma. The entire landscape. Stygia: Cold-dominant environment. The entire landscape is glaciers and stop-your-heart-in-seconds water. That also rips out your memories. Malbolge: Before Glasya, a land made entirely of hills suffering perpetual landslides from mountain-sized boulders. Now, the entire landscape is alive, and guess what it wants to do to you? Maladomini: A morass of sludge and filth that makes anyone who visits lose all motivation. And the air is acidic. Cania: Major cold-dominant. Breathing kills you, or you freeze to death first. Nessus: One big flat plane, with some canyons. You have nowhere to hide from all the forces of the heart of Hell. No, the canyons are worse.
As of fourth edition, Baator is now a planet◊. The one thing that won't kill you? Falling from the upper atmosphere, which is where most people who come here arrive. Why? Because the place isn't merciful enough to kill you that quickly.
In Planescape, no layer of the Abyss was considered "safe". However, the Fraternity of Order tried to catalogue the layers, and if they labeled one of them "interdicted", it meant "avoid at all costs if you value your life". Layers that got this label tended to have environmental hazards that were lethal to humans, and the descriptions of each such layer often came from the sole survivor of the expedition team that discovered it.
Of the domains of Ravenloft, Necropolis is the most extreme Death World, draining the lifeforce from any living creature. Bluetspur, Saragoss, Timor, the Wildlands and Keening are likewise hostile to human life, and the Shadow Rift can make you vanish from existence if you enter it the wrong way. The Mists themselves can be a Death World too, depending on what you encounter there.
Limbo, the dimension of utter chaos. While most of it is just boiling 'nothing specific' that only takes form when subjected to conscious will, there is a large island of stable land floating there too. It is a jungle and an extremely deadly one - since chaos-infused creatures acquire Healing Factor by default, any predator living there has to be all the more deadly. And the constant mutation gives evolution more chances to get the 'ultimate predator' right than seems believable. Not that the local plants are any better...
And, putting all the rest of the examples to pitiful shame, you have the Far Realm. Try to imagine a place where Lovecraft's monsters would not only originate from, but would be the most basic form of life. Now remove everything even remotely resembling the laws of physics, in any possible way. Now make it a billion times worse than that. You're not there yet, but you're starting to get the basic concept.
Phyrexia is pretty much a techno-organic hell, complete with nine spheres, each with its own charmingly bloodthirsty hazards. The Other Wiki has a pretty detailed description.
New Phyrexia may not be mono-black like old Phyrexia, but that just means it now has five different flavors of horrible death.
Grixis and Jund, from Shards of Alara are death worlds. Grixis is similar to Phyrexia: cut off from green and white mana, the sources of life, it's a dying world infested with armies of the living dead, which fight furiously over the limited (and dwindling) supplies of life force, and even that apparently tastes like stale water or air. Jund is a world cut off from blue and white mana, the sources of order, and is a wild, volcanically active jungle filled with canyons, dragons and similar beasties on the top, and everything trying to kill you on the way up or down. On the bright side, the life magic is strong enough and the food chain is so horrifyingly efficient that there are no undead.
Naya, the green-centred shard, also qualifies. At first glance it may seem less threatening than Grixis or Jund, assuming your first glance happened to miss the 50 foot tall monsters walking around the place. Fortunately, they're prone to missing you too—just don't get stepped on. And don't offend the natives, who worship them. And also watch out for the plants, who have to fend off the herbivorous behemoths. And...
The recent plane Zendikar is shaping up, too. Zendikar is a world where D&D-style adventuring isn't the path to wealth and glory, but survival. Full of ancient ruins filled with booby traps, with variable gravity, the land itself alive and cranky, and a chaotic force called the Roil ripping through and randomizing the landscape...well, let's put it this way: the largest center of civilization on the whole plane is a city of vampires.
"Granted, the world of Zendikar itself has done its best to kill you. A geopede bit clean through your leather climbing harness two miles up a sheer face of Mount Valakut, plunging you into a ravine—which fortunately bore water, but unfortunately also bore some rapids-loving breed of piranha. The same second you managed to get your hands on one of those strange stone hedrons in Turntimber, you crashed headlong into a crude earthen pit, facing a baloth who looked like it had just heard the dinner bell. You had almost arrived at the misty Jwar Isle, with your maps and guides intact, when the sea decided to take your journey personally, coalescing into an enormous, briny maw and swallowing your galleon whole, washing away all of your cargo and most of your resolve...you've seen more than your fair share of trail guides perish under rolling balls of lava, snatched up by hungry-tentacled gomazoa, or shriveled up skin-to-bone by a fierce case of mire blight, but that's the open trail for you."
Zendikar is even a Death World for the Eldrazi. The entire plane is actively fighting against the Eldrazi. It's losing, but still.
The plane of Rath, an artificial plane created by Yawgmoth (yes, that's the same guy who runs Phyrexia) as a forward base for attacking the plane of Dominaria. The entire plane is made of "flowstone", a semi-intelligent rocklike material that can be commanded to take any shape or form. It contains such lovely locations as the Death Pits of Rath, the Furnace of Rath, and the City of Traitors. It is also (probably) the original home of the slivers, a species of vicious, predatory, vaguely insectoid creatures with a hive mind that not only allows them to share thoughts, but also physical traits. Any sliver born with a new mutation quickly passes that trait onto the rest of the hive, and this rapid adaptability makes them a deadly menace to most other forms of life. When the invasion came, the plane of Rath "overlaid" itself on the central plane of Dominaria, ceasing to be a distinct plane and unleashing its myriad horrors on Dominaria. (The stronghold, however, overlaid on a volacno; the slivers, in the bowels of the fortress, were cooked alive. As it turned out, though, extinction only delayed their threat.)
Dominaria itself spent some time as a Death World during the Time Spiral block. The multiple disasters and near-apocalypses the plane had experienced (including, among other things, the above-mentioned Rathi overlay) had destabilized the fabric of reality itself in this plane. Numerous "rifts" appeared, creating highly unpredictable magical phenomena, bringing in strange creatures from other times (and even other timelines), and draining mana from the plane, ultimately threatening to destroy it—and, since Dominaria is the central plane of the Multiverse, all other planes as well.
Things really went to pot for humanity in Innistrad — a plane that embodies Hammer Horror — when their guardian angel Avacyn went missing. The werewolves, vampires, demons, zombies, and other supernatural nasties pushed humans to the brink of extinction. Things got better once Avacyn returned. As in humans actually have a fighting chance of not going extinct in a generation or two.
Sarpadia from the Fallen Empires set became a Death Continent for anything that wasn't a Thrull or a Thallid after those two races turned against their masters and conquered the whole damn continent. Even the Phyrexians couldn't handle the place. They fled the continent after the Thrulls curbstomped them and dreaded the possibility of Thrulls somehow invading the greater Multiverse.
