Help coming up with an apocalypse no one could have predicted

[LibraryOgre]

Some irresponsible lout dumped some brown mold into the elemental plane of fire, and now it's turning into the elemental plane of brown mold.

That is diabolical. I'm gonna ask grognards about this one.

[brian 333]

That is diabolical. I'm gonna ask grognards about this one.

It mutates into Orange Mold, which is a pyrophillic organism. Orange Mold absorbs fire damage and heals its injuries. Any area which has a fire damage per round penalty grants the mold a like amount of growth per day. When the mold is twice it's normal size it undergoes fission and becomes two molds.

When it is in the radius of an area of effect fire spell, it reduces the severity of the attack for all possible targets of that spell or effect by its current HP, (before calculating any healing the spell may offer.)

[Nagog]

Is this apocalypse supposed to be more of a "The world will soon end" type apocalypse, or just a radical and almost extinction level change happening worldwide?

[KineticDiplomat]

All magic has converged into a single globe spanning stormfront, and now races across the world like a stormfront that circles the world about once a year. Getting caught in the storm is horrific chaos and destruction, but immediately behind it is a zone where magic is bountiful, powerful, and easy...but as the storm slips away, it slowly fades to nothing until eventually you're at a point where everything is straight mundane, or even law-of-nature hostile to magic. Until the front hits again next year...

[Bohandas]

The constellations are disappearing and as each one goes the people born under that sign start dying bizarre Final Destination-style deaths (inspired by the short story Run The Sky)

Also, the thread D&D supernatural phenomena may be of interest

[Laserlight]

I've always wanted to run a game in which the sun has gone out and the only way to get "sunlight" is to magically burn gold. Burning silver gives you moonlight, which is enough light for you to walk around safely but not to grow crops. Burning copper gives you warmth, which is nice, but almost no light.

Every day, the priests light up a small pile of gold in the center of the fields, and the crops grow. As long as you have enough gold...

[NichG]

It turns out that there's an arbitrary combination of syllables that is the name of an eldritch creature who senses and hunts those who have ever thought that sequence through dream. Upon hearing or thinking the sequence, within a week a person disappears without a trace in their sleep.

Dreamcatchers, certain REM sleep modifiers, etc can provide protection. Maybe. So can memory loss drugs.

Someone transmits this sequence during a heavily watched and retransmitted TV event, or it becomes a meme on online social media sites, or otherwise not only hits a quarter of the population but gets recorded in a form that you might risk stumbling on when looking for information like 'where did everyone go and why?' or 'what do we do now?'.

[Beelzebub1111]

You could take the Wightpocolypse scenario to its conclusion. a nation where all the common folk have been killed and tuned into wights themselves all subservient to a single wight. the only people left are the heroes strong enough to fight back, but that's just a handful against hundreds of thousands. Everywhere is hostile, nowhere is safe to rest. your players are in the thick of it trying to escape and one wrong move will bring the storm down upon you.

[brian 333]

The Fungus Among Us

Giant mushrooms began to sprout, and rings of them grew, casting spores about the size and shape of a chad from a paper hole puncher. Ordinary fungicides did little to stop the expanding rings of mushrooms, and wherever a spore landed, new rings form after a few weeks or months. Field, forest, even deserts failed to stop them, though, for now, it appears that ice slows their growth down.

Scientists concluded that rhizomes in the soil thread through living or dead matter extracting their nutrients. Those same scientists later discovered that contact with even a microscopic shard of rhizome allows the fungus to propagate through the body of a host. Most animals are now infested with the fungus, and when the rhizomes grow enough to produce fruiting caps the host dies.

As the plague progresses, the glaciers and ice caps and the salt-seas offer what refuge there may be. But someone has to stop this! Someone has to find a way! As food sources dwindle and starvation takes over,it is only a matter of time. Years? Months? Days? (Are you already infected?)

[rel]

I've always wanted to run a game in which the sun has gone out and the only way to get "sunlight" is to magically burn gold. Burning silver gives you moonlight, which is enough light for you to walk around safely but not to grow crops. Burning copper gives you warmth, which is nice, but almost no light.

Every day, the priests light up a small pile of gold in the center of the fields, and the crops grow. As long as you have enough gold...

Cool idea! If burning gold also keeps monsters at bay, you can have safe towns in perpetual spring / summer, with deadly wilds in the grip of eternal winter in between.
Lot's of nice symbolism equating autumn and winter to death, and plenty of good reasons for adventurers to be out and about, be it trade, relief to a beleaguered town, diplomacy, or just delving into the deep places beneath the earth for enough gold to hold back the night.

