Walking a full day, all day and Fatigue rules

[Red Rubber Band]

A campaign setting I am creating has a world where there is 6 months of darkness followed by 6 months of light. The darkness contains all manner of horrible things, hordes of demons, and to survive you need an incredibly resilient stronghold. The other option for any inhabitant of this land is to stay ahead of the darkness by constantly moving.

How far per day (say 16 hours, 8 hours for rest as I'm not completely without heart) would it be reasonable for PCs to travel? Remember that this is constant travelling. You dawdle one day and the darkness will catch up, forcing you to exhaust yourself the next day to outrun the horrors behind you.

I understand that travelling spells will throw a hamper into this, but that's an issue for another day.

Average human walking speed is ~5km/hour, 16 hours of this gives you 80kms/day, and in a year of 365 days that is nearly 30,000kms. Is that ok to leave as is? Assume this world is smaller than Earth (which has a circumference of a shade over 40,000km) and the line that people walk is, for the most part, unbroken.

I am not really up on the fatigue and exhaustion rules, so am not sure how badly they impact this.

[DungeonMaster11]

Well is the terrain all flat? Because difficult terrain such as up hill or through jungles will slow the party down, but if it is all flat, then that sounds reasonable.

[nyjastul69]

The rules for overland movement can be found here (http://www.d20srd.org/srd/movement.htm#overlandMovement).

[Karl Aegis]

Back in the day, it took boats three years to circumnavigate the planet. By ground it can take 3-5 years and by air it can be done faster than a week. Around the World in Eighty Days was a movie with Jackie Chan, if I recall correctly.

[Red Rubber Band]

Well is the terrain all flat? Because difficult terrain such as up hill or through jungles will slow the party down, but if it is all flat, then that sounds reasonable.

It will be largely flat and easy to walk. Centuries of people making the journey will have worn paths through vegetation. Of course I will throw several obstacles in their way, just trying to get an average speed sorted out for generic, featureless plains to start with.

[marphod]

I am not really up on the fatigue and exhaustion rules, so am not sure how badly they impact this.

You're looking for the Forced March (http://www.d20srd.org/srd/movement.htm) rules. Specifically:

A character can walk 8 hours in a day of travel without a problem. Walking for longer than that can wear him or her out
For each hour beyond 8, each character has to make a Con check (DC10 +2/extra hour); failure means the character takes non-lethal damage and becomes fatigued.

If you have access to lots of healing magic, this isn't terribly significant, as healing the damage removes the fatigue, but even so, more than 8 hours of march is pushing feasibility. PCs still need to make and break camp, eat, take 'natural' breaks, study spellbooks or meditate, and they (or someone) will need time for Crafting. RAW, creatures with land movement of 30' can cover 24 miles (38.6km) a day on easy ground. Less on rough roads or trailblazing.

Given appropriate mounts, and travelling lightly, you can push this up to 48 miles (77.2km) per day, but even the best horse is going to fail after doing that day over day.

On the other hand, they only need to cover that distance if they are at the equator; if they are at 60deg north or south of the equator, they only need to travel half the planet's circumference per year. At 45deg, its around 75% ((Sqrt2)/2).


If they all have rings of sustenance, none need more than an hour to prepare spells, and such, feel free to make them run as far as you like. For the more mortal ones, cut your circumference in half, or put them well off the equator.

[Telonius]

Back in the day, it took boats three years to circumnavigate the planet. By ground it can take 3-5 years and by air it can be done faster than a week. Around the World in Eighty Days was a movie with Jackie Chan, if I recall correctly.

The original book was by Jules Verne.

::shuffles away, muttering things about kids today and getting off the lawn::

[marphod]

::shuffles away, muttering things about kids today and getting off the lawn::

Then there was the article on Johnny Cash's career I saw a couple of months back that had a line about Trent Reznor/Nine Inch Nail covering Johnny Cash's Hurt.

[ShaneMRoth]

Assuming that walking is the only reliable transportation method...

A Barbarian with the Endurance Feat (+4 for forced march Con checks) and an 18 Constitution (+4 for all Con checks) would be the most likely candidate to survive, and it would be touch and go the entire time.