Banshee, the planet where most of the action is in Deadlands: Lost Colony, is a place where evolution got dialed to 11 a long time ago; even the tamest places on Banshee occasionally have to deal with a humongous lizard-like creature called a "Rex" by the locals. There are worse places. Banshee doesn't like it that way, either.
Legend of the Five Rings gives us the Shadowlands, which are a bit of Hell on Earth... literally. Not only is it home to such jovial creatures as tribes of murderous goblins, gigantic man-eating Oni (i.e. demons), and not only is the landscape full of every devious trap regular Nature can devise (tar pits, deserts, poisoned rivers...), but the geography itself changes dynamically so that the traveller will get hopelessly lost. Oh, and of course, who could forget that the longer you stay there, the more you'll catch the Taint, an uncurable and disfiguring disease that eventually turns you into a zombie or Oni. All in all, not a very tourist-friendly place.
This trope is partially averted in the Star Drive campaign setting. Though there are a number of death worlds throughout known space, human technology is generally capable of overcoming the worst effects. For instance, one former death world is now the capital planet of a major stellar nation.
Niflheim, the moon of the planet Mjolnir in Traveller. It is covered by a vast slimy blanket of creatures that are either microbes or nanobots left by Precursors. No one is sure as no probe has even lasted long enough to say; every one gets devoured in a few hours. Not only that, observers aren't even sure the whatevers will be polite enough not to leave the world.
Even the Yu Gi Oh card game has this, in the form of the Field Spell card, "Venom Swamp," which slowly kills everything except the native Venom monsters. There's also "Zombie World," (a world where everything is a zombie!)
The tabletop miniature game War Zone has a supplement describing the flora and fauna of the colonized Venus as basically consisting of giant carnivorous plants, dinosaur-like lizards, deadly bacteria infesting the waterways and quicksand pits every inch you dare to tread. And that doesn't even include the Dark Legion's nightmarish troops lurking in the jungles.
Earth itself in Eclipse Phase, which could be loosely described as a burned-out, ecologically wasted hell zone occupied almost exclusively by carnivorous nanobots, death traps, Exsurgent strains, and killing machines that exist solely to rip off heads and upload the ego contained therein for unknown reasons. A few others have been found through the Pandora gates, not counting the many with unbreatheable atmospheres they include:
Droplet: Has enough six-meter alien crabs that the colonists carry weapons at all times.
Echo IV: Known for its aggressive megafauna.
Nott: Frozen ice ball, in addition there is something out there killing people, possibly living possibly not.
Solemn: has a bacteria that eats metal, major problem considering how many transhumans are partially or fully synthetic.
Tanaka: inhabited by ambulatory pseudo-fungi that attack anyone who comes through the gate.
Les Luthiers: in Ańoralgias, a nostalgic zamba about the composer's hometown. The final verses translate to "Hungry wolves howl in anguish while they're bitten by fierce mosquitos, you can't sleep from the cries of thousands of vultures that blacken the sky, there's always an ocassional earthquake, and at dusk it rains meteorites". And that's not taking into account stuff like the yearly 10-month droughts (which are interrupted by catastrophic floods), unbearable heat, and the near-constant eruptions of the local volcano.
In Marathon 2: Durandal and Marathon Infinity: Blood Tides of Ll'howon, the player visits the eponymous planet of Ll'howon under the command of the eponymous AI Durandal. The planet was covered mostly in vast marshes. However, the alien race known as the S'pht had turned nearly the entire surface into a city. After that, sometime around the 1800's, another alien race known as the Pfhor enslaved the S'pht, leaving behind only a few marshes and volcanoes (both full of hostile wildlife), along with crumbling ruins and the immense deserts void of life where these great cities once stood proud.
The world of Fallout features giant ants, murderous mutants with mini-guns, scarce food and radioactive water.
Fallout 3's Capitol Wasteland is the worst version shown so far. The ruins of DC are filled with homicidal mutants. The sewers are home to insane (and different) mutants. The outskirts are held by Raider tribes. On top of this, all food and water is radioactive unless put through time-consuming purification; the one source of clean water is being used as a delivery device for a bioweapon.
Even worse is The Pitt, from the expansion pack of the same name, where the industrial pollution combined with the heavy radiation has resulted in a mutagen that either disfigures its victims, drives them insane, or transforms them into the subhuman beasts known as Trogs, and those who are still human are either slaves or their iron-fisted masters.
Fallout New Vegas has the Sierra Madre Villa, blanketed in a corrosive red fog and inhabited by holographic ghosts and zombified hazmat workers, and the Divide, a veritable hell hole scoured by earthquakes and blistering, irradiated windstorms. Both were contributed to by the Mad Scientists of the Big Empty, and the Courier was inadvertently responsible for sealing the fate of the latter.
Chiron, a.k.a. Planet of Sid Meier's Alpha Centauri, has an environment highly toxic to humans and animals, predators (including aquatic and aerial forms) with Psychic Powers and Body Horror modes of reproduction and, incidentally, is semi-sentient and not very fond of humans or other unassimilated sentient thought. And then there's that whole "accidentally killing off all life on its surface every few million years" thing. It's actually a pretty nice place... while it's asleep. Too bad you show up when it's starting to come out, as it were, of REM.
Despite this, it's still better than Earth in its current state, considering those left behind nuked themselves to extinction shortly after the Unity left orbit. One of the endings has the Chiron colonists go back to Earth and clean up the radiation to make it livable again.
The planet Malta in Freelancer has Cardamine floating in the air; breathing that stuff is the in-game equivalent of breathing heroin. (It even gets into your genes, making the addiction permanent for you and all of your descendants.) In the same system, the planet Carinae seems idyllic, but its local biology is extremely poisonous to humans. Leeds, meanwhile, is so goddamn polluted their people lose their senses of smell and taste within 6 months, Pittsburgh is an inhospitable ball of sand and stone, while winters in New Berlin last an entire year and reach temperature similar to the ones in the Antarctica.
Still, these places are a walk in the park compared to one of the unlandable earth-like planets. Said planet is hidden in a radioactive nebula cloud, but the planet itself is almost ridiculously Earth-like, right down to having massive biodiversity. It's even described as a Paradise. It just has only one tiny problem regarding human settlement. All the life—both the animals and plants—have a chemical that's quickly and 100% fatal to humans. Humans wisely decided not to attempt colonization.
The Unreal Tournament 2004 Onslaught map simply called Red Planet is a weird hybrid. It's a planet without a sun, but the entire planet somehow radiates its own red light constantly. According to the map description, the effect drives a man insane within 18 hours. Thankfully (or not), you won't live that long...