[Bohandas]

Midas/Grey Goo- Either due to a king midas type character walking around barefoot or an alchemical philosopher's stone experiment gone wrong there is now a rapidly expanding zone where everything has turned to gold

[Yar]

Mimics have started reproducing at a shockingly alarming rate and are more intelligent. You can't even trust that any sort of object won't try and kill you society crumbles, paranoia rules the age of mimics has begun.

[Bohandas]

Some sort of thing that drains the individuality and joie de vivre out of everybody, like the Blue Meanies from Yellow Submarine of the evil feathers from Preeny Has to Repeat the 6th Grade

[Gazer]

I am planning on using this one but feel free to use it if you need to.
Invasion of the far realm: the setup is that the main protecter deity of your pantheon snaps and decides that the only way to protect everyone is to go on a series of crusades against the (insert plane hear) which ends in them becoming an elder god. I’m using Tyr and having him go to the far realm and becoming Tyranny. There are a lot of ramifications you can play with like having all his paladins and clerics becoming warlocks and cultist and having the portal flooding with extraplaner creatures (in the far realm example having it be mindflayers, beholders, and miscellaneous aberrations)

[Millstone85]

Invasion of the far realm: the setup is that the main protecter deity of your pantheon snaps and decides that the only way to protect everyone is to go on a series of crusades against the (insert plane hear) which ends in them becoming an elder god. I’m using Tyr and having him go to the far realm and becoming Tyranny.

A truly misguided plan in both of my interpretations of the Far Realm:

• Option 1 -- The Far Realm is the larger multiverse, or the space between the Great Wheel and other cosmoses, so it is like a bubble fighting the ocean.
• Option 2 -- The Far Realm is the edge of all existence, populated only by the distorted reflections of whoever makes the mistake of approaching.

[Grim Portent]

What about a Mass Psychogenic Illness event?

Like say the majority of people just stop communicating, no talking, no writing, no sign language or anything. They just make animal noises at each other, like meowing, barking or mooing. The breakdown in communication between people causes society to collapse, as the minority who are still able to converse can't care for all the others. Unable or unwilling to communicate the afflicted wind up resorting to theft and violence to get things they need from one another and the unafflicted, some form gangs or packs and a crude heirarchy to cooperate on such efforts. In general the afflicted rapidly degenerate into a violent hand-to-mouth existence. They are still perfectly capable of using tools, clothes, technology and so on, just completely incapable of using or understanding language of any kind.

Perhaps multiple forms of MPI happen all at once, and in some places lots of people started spontaneously dancing until they died, hallucinating and other similar things, resulting in mass deaths and panic before the main collapse happens.

[Herbert_W]

I think there's two reasons why your first apocalypse worked so well.

First, it takes the ground out from under people's feet - which I mean metaphorically, although it also happens to be true literally. You've taken something that people can rely on - something that's so basic that we don't even think about it, which in this case is literally "there's ground under our feet that we can walk on" - and made it dangerous.

Second: you've not just taken the ground away. You've replaced it with something else (again metaphorically, and incidentally also literally). The goo follows rules - people just don't know those rules yet. By coming to understand those rules people can come to rely on the goo. We can imagine a future where the goo is just another part of the world that's mostly only dangerous if you don't take the right precautions, like fire or the ocean is in the real world.

Those are the features that I'd try to replicate in order to replicate your first apocalypse's success.

So, what are some features of the world that we rely on right now?

• If you go to sleep, you will naturally wake up in about 8 hours or less. Waking someone up before they wake up naturally is completely safe. Most people don't sleepwalk.
• When a door, chest, bag, etc. is opened, the opening leads to the same place as it did when it was closed.
• You can be confident that you are the original you, not a copy that thinks that it's the original.
• Spellcasting is difficult enough that there's no risk that ordinary speech, movements, etc. will accidentally complete the verbal or somatic components of a spell.
• Your memories of life up until this point are memories of a life that you actually lived, not a dream which you just woke up from. You don't need to worry that you'll wake up and find that your current life is just a dream, either. Even if you don't know that you're dreaming when you're dreaming, you know that you're awake when you're awake.
• Natural healing is just free hitpoints. There's no risk or longterm consequences to natural healing.
• Most humans have the same dietary requirements as other humans. Whatever your dietary requirements are, they'll stay similar for your entire life.

I could go on, but you probably don't want a ton of ideas - you just want a few good ones.

I'll elaborate on one possible new set of rules that could replace the first of these points. Perhaps when people sleep, their soul no longer migrates to their own dreamscape - instead, it goes to a shared dreamscape that's a twisted version of the material plane with extra monsters, dangers, bizarre weather, etc. A person awakes when they find a portal out of this dreamscape - but the portals move constantly and may require a short journey to reach.