Everyone else would be swallowed by the darkness unless they were very, very lucky.

Base Speed of 40. Assume he travels light, as wearing heavy armor or anything else that slows a person down in this scenario is life-threatening.

The Barbarian can make the 80 km (48 mile... I use miles) distance in 12 hours. He will need to make four Constitution checks.

If the DM is feeling generous and allowing a Take 10 (which would likely be a house rule, as a CON check isn't clearly described in the Core Rules as a Skill) then the Barbarian would be guaranteed to make the 4 checks necessary.

Hour Nine: DC 10
Hour Ten: DC 12
Hour Eleven: DC 14
Hour Twelve: DC 16

Even this fleet footed Cardiovascular Conan will not be able to reliably travel much longer on a daily basis.

Hour Thirteen: DC 18
Hour Fourteen: DC 20
Hour Fifteen: DC 22
Hour Sixteen: DC 24.

If the DM required actual rolls every day, then there would be some days when he failed to make the full 80 km...

Also, it would be a survival strategy to leave campsites in tact for others to use. Every 80 klicks there could feasibly be enough of a campsite to where no one really had to start from scratch. Particularly with six months lead time.

There would be no point in waiting the six months to start walking. The best survival strategy would be to follow the darkness, not be chased by it. Staying as close to the trailing border of the darkness as you could.

Characters would have to be able to average 80 clicks a day over six months. Otherwise, they will not be able to outrun the darkness.

Strategies that allowed people to get rest on the move would be tempting.

If the path were a waterway, like a canal, then a boat could be kept moving at all times, and people could sleep in shifts.

Magic items that facilitated movement and increased CON scores would be life-saving.

Low level spells like Longstrider and Mount would be popular load-outs. Cure light wounds is always a popular load out.

The Phantom Steed spell is the lowest level spell I can find which, cast repeatedly, could reliably allow characters to stay ahead of the darkness.

Overland Flight is the lowest level spell I can find which, cast once, could reliably allow this.

[Troacctid]

Best strategy is to teleport, as usual.

[Flickerdart]

Assume that the people who can do magic can magic themselves out of this.

Now look at everyone else. The people? Forget the people. Think about the things they eat.

Flora? With only 6 months to recover from demon-related scouring, nothing will grow naturally. Fauna? Same deal - your average fish or deer or whatever has a very limited ability to not get scourged. Nobody driving herds is going to be able to keep up with the pace they need (and the herds can't graze anyway because everything was ruined). Stronghold dwellers can at least plant some kind of crop and then quickly harvest it before horrible death, but your nomads are pretty much screwed unless they can live off air and rocks.

Pretty much the only kind of animal life that's going to survive in this kind of thing is migratory birds, who are able to move fast enough to keep ahead of the demons, and can raid strongholder farms without being too put upon by things like fences that would keep out larger creatures. In order to sustain every nomad, you're gonna need a lot of birds. And maybe raptoran nomads that have herds of these birds. With little flying sheepdogs.

[Bucky]

If the DM required actual rolls every day, then there would be some days when he failed to make the full 80 km...

The penalty for failing a roll is 1d6 nonlethal damage, but speed penalties don't kick in until exhaustion after two failed Con checks. And our barbarian has the HP to keep going until exhaustion.

For those with more hit dice but bad rolls, they can walk 10 hours to exhaustion, alternate between 1 hour rest and one hour walking three times, and sleep 8 hours for a total of 13 hours' travel per day and 5d6 (avg. 18, max 30) nonlethal damage. They can also hustle for the first hour of each day without penalty, for a 14th hours' distance.

[Necroticplague]

If you have fast healing or regeneration, keeping up a forced march forever is fairly trivial. And technically, there aren't any raw penalties for sleep deprivation. So I suspect natural selection would make Feral humanoids incredibly common, especially considering the template also increases their speed (so not only can they keep on walking more, but they do it faster too).

[ksbsnowowl]

The breakdowns above are good. Basically, commoners will have to stay in the higher latitudes so they can do 'great circle routes' of a sort. Anything near the equator would kill them, unless this is a much smaller world than earth.