The planet Kaduna 3 in the hybrid IF game Gateway is one of these. It has spiky plants whose spikes shoot at you if you as much as breathe at them, worm-like creatures that cling to you the moment you depart your ship and will gnaw your space suit off if given enough time, and other plants that grow so quickly that you'll die if you stay in one place more than a few turns. And then there are the spiders and snakes...
The game Elite II: Frontier came with the booklet Stories of Life on the Frontier, short novels set in the game universe. One depicted a group of game hunters visiting Bigg's World, a jungle planet where everything was vicious, deadly and/or poisonous. In an interesting twist, human proteins were even more poisonous to the native wildlife...
The krogan homeworld, Tuchanka, is pretty much one of these. The most common cause of death before the invention of gunpowder weapons was "eaten by predator". The krogan themselves evolved into one of the toughest, meanest, and most temperamental sapient species in the galaxy as a result. And managed to make their homeworld even worse. Let's not forget that the aforementioned "toughest, meanest, and most temperamental sapient species in the galaxy" is actually, judging by their eye placement, evolved from a prey species.After the invention of gunpowder, their most common cause of death became "death by gunshot", and it stayed that way once they got off their homeworld. Furthermore, when they were discovered by the salarians, they were in the grips of a nuclear winter with the last remnants of their race struggling to survive. Finally, once they were taken off their planet and placed in a safer environment, their population exploded, since without Tuchunka's many natural dangers to balance out their birth rates, they were impossible to contain.
A world in the same system as Tuchanka is even worse—a Venusiform planet. Most ships will get crushed if they don't have enough protection, and stepping out into the open is certain death - even for krogan. Regardless, it's something of a suicidal ritual to attempt to prove their manliness. Many krogan went out of their spaceships to the surface of the planet, deciding that if one of them survived, that'll be the sign of a real man. The number of survivors? 1!
How dangerous is Tuchanka? It's the only planet in the galaxy where the native life can threaten a Reaper.
Several of the planets visited in the game will kill you over time unless you're wearing a protection suit or stay in the Mako, and even a protection suit won't help in the worst places. Furthermore, some planets are inhabited by massive Thresher Maws easily able to chew through a shielded armored Infantry Fighting Vehicle in one bite. The same vehicle that can absorb quite a few shots from even the worst Geth energy weapons. Also subverted in a couple of examples: the planets have oxygen and are teeming with life, but the native microbes or pollen provoke deadly anaphylactic shock to humans.
The Dark World in The Legend of Zelda: A Link to the Past pretty much illustrates this trope — especially considering that if Link goes there without a particular artifact, he gets transformed into a helpless pink bunny.
Hyrule in general counts throughout the series, even the light world. A place where crows steal your money, setting ordinary bats on fire just powers them up, chickens are highly organized and vengeful unstoppable engines of ruin, and the flowers variously explode, shoot you with seeds, try to eat you, or sell you overpriced low-quality merchandise. And then there are the actual monsters.
The world of Balaho from Halo has an atmosphere of methane, suffers from two winters, and is subject to random geysers of fire popping out of the ground. Disease is also rampant, forcing the inhabitants to burn the bodies of their relatives as basically an everyday chore. Considering that this is the Grunt homeworld, you'd think they'd be a bit tougher for all this. Though there are many hints that they are actually pretty dangerous in their native environment; the fact that they have to wear heavy and fragile environmental suits anywhere else drops their combat effectiveness to basically zero.
SR388 Before Samus wiped out the Metroids (practically indestructible floating beings which can shoot destructive energy blasts and drain the life from any being they come across), they were the dominant lifeform on the planet (despite there apparently being only a few dozen of them) and any other creature had to be very strong in order to survive in such an ecosystem. After Samus wiped them out, the planet is taken over by a kind of shapeshifting bacteria (which the Metroids were the primary predator of) which most likely wiped out all other life on the planet, and prove a severe threat to human researchers (and eventually, the whole galaxy). Its very telling that Samus ultimately has to vapourise the whole planet.
SR388 hadn't even been given a proper planet name simply because it was so desolate, dangerous and just plain remote that nobody wanted to acknowledge it further. It's noted after the first game that Samus goes extremely out of her way just to get to the planet, nevermind the fact it hosts not one but two forms of life that, if left unchecked, could destroy the galaxy.
You spend about half your time in Metroid Prime 2 running around Dark Aether. Not only does the resident Hive Mind and its troops want to kill you, but the toxic atmosphere constantly drains your health unless you find a spot to rest in.
Zebes is a rather nasty place too. It's been described to be uninhabitable for normal humans (Samus was able to live there only because of being infused with Chozo blood, and even then she was only able to survive in the least deadly areas) and filled with miles of underground caverns crawling with all kinds of dangerous creatures. It got nastier when the Space Pirates conquered it, too (now the rain's acidic).
When Samus goes to Phaaze in Metroid Prime 3, her path to Dark Samus is not only covered with super tough baddies, but the atmosphere itself is slowly corrupting her. To top it off the planet itself is sentient.
The planetarium in Prime features some data on other planets the Space Pirates are intrested in, including one with radioactive dust storms and another inhabited by a Hive Mind created by a sentient and deadly virus.
The Pirate Homeworld, too. It is plagued by constant acid rain powerful enough to eat through the strongest of metal, and even energy shielding. All rock formations seem to have been melted away, and the only structures are very well shielded, making the planet appear to be completely metal. At the time Samus visits, it's also being transformed into another Phaaze by a Leviathan, and features giant pools of phazon and tentacles reaching up from the surface. It's clear from the beggining that this place is bad news.
Fable II has Wraithmarsh, a swampy region that's over run with Banshees and Undead. Ironicly, Wraithmarsh used to be one of the villages of the first Fable, one of the nicer ones, and the one where the Hero was born.
In Final Fantasy XIII the people who might have come into contact with the fal'Cie are deported down to the main planet Pulse, which is supposedly a Death World. Though it turns out they were just put on trains to the next death camp. Late-game, you travel to Pulse, and learn that while it's covered in very tough creatures, it's not as hellish and horrific as Cocoon claimed it was.
Gears of War's Sera seems like a fairly nice place....until you realize that underground it is coursing with explosive, mutagenic chemicals that cause terrible sickness in humans, and aboveground during the wintertime, it is quite common to encounter "razorhail," which are shards of glass-sharp ice pouring down from the sky and able to rip human beings apart and even damage tanks. And that's before you get to the Locust Horde and all the other assorted monsters roaming underground... On top of that, there's the Kryll. It's not known whether they are part of the the Locust Horde or if the Locust just control them. What is known is that they'll eat anything that comes into the darkness at night in seconds. Nighttime will kill you on Sera.