Waking a person prematurely awakens their body but does not return their soul. An awoken soulless body will be docile, complacent, and incapable of reason but will otherwise retain a person's skills and knowledge. (If you want to keep secrets, you need trusted people to watch you when you sleep!) An awoken soulless body will return to sleep if it is able to do so.

Equipment carries over into the dreamscape from reality, but the version in the dreamscape is a copy. Hit points and spell slots carry over in either direction. Characters gain the benefit of a long rest when they awaken - so, whatever resources they have at the end of the day are all they have in order to escape the dreamscape. Sleeping with a pile of powerful consumable items is a popular tactic for those who wish to adventure in the dreamscape.

Dying in the dreamscape kills people in real life. A person's real body will eventually starve if they stay in the dreamscape for too long. The hazards of the dreamscape are too much for many ordinary people to survive; human populations have been reduced severely since the world was cut off from out natural dreams.

Challenges that this presents to the players include:

• Just surviving! I'll assume that you have a realistic houserule that prevents people from just never sleeping. People in general, and adventurers especially, need to long rest from time to time.
• While in the dreamscape, helping others to escape.
• Scouting out locations in reality by exploring their dreamscape counterparts, which in some cases are actually less dangerous due to being unguarded.
• Precautions must be taken when sleeping out of settlements to protect one's body in the case of an unplanned extended stay in the dreamscape.
• Rescue expeditions into the dreamscape for people who have slept unexpectedly long.
• Exploring the dreamscape to locate portals.
• Clearing out safe zones in the dreamscape.
• Perhaps seeking to extract loot from the dreamscape - if some magic items in the dreamscape can be taken back out and into reality (which IMO should be very weird homebrew items as loot from special places should be special.)

[Bohandas]

One day everyone on the planet suddenly and unexpectedly teleported to a random new location (due to some magical accident or cosmological event or some other hocus pocus). This has caused a collapse of civil order as nobody is where they need to be to do whatever it is they do in society, and because a great many people died due to being teleported to inhospitable locations (ie. deserts, tundras, open ocean, etc) or separated from caretakers (ie. in the case of infants, the very sick, the very old, etc). Optionally some very magically powerful locations with anti-teleport wards in place may have been unaffected, even more optionally the process of protecting these places may mave pushed these wards past their breaking point, either dispelling them or else corrupting them (ex. causing them imprison people inside the warded area by teleporting them back if they try to leave, or scrambling outgoing teleportation, or diverting unrelated teleportation into the warded area, or simply leaving the wards unable to be controlled or lowered by the people who once controlled them). Another optional complication is the possibility that all teleportation magic may have been rendered unreliable and dangerous by the event (effects that didn't have a mishap table before now have one, effects that did have one now have a worse one, or may even just always go to a random location)

EDIT:
Here's another idea. How about some sort of supernaturally enthralling celebration like in that one Powerpuff Girls episode, possibly crossed with the combination cocktail party/raiding party from Life The Universe And Everything.

EDIT:
Another possibility is an implausibly fast breeding pest, in the vein of The Trouble With Tribbles or the mutant rabbits from Night of the Lepus

[Aniikinis]

Everyone in the setting gets the same dream of a single static face that seems just distorted enough for no one to quite make out the features along with the single word of "prepare" with no other clues or hints but the dream never repeats. Exactly 30 days from this dream the sun rises as red as blood with arcs of fire striking the land, shadows are not banished by the light, water turns to blood and begins to boil, and the stars fall from the heavens as meteors. This lasts for three days exactly then everything returns to normal, save for the destruction wrought by the event.

[Bohandas]

"The earth is going to shake violently and deep cracks will open up everywhere and from within will arise big firestorms and screaming demons, but in 48 hours the surface of earth will become unbearable due to extreme heat. All becomes one when the sun comes to earth"
-Check it Out, S4E5

[MetroAlien]

due to a curse, every sapient creature falls asleep at hour X.
All sleepers share the same dream: they're trapped in a maze while an unseen horror hunts them.
Whoever finds the exit, wakes up.
However if the monster catches you...

Sleepers can see and interact with each other in the dream, like it's an MMORPG.
Trying to wake people up doesn't seem to work.
More creative/drastic attempts at wake-uppery end poorly for all involved.

This scenario has a few notable features:

since everyone is forced to sleep at a specified time, there's no such thing as a night watch.
Whoever escapes the maze early gets to catch the worm, so to speak.
Everyone has to make safety precautions before sleeping time comes, especially if you're out in the wild, since animals aren't affected.

While the players can hunt for the culprit/source in the waking world, they can't effectively use weapons etc. to fight the monster.

While the dreamy threat can't be faced with regular weapons/magic, it can still be designed as a skill-based encounter. It just requires some creativity from both the DM and players (and setting up rules for the dream world)