Your typical 1st level Commoner will collapse into unconsciousness after 10 hours of walking. That would be 30 miles for an adult (not outlandish to assume smaller children have a 20 foot walking speed, but let's ignore that for the moment).

A quick search shows me the circumference of the earth is 24,901 miles. Divide that by 30, and it would take a touch over 830 days for the average 1st level Commoner to walk that distance.

To be able to make the trek within a 365 day year, the commoners would have to stay north or south of 64 degrees latitude. (10,945 mile circumference; 30*365 = 10,950). For reference, 60* North Latitude is the southern coast of Finland, and Oslo, Norway. While 64* North is just a smidge south of Reykjavik, Iceland.

Factor in weather, and a commoner has no chance to even reach adulthood. Unless the planet is closer to its sun, in which case the equator would be inhospitable to humans, and you would have divergent humanoid populations near the poles.

Alternatively, your world would need to be 44% the size of our earth, by circumference (that's 8.5% the size of our earth by volume), if you want commoners able to survive at the equator. Assuming you want gravity to work by the same laws of physics that apply to us... well, the gravity will be more than what it is on our Moon, but not much.

Mercury is the closest planet in size to what I described above.

[Flickerdart]

A quick search shows me the circumference of the earth is 24,901 miles. Divide that by 30, and it would take a touch over 830 days for the average 1st level Commoner to walk that distance.

To be able to make the trek within a 365 day year...
Why does a year need to be 365 days? Instead of making the planet smaller, it could just orbit more slowly.

[Telonius]

Why does a year need to be 365 days? Instead of making the planet smaller, it could just orbit more slowly.

You know, I'm not sure they ever specifically defined a "year," even though they do base a bunch of rules off off it (age categories, some spell durations, replacing a familiar, Arcane Archer's Arrow of Death duration...)

[Bucky]

Factor in weather, and a commoner has no chance to even reach adulthood. Unless the planet is closer to its sun, in which case the equator would be inhospitable to humans, and you would have divergent humanoid populations near the poles.

The planet might not be closer to the sun, but the arctic wanderers do at least get the benefits of an eternal summer.


Why does a year need to be 365 days? Instead of making the planet smaller, it could just orbit more slowly.

The length of a year is less relevant than the length of a planetary day. If the planet's rotating just slightly faster than once per solar orbit, it could orbit once per year but have 'days' that last centuries.

[SangoProduction]

The breakdowns above are good. Basically, commoners will have to stay in the higher latitudes so they can do 'great circle routes' of a sort. Anything near the equator would kill them, unless this is a much smaller world than earth.

Your typical 1st level Commoner will collapse into unconsciousness after 10 hours of walking. That would be 30 miles for an adult (not outlandish to assume smaller children have a 20 foot walking speed, but let's ignore that for the moment).

A quick search shows me the circumference of the earth is 24,901 miles. Divide that by 30, and it would take a touch over 830 days for the average 1st level Commoner to walk that distance.

To be able to make the trek within a 365 day year, the commoners would have to stay north or south of 64 degrees latitude. (10,945 mile circumference; 30*365 = 10,950). For reference, 60* North Latitude is the southern coast of Finland, and Oslo, Norway. While 64* North is just a smidge south of Reykjavik, Iceland.

Factor in weather, and a commoner has no chance to even reach adulthood. Unless the planet is closer to its sun, in which case the equator would be inhospitable to humans, and you would have divergent humanoid populations near the poles.

Alternatively, your world would need to be 44% the size of our earth, by circumference (that's 8.5% the size of our earth by volume), if you want commoners able to survive at the equator. Assuming you want gravity to work by the same laws of physics that apply to us... well, the gravity will be more than what it is on our Moon, but not much.

Mercury is the closest planet in size to what I described above.

Surviving to adulthood? Dude, you think there are even children being born on this type of world? lol. Once you've become stricken with pregnancy, you're basically dead. And strenuous exercise every day, all day, along with the stress of demons, even if the female somehow survived, she'd have killed her unborn child.

And so, actually, the only people who will be around in a few years... decades, if others are lucky... after this starts, are the experienced mages....and those heavily blessed by their gods...because that's the only way they are getting food as well. Yeah...lol. Survival of the fittest =/= mean the fittest people actually survive, lol.