By the time of Gears of War 3,It's got worse. While the Kryll have been wiped out, it is now entirely possible for Lambent Stalks to erupt anywhere, spewing bioluminescent, homocidal mutants without warning (even over the ocean!). The surface-dwelling Locust have gone feral, killing anything they see. And to top it all off, Imulsion, the miracle energy source all the human tech runs on, is a parasite that is consuming Locust and humans alike.
Outland, the shards of a destroyed planet where the fact that it exists partially in the endless darkness of the Twisting Nether that gives demons their powers is the only thing sustaining gravity and an atmosphere. What with the Hellfire Penninsula, Netherstorm, Shadowmoon Valley, and Blade's Edge Mountains (where black dragon carcasses decorate the landscape, killed by the mountain-sized gronn), every zone here falls under this trope except the verdant Nagrand, creepy Terokkar Forest, and just-plain-weird Zangarmarsh (which is still full of fungus and predators).
There are parts of Azeroth that could probably qualify as well—Northrend is certainly one. Sithilus is dead, infested by silithids and qiraji. Felwood, and the Plaguelands (especially the east) are blighted, with the latter slowly recovering. The Burning Steppes, Searing Gorge, and Badlands are as pleasent as their names would indicate. Desolace and the Blasted Lands used to be nothing but wastelands, but are slowly recovering post-Cataclysm.
Killzone 2 reveals the Helghast world of Helghan to be a death world, with giant killer dust storms, air that goes from "nastily polluted" to "downright freaking acidic", lightning bolts with enough juice to destroy ISA armored vehicles...and then there's the Helghast themselves, who had to evolve into hulking, bald, glowy-eyed Neanderthals in order to survive in Helghan's environment. This was briefly discussed in the manual and cutscenes of the first game, but this is the first time we get to see first-hand just how bad it is.
Prior to Killzone 2 being made, this was a case of All There in the Manual as the Helghast world and the Helghast's struggle to adapt to it conditions was explored in more detail in an historical timeline on the official Killzone website.
The premise of Heavy Metal F.A.K.K.2 is that the planet is defended from invasion with a universally recognized beacon declaring it to be a Death World. And if you wander outside of civilization, that's exactly what it proves to be.
The setting of the Avernum series. An enormous cave system similar to the Underdark (see above). By the start of the series, several large caves are civilized enough to support cities. The First Exploration, however, found an underworld full of slithzerikai (savage lizard-people), undead, demons, and giant bugs. Part of the fun in the first game is to find the remains of the first explorers, all without fail dead in some corner of Avernum.
The planet your mild-mannered scientist character is teleported to in Another World (Out of This World in the US) is like this. The very first screen of the game features a sea monster that will pull you down to your death if you don't start swimming to the surface. The next creatures you encounter are tiny slug-like things which will slash you with deadly poisonous barbs if you get too close. And this is in the first minute of gameplay; it only gets worse from here.
Zoness from Star Fox 64 is a planet comprised entirely of machines and structures built on a toxic, acidic ocean that corrodes your Arwing. Also Solar from the same game, though that's justified in that it's a star. It's suggested that Zoness used to be a paradise before Andross' forces started messing with it.
Also from Star Fox is the appropriately named planet Venom. It's completely covered in yellow dust clouds, the oceans are acidic enough to melt a spaceship, the gravity is twice as strong as the other planets in the Lylat System, and plant life cant be found anywhere. Sending Andross here in exile was thought to be the Cornarian equivalent of a death sentence.
Wild ARMs has the numerous incarnations of the planet Filgaia. While its level of Death World-ness is variable, it is always a steadily degrading world that's mostly unfriendly, if not downright hostile to human life, usually thanks to environmental catastrophes or wars. Wild Arms 3's Filgaia is especially bad, as all the oceans actually dried up (there's nothing but endless sand formations left, which strangely behave a lot like water), water is awfully rare, nasty flora and fauna are everywhere, there are titanic monsters running around some locations (including one that systematically attacks anything that goes faster than a horse in its territory and wrecked many trains already) and several ingame sources hint that the environment is too far gone for anything to help: even nanotechnology is useless by now.
The Wasteland from Billy Vs SNAKEMAN is an expanse of Death World made of ninja villages blown up by the sheer awesomeness of their leaders. The safest parts of even the outskirts of The Wasteland can be described as "Like the Sahara but the sand is poisonous". Near the center, sunlight occasionally spontaneously focuses into a laser, homicidal unicorns are perpetually searching for new victims, and the corn will eat you if you're too slow.
While most of the Ages of the Myst game-series are liveable, Age 233 (where Gehn's office is) is a rather nasty place, with caustic oceans that have deeply eaten away the mountains up to high tide level. Selenitic is geologically unstable and has suffered some nasty meteor strikes in the past, and one false step in Spire will send you plummeting to your death in the fires of a green star. Riven becomes one at the end of the eponymous game. The Expanded Universe of the novels describes how Ages which haven't been visited in centuries have been known to turn into Death Worlds in the interim, forcing one of the Guilds to send scouts to check out such places in full-body protective armor.
Char is a Single-Biome Planet of volcanoes, which the Zerg have come to call a de facto homeworld. One soldier reports that "the planet itself joins in the killing".
Zerus, the real Zerg homeworld, was very similar when the Xel'naga first got there, but by the time we see it, it's a lush jungle world. Filled with Primal Zerg organisms that have spent the intervening millenia fighting each other and evolving. And unlike the Zerg under the Overmind, they don't have a Hive Mind—each and every Primal Zerg is a sentient, sapient predator dedicated to killing and evolving.
Days that are 90 hours long, seasons that are 7 years long. The planet was first discovered and settled in the winter, and everything seemed to be going fine for the first couple years. Then spring rolled around, and all the hibernating animals started waking up.
The multiple wholly unique species of extremely omnivorous creatures perfectly willing, and capable, of bagging humans. Included are the skags, which are dog-like creatures that live everywhere on the planet and can eat nearly anything. There's the rakk, which are predatory avian/bat-like creatures that swarm prey on the ground in massive numbers. Spiderants, which live in massive colonies and have armored exoskeletons capable of repelling gunfire. Plus the stalkers, a species of predator who can turn invisible, fling spikes at ranges comparable to sniper rifles, and have organic shields. There's also the varkids, which are insects that can rapidly mature from small, easily-killed larvae to massive flying tank-like horrors. And worst of all, there's the threshers, a species of massive, subterranean serpents with long tentacles that move with terrifying speed and can attack from any direction. This is not counting the presence of the Vaults, whose ancient alien technology gives the local wildlife elemental properties, so any of the above could be covered in electricity, breathe fire, or shoot acid. The only creatures that weren't immediately hostile were the crystalisks, which were implied to be sentient lifeforms, but they turned on humanity with a vengeance when the Dahl corporation tried to "mine" them.
There's also intense heat and horrendous weather, along with schizophrenic climate that includes a completely frozen area with active volcanoes. The opening of the first Vault made this even more violent and chaotic, to the point that hydroelectric dams literally froze overnight.
And humanity made it worse, with a population of untold numbers of angry, mutant, or simply insane criminals and bandits, all armed to the teeth. Not counting tremendous environmental damage even before the first Vault was opened, causing the rampant growth of Eridium across the surface. It doesn't help that it's all but confirmed that Pandora's Eridium can and will drive people insane.
The local plants get in on the act as well. One inhabitant experimented with rolling herbal cigars from the local flora. The result? Death from massive internal bleeding. The obviously lethal plants include electric cacti and firemelons.
The S.T.A.L.K.E.R. series (which Death Zone above spun off of) features the real life Chernobyl exclusion zone... which, thanks to Soviet Superscience (more specifically, an attempt by a group of Soviet scientists to use all of humanity's mental energy to be formed into one, to end all suffering and conflict and Alternate History (the experiment came in the 90s, using the abandoned Chernobyl area to conduct research in peace), has been morphed into a highly radioactive wasteland, where psychic storms that fry your mind occur on a daily basis, powerful mutants (some who can kill you with their brains) rip the inhabitants to shreds, The Mafiya and various thugs crawling everywhere to rob and murder anyone in sight, the Military, who are essentially bandits with superior tech, rips and tears in space-time called "anomalies" that defy physics - ranging from raging infernos, moving bursts of lethal eletricity, being tossed several feet into the air, being trapped for all eternity in a localized bubble of one moment, extremely acidic goop (some of which hides in the ground and doesn't pop up until it's too late) that chews through metal like nothing, and gravity itself picking unwary men up and tearing them apart mid-air. On top of that, well-armed militant fanatics who worship the Zone shoot up and kidnap what the Bandits and Military don't get to - and if they don't kill you, the chance of being caught in the crossfire between two armies, one who want the Zone to be open to all to improve human technology, and one who want it destroyed and sealed, will. Welcome to hell, Stalker!
The various Pokémon regions, where bugs the size of car tires are the norm. People in the Pokeverse say that traveling without a Pokemon companion of your own is dangerous. They are not joking.
Even in a Lighter and SofterDeath World like the Pokeverse, Pokemon Colosseum's Orre stands out in particular. First, it's based on real-world Arizona, which neighbors hellish California and Nevada. So, natural desert is the majority of the landscape. Second, if you think humans have it bad, wild Pokémon in Orre are said to be rarer than water, and that's saying something given that the only flowing water in the Eclo Wastes is in Phenac City and Agate Village. Third, the place is a Wretched Hive with the criminals in charge, and Cipher is top dog. Isn't it fitting, then, that the most Badass protagonist in the history of the series happens to come from this very hellhole?
Discussed in Ultima Underworld II. When speaking to Iolo about the worlds beyond the blackrock gem, he expresses concern that one of the gem's facets could lead to an ocean floor or a planet of poisonous gases. (It doesn't.)
Total Annihilation has a few: Barathrum (named after a Latin word for Hell) is Lethal Lava Land, Kral is covered in seas of acid, and Core Prime is a sterile metal-covered world inhabited solely by thinking machines.
The Deep Roads in Dragon Age: Origins are pretty awful thanks to the literal Demonic Spiders, the Deepstalkers that erupt from the ground en masse without any warning, the hostile ghosts and out of control Golems in the lost thaigs, and Darkspawn. Lots and lots and lots of Darkspawn. Everywhere. Even if you somehow evade all of those, the only way to avoid starving to death is to eat Darkspawn flesh since nothing else is readily available. Assuming the Taint doesn't kill you outright, this will turn you into a Ghoul. Then you'll die in a few years anyway thanks to the Taint. In the Dwarven Noble Origin, the death penalty applied to you is being sent into the Deep Roads with nothing but a sword.
Parts of RuneScape, and a few dimensions that can be gotten to with portals from RuneScape, are Death Worlds:
The Wilderness, with all its volcanoes, dragons, haunted graveyards, evil spirits, and absolutely everything trying to kill you. To make matters worse, it's a player-versus-player area, and player-killers can be even more deadly than the monsters.
The Gorak's Plane that was visited very shortly during the "Fairy Tale, Pt. II" quest, which is a Pocket Dimension populated entirely by powerful, vicious monsters.
The God Wars Dungeon. Imagine a huge open space with dozens of deadly monsters running around, protecting insanely powerful bosses with powerful bodyguards. Even some of the most experienced players tend to avoid that place.
City of Heroes has the Shadow Shard, four zones of floating rocks, populated by a conglomeration of minor Eldritch Abominations and spirit-replicas of all the baddies that you already hate to fight, all in the service of a demigod who eats universes. The main means of travel are "Gravity Geysers" that launch you from rock to rock, and should you happen to miss your landing site, you will fall to you death and have to start again at the beginning of the zone.
And now, in the backstory of Going Rogue, we have Praetoria, an alternate Earth where the majority of the planet has been taken over by the Devouring Earth, led by the Hamidon. By part-scientific, part-magical means, Hamidon caused The End of the World as We Know It, by causing the Earth itself to literally rise against humanity. The player can't actually leave the safety of the city of Praetoria, but apparently, should you leave, the rocks, trees, and fungi around you will literally come alive and kill you.
The eponymous planet of Kalevala in Legend Of Kalevala is brimming with biomechanical creatures that are all trying to kill the protagonist, pits of lava and acid, and all sorts of spikes, bombs, and other hazards. Turns out it's only a Death World for the protagonist; he is inhabiting the body of a Kuririi, which everything on the planet has been programmed to destroy.
Don't let the colorful, 2D graphics deceive you—the randomly-created worlds of Terraria are Death Worlds, one and all. Killer slime can be found in the safest environments. Vultures, sharks, hornets bigger than you are, killer bats, and even piranhas await you above ground. Razor-sharp feather-slinging harpies inhabit the upper atmosphere. The underground is filled with skeletons, killer roots, vampire bats, and far enough down, demons. The hills and caverns are steep enough that you can die from fall damage just by traversing the terrain, not to mention the risks of drowning or falling into pits of lava. Meteors and Hellstone will burn to the touch unless you've built a charm to ward them off. Legions of zombies and enormous, disembodied eyes will pound at your door all night, every night. Eventually, an army of goblins will descend upon you with little warning. And every night has a chance for the Blood Moon to rise, increasing the number and might of the zombies, and turning even the harmless bunnies of the wilderness into walking horrors.