Also, something slightly less pressing, in a world of magic, with such a small mass of the planet, it would have a significantly thinner atmosphere. So, guess running's out of the question lol. Back to magic then, with their air bubbles and what not.

However...with a reduced mass of the planet comes reduced reduced weight of the travelers....but that also means muscle decay, even if you came from another world. If you were born on this world, well, you're just outa luck, as you have no special advantage for a low gravity world (outside of perhaps being physiologically adapted for it, and like...not having your eyes explode).

[And yes, I realize the bit about being able to get a longer year by the planet being further away, i just jump off from what this comment said. Also, you'd need more protection from cold the further the planet is away, which means you need to be closer to the equator. Someone needs to do the math for where the benefits of being further outweigh the benefits of being smaller (...probably want to start with where you are able to breathe....)]

[Flickerdart]

The length of a year is less relevant than the length of a planetary day. If the planet's rotating just slightly faster than once per solar orbit, it could orbit once per year but have 'days' that last centuries.
The OP specified that the demons are on a calendar, not a clock, so the length of a year is entirely relevant, and the length of the day not at all.

[Bucky]

I would assume that the main purpose of strongholds is to protect pregnant women and small children.

[SangoProduction]

Thought of a new problem, specifically with the strongholds (other than somehow surviving against 6 months of demons)...it's the darkness. Humans kinda need the sun to make vital nutrients. But, there's no rules for this, so I guess it can be ignored. Same with sun burn. ~14 hours of walking/hustling would give untold amounts of exposure to the sun.
(I'm assuming the demons basically tear up anything they come across, so no trees or above-ground shelters to protect from the sun.)

[PaucaTerrorem]

Then there was the article on Johnny Cash's career I saw a couple of months back that had a line about Trent Reznor/Nine Inch Nail covering Johnny Cash's Hurt.

That's it. Rage quit.

[Chronikoce]

Surviving to adulthood? Dude, you think there are even children being born on this type of world? lol. Once you've become stricken with pregnancy, you're basically dead. And strenuous exercise every day, all day, along with the stress of demons, even if the female somehow survived, she'd have killed her unborn child.

And so, actually, the only people who will be around in a few years... decades, if others are lucky... after this starts, are the experienced mages....and those heavily blessed by their gods...because that's the only way they are getting food as well. Yeah...lol. Survival of the fittest =/= mean the fittest people actually survive, lol.

Also, something slightly less pressing, in a world of magic, with such a small mass of the planet, it would have a significantly thinner atmosphere. So, guess running's out of the question lol. Back to magic then, with their air bubbles and what not.

However...with a reduced mass of the planet comes reduced reduced weight of the travelers....but that also means muscle decay, even if you came from another world. If you were born on this world, well, you're just outa luck, as you have no special advantage for a low gravity world (outside of perhaps being physiologically adapted for it, and like...not having your eyes explode).

[And yes, I realize the bit about being able to get a longer year by the planet being further away, i just jump off from what this comment said. Also, you'd need more protection from cold the further the planet is away, which means you need to be closer to the equator. Someone needs to do the math for where the benefits of being further outweigh the benefits of being smaller (...probably want to start with where you are able to breathe....)]

You underestimate the physical activity that women can sustain while pregnant. Someone who is already in peak physical condition and maintains that activity would not be putting sudden and undue strain on their body. The human body is massively adaptive and could cope. Especially if as another poster mentioned they were chasing the night side rather than fleeing from it. This would allow them to lose days when they are feeling more worn out and gain days when they feel better.

Food is a legitimate concern since feeding yourself does become a hardship. This could be overcome as another poster mentioned if the main source of meat is from migratory birds that stay ahead of the darkness and the main source of plant life is from stronghold production. The most defensible strongholds are likely built using natural surroundings such as mountains so I image a diet that uses lots of fungi that grow in dark, wet environments would be cultivated. Those who are runners could trade services in exchange for food. Transport in long distances in the direction of the darkness movement is a possible employment ability. If you set up a network of major strongholds around the world and had them hire runners to deliver goods they could keep each other supplied by providing any necessities not available in other areas.