The first instructions you get upon starting the game are on "surviving your first night."
Similarly, Minecraft can easily be regarded as a Death World. Sure it's pixelated and only domesticated farm animals seem to be the most of your troubles at first, but once the Sun sets or you start exploring you realize this seemingly serene world is trying to kill you in every way possible. The terrain is littered with random cliffs, deep drops and pits of lava one could easily kill themselves in and random forest fires happen a lot. At night armies of undead zombies and skeleton archers along with kamikaze creepers and gigantic spiders will track you like heat-seeking missiles if they see you while the almost 3 metre tall Endermen will wipe the floor with any unprepared player does as much as glance at them. Meanwhile booby trapped ruins experiment with different ways to creatively end you; from housing nests of huge poisonous spiders to being able to blow you and all the treasure to bits or having tripwires primed to shoot any trespassers. Even seemingly "safe" mobs like the wolf will descend upon you in packs if you hurt any even by accident. It even has the Nether; it's version of Hell, home to it's own collection of death-toting enemies from huge fire-shooting Eldritch Horrors to 2.5 metre tall sword-welding skeletons that will cause you to literally wither away. At least with a Hell you'd think there would be a Heaven right? WRONG. It's just another Hell, where bottom void surrounds the one tiny island and Endermen are everywhere; if that's not enough there's also an almighty dragon that kills anyone on the island.
And if you are playing on a server, sometimes other players will be yet another thing you have to avoid if people are after you for your blood and gear.
Dwarf Fortress, where just about every moving object tries to murder your dwarves. This is especially true in evil biomes, where lasting more than a few in-game years against the undead hordes and disease-spreading weather is an accomplishment.
Planet Ortega in Space Quest III requires wearing special underwear to survive the intense heat.
There are only three planets in Space Quest V that require you to beam down onto the surface as part of the storyline. Of those three, one of the planets has a toxic atmosphere requiring the use of a rebreather. All of the other planets in the game have conditions so hostile that you will die immediately upon beaming down to them.
Escape Velocity Nova has Cunjo, named for its top predator. Auroran warriors sometimes hunt them for bragging rights, and rendered a minor Federation world unsuitable for colonization by introducing cunjos to it.
The Auroran capital worlds also qualify: ridiculous levels of pollution from extreme overpopulation makes them uninhabitable outside of arcologies.
Really, most Role Playing Games qualify. Need to go to another city or town? Or just need to visit the countryside? Better be ready to fight off ambushes by bands of monsters and human marauders. No wonder every village, town, and city has weapons and armor shops!
The dying world of Eltria in Magical Girl Lyrical Nanoha As Portable: The Gears of Destiny, where the lands are desert-like, the waters are contaminated, and giant, rampaging monsters roam everywhere.
Naev's backstory has Sorom, which kept killing off its inhabitants by progressively worse plagues that eventually culminated in the Empire quarantining it. The Soromid only survived because of a breakthrough in LEGO Genetics that allowed them to augment their immune systems. Then Sorom was caught in the blast from Sol blowing up.
In Quentyn Quinn, Space Ranger near the galactic core lies the homeworld of the Kvrk-Chrk. In addition to having extremes of temperature, gravity, pressure, radioactivity, etc. that would be immediately lethal for most other lifeforms, it has a biosphere so aggressive that the natives have to eat their food still alive and kicking in order to ingest it before necrotic parasites do.
Then there are the Kvrk-Chrk themselves, who consider awake and screaming a FLAVOR, have carapaces that would put a tank to shame, and can rip any other species to shreds effortlessly. The aforementioned extremes on their planet makes them essentially immune to all but the most extreme forms of weaponry (and even the most extreme might only annoy them briefly). Among their other quaint customs is, when visiting a neighbor, ripping off one of their own limbs to offer as a snack. They also consider all other intelligent lifeforms "chatty food". They once declared war by taking a defenseless colony ship and brutally butchering the crew, then broadcasting recordings of the slaughter on all channels, promising that this would be the fate of every other species in the galaxy. The only reason they didn't wipe out the competing empires is because they found out the hard way that being unparalled engines of annihilation on the ground doesn't help too well when the guys you're fighting against can annihilate entire systems with a single shot from a stellar lance several lightyears away.
Alternia. This is a world whose inhabitants are nocturnal because zombies wander around during the day. This is a world where the fauna are so vicious, 13-year-old children are expected to be combat-capable. This is a world where the only significantly large body of water is inhabited by a very large thing that must constantly be sacrificed to to prevent it from using its psychic powers on the whole populace. This is a world that serves as the training ground for a Proud Warrior Race that practices The Spartan Way. Thankfully, the protagonists from Alternia are sufficiently Bad Ass.
And then there's Eridan's planet, which is even worse. Between all of his consorts going on a homicidal frenzy, and Eridan shooting anything that moves, even the most hardened Bad Ass trolls were afraid to set foot on the Land of Wrath and Angels for more than a few moments.
Invoked and/or Downplayed in TwoKinds. One character's homeland is an (presumably volcanic) island chain so brimming with toxins that his people are immune to most known poisons and diseases.
Tech Infantry has both Fieras VI, a fairly unpleasant world in terms of climate, terrain, and biosphere. But then there's the aptly-named Soul Eaters, alien life forms that possess humans, grant them Body Horror-based supernatural powers, and eventually totally take over their minds and convert them into new Soul Eaters. On top of that, the planet has a screwy magnetic field that interferes with electronics, especially targeting systems, so you can't even nuke the planet from orbit. There's also the prison planet in the R45 system, whose landmasses are mostly swamps overrun with poisonous plants, nasty predators, carnivorous plants, and stranded alien bugs driven insane by the planet's natural anti-magic field. A planet that drives BUGS insane is not a nice place to serve out a life sentence, however brief that may be.
Felarya (NSFW), except everything is trying to eat you. Or just kill you. Or, you know, both. The writer specializes in vore, so, as expected, most of the flora and fauna in his magnum opus are based on one question: "How many ways are there for a creature to eat someone?" There's a creature for every possible method. How about gassing you and growing roots into you to suck out the juices? Or portals out of that hell being created by creatures who live between dimensions and will snatch you while you're in Subspace Or Hyperspace for dinner? The ones on the low end of his hazard scale aren't safe, they just need to be near you to kill you as opposed to, say, creating a wind tunnel to suck you up from over a hundred yards away. It's amazingly creative. However, if you're not a voreaphile, the sheer number and creativity of ways you can suddenly find yourself in something's gut make it scary, not sexy.
It gets better. He has most of his critters forgo the whole 'chewing' bit even when they've got big teeth. When - not if, when - something in Felarya makes a meal of you, you don't get to die quickly when the jaws close, no. You get a nice acid bath that can take days to finish burning your flesh and bones down to nothing. When the only mercy a world has is that if you're lucky, you run out of oxygen before you can suffer too terribly, you know you're in a Death World.
That Guy with the Glasses' version of General Zod plays up Krypton's canonical deathworldiness. Apparently, apart from anything else, the acid rain melts heads. And the beverage of choice is uranium slurry.
The native life of Green Antarctica is just plain nasty. There are the Gugs, murderous, raping gorillas, there are ants that shoot fire, giant platypus that have evolved convergently similar to crocodilians, a kind of small mammal who's bite sends humans into comas, and then eats them alive, and countless other disturbing animals.
Spec World, an alternate Earth where giant killer dinosaurs still live.
To give more information there are many dinosaurs that are almost overly dangerous with Names to Run Away From Really Fast like the Ninja (black raptor that often rips peoples' heads off for no reason), the imperial sabre Tyrant (tyrannosaur with sabre-teeth), or the black beast (Africa's largest and meanest predator).
Also there are a lot of dangerous not-dinosaurs like the Terrorsaurs (no points for whoever guesses those evolved from), the large variety of crocodilians (cruncher-crocs, croclions, croc-tigers, jagators, cuttercrocs etc.), the mosasaurs (carnivorous aquatic-lizards such as the leviathans, the mosarks and the lizardwhales), ultravipers or featherboas (both incredibly venomous large snakes), or gobblers (it's version of terror birds) that really want to kill people.
Even the soft and fuzzy mammals of the Mesozoic have been abandoned for vicious and dangerous new ones such as the baskerville (glowing canine-like member of the possum-hounds), Digga-dumdums (large burrowing animals that can use their claws to rip up the face of even tyrannosaurs), the powerpus (large bulky platypus with fangs), Moby Duck (multi-ton marine platypus relative), the unrats (primitive mammals with venom so potent not even the hungriest gobbler would eat them), or the tree foxes (primates with sharp fangs and retractable-claws).
Unicron would be an example of the Genius Loci variant. His outside is mainly devoted to consuming other worlds, and most of his inside is devoted to killing anything that made it in alive with tentacle, spikes, vats of acid, et cetera.
There are even some continuities where Cybertron is depicted as being hazardous enough in itself. The IDW comics make a point that their war had caused the planet to become completely uninhabitable for centuries (And when we say "uninhabitable", we're talking for a race of Humongous Mecha). When they finally are able to make a temporary base there, the planet is overrun by monstrous Insecticons that tear apart and devour any Cybertronians they come across.
There's there's one comic (based on an alternate future to the live-action movies) where Unicron makes Cybertron itself his new body.
Invader Zim makes an offhand reference to such a place:
Almighty Purple: Zim again. We really should have sent him on a mission to a sun, or a planet of broken glass. Almighty Red: Or one of those exploding head planets.
There's also Hobo 13, the military training planet. It's a barren wasteland inhabited by deadly predators and covered all sorts of other hazards. The Tallest send Zim there to get rid of him and immediately open a betting pool on how long he'll survive.
Parodied in Futurama; there's a sector of inhabited space called the "Death Zone", but it's just a name, like the Forbidden Zone, or the Zone of No Return. All the zones have names like that in the Galaxy of Terror.
The original movie-length pilot episode opened on an unnamed planetoid. The atmosphere isn't thick enough for humans to breathe... which is arguably a good thing because it's deathly poisonous. It's also infested with Crater Vipers.
Third Earth, on ThunderCats, has such charming locales as the Phosphorus Desert (where the sand can burn the flesh from your bones with a mere touch), the Crumbling Cliffs of Vertigo, and the Field of Daggers. There's theories it may be humanity's Earth in the far future — if so, no wonder there don't seem to be many humans left.
And there's the wildlife, from the black widow shark to earthquake-causing caterpillars. The resident races are interesting, as well: giant stone golems, crab-clawed men, giantors... and those are the low-risk ones.
In one episode of the nineties Fantastic Four animated series, Terrax tricked Galactus into devouring a world so awful that it poisoned Galactus.
Rainbow Land is this before Wisp saves it. Giant monsters are everywhere including the rivers. There are constant earthquakes resulting in rock slides and lava flows. Oh and if you try to get close to the Evil One'scastle? Lightning strikes you and turns you into an ice/crystal statue.
The Realm in the old Dungeons And Dragons tv series. Not EVERYTHING was trying to kill the heroes, but most things were, including at least two beings operating on the deity level (one would attack them incidentally, the other was actively seeking to harm them). Most people with significant power were hostile or so totally preoccupied with their own problems that they couldn't help.
The world portrayed in The Croods is so dangerous that the Croods only dared to leave their cave once every three days or so to look for food. Gigantic man-eating cats, snakes that could swallow entire families whole, swarms of carnivorous birds that could strip a land-whale to the bone in seconds, and then it gets worse when the fissures start opening into chasms of lava.
...depressingly, it doesn't kill the Cane Toad off or Rabbits or Foxes strangely, which are harmful to even AUSTRALIA'S extreme biosphere.
The Amazon Rainforest was here; you're all small-time. Damn near everything from the plants to the bugs to the water is actively trying to kill you.
The highlands of Papua New Guinea. It's not TOO bad if you know what you're doing (like the locals) or have their help. However, the Japanese tried going through it to capture Port Moresby after their invasion fleet turned back after the Battle of the Coral Sea. An estimated 75% of their forward fighting troops were killed, wounded, or became ill, and over 60% of the total force didn't make it back to their starting point.
Ilha da Queimada Grande, a small island off the coast of Brazil, and crawling with very deadly Golden Lancehead vipers—as many as 1-per-square-meter if averaged out.
South America's Atacama Desert is so arid that not even bacteria can live there.
Antarctica. At least Australia has a permanent human population. And the interior of Antarctica doesn't permanently support any life. Emperor penguins live there part of the year to breed and raise their chicks, and the males (who stay there the longest) lose half their body weight doing it.
On a related, but much smaller, note: Mount Everest. If you're a strong-lunged mountain climber, you'll need an oxygen mask to avoid losing your mind in the thin air and walking off a cliff; if you're a regular person, you'll suffocate before you can get the mask on. It's also got unpredictable snowstorms, and if the cold doesn't kill you, it'll freeze your toes off—literally. Have fun!
Even Mount Everest is small potatoes compared to K2. Part of this is due to geographical conditions: whereas Mount Everest has routes that properly acclimated and equipped amateurs can use to ascend, climbing K2 is very technically difficult. In general, any altitude above 8000 meters on Earth would qualify as a Death World, as the atmosphere is so thin that there is not enough oxygen in the air to permanently support human life.
Russia. Certain regions of it are suprisingly mild as Death Worlds go, and Russians themselves find these spots rather nice to live in. However, most of it (the taiga, the tundra, the swamps) is a bona fide Death World featuring deadly frosts (Oimyakon, the Northern Hemisphere's coldest place, is here), literally man-eating swarms of vampiric gnats and huge bears (the Siberian brown ones are the size of American grizzlies, Kamchatkan ones are the size of kodiaks, and we don't even get started on polar bears) that do not fear man at all. And swamps, lots of them. Food comes from hunting and fishing, because this is permafrost country and no agriculture is possible. If that wasn't enough fun, the blistering summers are still there. It's called severely continental climate, and it's all about extremes. It's either hot as hell or cold as hell a thousand years before the Devil started the fire there.
The North Caucasus region of Russia is a place that has long been affected by widespread violence (both criminal and political), corruption, terrorism, kidnappings, lawlessness, and poverty. Currently considered a ongoing war zone most governments have placed this area high on the do not travel list.
There's a reason why the end-Permian extinction is called "The Great Dying". 90% of all life on earth went extinct, including the top predators, Gorgonopsids.
For any humans it's likely the Mesozoic era. Obviously there would be dinosaurs everywhere but there are also many more dangerous wildlife like terrestrial crocodiles, giant pterosaurs, large venomous lizards, fresh and saltwater aggressive fish, toothy birds and large dinosaur-eating amphibians to name a few potential threats found during the age of reptiles.
New Mexico has a stretch of desert called "the Jornada Del Muerto," i.e., The Dead Man's Trail. This is a chillingly lifeless hundred-mile desert trail completely devoid of life and water. Before the rise of the automobile crossing the Jornada was frequently deadly; when conquistadors from New Spain discovered it they named the first pueblo they found on the other side "Socorro" - Spanish for "help." In 1945 its lifelessness was confirmed when it was used as the test site for the world's first atomic bomb.
Africa. It's the only place where a menagerie of large mammals still remain, the heat is very intense, there's an outbreak of all kinds of diseases, and it's home to the most dangerous snakes on Earth.
On a related, albeit tragic note, this would also hold true for most long-lasting civil wars, especially in the 20th century and especially in Africa. One example would be Sierra Leone with it's marauding, drug-crazed, limb-amputating bands of RUF rebels, and the governement troops relying on "tactics" that are sometimes just as gruesome. Things supposedly have become better till the late 90s, though. Then you watch the news and see what's going on in Ciudad de Juarez/Mexico...
Venus is certainly the best example of the trope in our solar system. The atmosphere is almost entirely carbon dioxide, the sky is constantly overcast with clouds of sulfuric acid, and the global climate is in excess of 500 degrees Celsius. All probes sent to Venus were quickly destroyed by the heat, or crushed by the air pressure, which is about ninety times that of Earth's at sea level. Scientists have called it Hell, and with very good reason.
Which makes it strangely fitting that this is the planet the Devil takes his alleged name from. (Venus = Morning Star = Lucifer.)
As for how it could possibly remain named after its namesake, the goddess of love and beauty, one might utter the saying, "Hell hath no fury like a woman scorned."
Really, the rest of the Solar System is no picnic either. Mercury is so close to the sun, the surface is obscenely hot. Mars and the Moon alternate between being colder than Antarctica and hotter than the Ethiopian desert. Jupiter has storms the size of nations swirling about its surface. Saturn, Neptune and Uranus all have constant storms that are stronger than any hurricane on Earth, and none of the gas giants have any solid surface. On top of that, none of them have a breathable atmosphere. There's a reason some scientists call Earth "the miracle planet".
Speaking of carbon dioxide, living near note within 16 miles ofLake Nyos is quite hazardous given its nasty, if occasional, habit of belching 1.6 million tonnes CO2.
The scary thing: Lake Kivu has the same problem, is 2,000 times larger, and sits right next to a rather densely-populated area, including the major cities of Goma and Bukavu (with populations of about 1 million and 750,000 respectively) right on its shores.
Considering that the Kivu area has a habit of revolting, one rather wonders if the leaders of the Democratic Republic Of The Congo morbidly half-wish that the lake would just blow up tomorrow.
The Vile Vortices, a group of places in the sea with an unusually high rate of ship and plane disappearances.
Ramree Island in Burma is home to thousands of saltwater crocodiles, malaria-carrying mosquitoes, and venomous scorpions. During one battle of WWII, 1000 Japanese soldiers entered, and only 20 made it through alive.
The North Yungas Road in Bolivia. In English, that's "North Road of Death".
The Chernobyl Exclusion Zone is actually a subversion. While most people avoid the ruins of the city like the plague because of residual radiation, the flora and fauna have flourished in the decades since the meltdown and initial die-off from the fallout.
There is a small staff on site to carry out ongoing monitoring of the reactor's containment and the effects of the event. While suitable protective equipment and precautions allow people to live and work in complete physical safety, the same cannot be said for the effect on their minds. The staff has a quite high rate of various forms of insanity. There was a public address system built to pipe music into the area constantly to reduce the sheer mind-breaking creepiness of a completely abandoned city.
Outer space. There is nothing organic that can survive for long in the vacuum. Unshielded, vast amounts of radiation will kill any human, and if that doesn't do the trick, will leave unpleasant mutations and other fun surprises in the body - and that's if the temperature doesn't do you in. Depending on how close to a star you are, wherever the sun hits can be hot enough to just flashboil your flesh off - and the shade isn't any better, as it'll be well below freezing. Meteorites and other flying objects, often moving at speeds that make fighter jets look like snails, can ram into flesh. The lack of pressure will cause organs to swell and burst. And if asphyxiation doesn't do you in, the lack of gravity will warp bones and muscles into being useless after a while.
The ocean. More than half the life on the planet lives in the water that covers over half of it's surface, and most of it is predatory. Coral reefs full of venomous creatures, where octopus and moray eels lurk within crevices, where the coral itself can kill. The open ocean is a realm where almost every animal is both a predator and a prey item, where they have to keep constantly moving, because staying still for even a moment can get someone eaten. Tidal pools, where stranded creatures eke out a living in an environment where the water they need to survive can drain out overnight. The deep oceans, utterly devoid of sunlight, as cold or colder than the coldest temperatures on the surface, exuding enough pressure to crush a human body several times over. Where animals have evolved to eat whatever they bump into, and traveling more than a few feet up or down could mean instant death. For a good illustration of just how hostile the ocean can be, just look to what happens when there is a bloom in the krill population in a specific area of the ocean.