Your other concerns do not really make sense in my opinion. Their bodies would have evolved to appropriately survive under the conditions of their world. Gravity and oxygen levels would not seem strange to them, rather they would be completely normal.




Thought of a new problem, specifically with the strongholds (other than somehow surviving against 6 months of demons)...it's the darkness. Humans kinda need the sun to make vital nutrients. But, there's no rules for this, so I guess it can be ignored. Same with sun burn. ~14 hours of walking/hustling would give untold amounts of exposure to the sun.
(I'm assuming the demons basically tear up anything they come across, so no trees or above-ground shelters to protect from the sun.)

Humans already live in climates on this world where the day-night cycle is extreme. Ny-Ålesund Norway has a permanent population of 35 and experiences a "night" that lasts on average 115 days. Granted it is not pitch black and they experience faint light and twilight around midday. It is still possible for humans to live under these conditions. Similarly they experience a daylight period where the sun does not set for on average 128 days.

[Keltest]

Frankly, it seems to me that the OP needs to throw humanity a bone in his setting or theyre going to go extinct. Unless the strongholds are capable of protecting massive populations and produce enough food to be self-sufficient, even theyre going to have some seriously hard times. The Nomads are going to die, period, unless theyre groups of mid-high level barbarians or other classes with enough physical ability to outrun their impending deaths.

I think the idea of just making the darkness move slower has potential, though the strongholds are still going to need some very careful planning and research.

Out of curiosity, what happens underground? Could the strongholds work like dwarven cities, farming underground food like Mushrooms and the like? Or would that just be another door for the demons to get in through?

[Jack_Simth]

Low level spells like Longstrider and Mount would be popular load-outs. Cure light wounds is always a popular load out.

The Phantom Steed spell is the lowest level spell I can find which, cast repeatedly, could reliably allow characters to stay ahead of the darkness.

Overland Flight is the lowest level spell I can find which, cast once, could reliably allow this.
If you're looking at a required 48 miles a day on average (a human walking 16 hours per day)? You want Animate Dead.

No, seriously. Horse and cart. Sleep in shifts while riding. Kill the horse, animate it as a skeleton, have it draw the wagon. 2 miles per hour... but undead are immune to nonlethal and fatigue. Thus, the wagon can go 24 hours a day. That's 48 miles. The people in the wagon? Only one needs to be awake. And if you have a method of healing the undead horse, of course, you can even have it Hustle periodically.

As to plants:
There's a lot of plants that have a life cycle compatible with only six months until destruction. As long as the seeds can survive the demons (and quite frankly, seeds can be ridiculously plentiful and durable), there would be plants. Lots of them. They just wouldn't be the stuff we're used to.

[marphod]

Surviving to adulthood? Dude, you think there are even children being born on this type of world? lol. Once you've become stricken with pregnancy, you're basically dead. And strenuous exercise every day, all day, along with the stress of demons, even if the female somehow survived, she'd have killed her unborn child.

Anthropological evidence disagrees with that. Early humans were nomadic plains-runners, and while pregnant mothers were not necessarily going to keep up with most of the hunters during their sprints, they did keep up with the tribe. Motherhood was also a lot more frequently fatal, but tribes still averaged long-term population growth.

[HurinTheCursed]

Remember the group moves at the slowest speed among its members, unequiped, a single dwarf or halfling would cut the speed of the whole group.
Horses, organized in relay can speed up a group. If there is no relay, at least 2 per character would allow mounts to take subdual damage rather than lethal damage.
Then spells like remove fatigue, mass longstrider, feathers, wind walk, teleport will help.
Ring of sustenance and easy travel armors may become a must buy !
Even endurance would become useful in such a challenge.

If they take night shift and never use survival for food, you can add 2 hours sleep for a 4-adventurer group unless elves are present. The group training called group transe (iirc) can shorten this but makes night encounters more problematic.
Some need 1h to pray or to prepare spells, some need to teach trick to their companions, some want to craft small stuff...

Another way would be to use some vehicle, probably waterborne. Those move 24/24 without fatigue and only require shift.

[SangoProduction]

Anthropological evidence disagrees with that. Early humans were nomadic plains-runners, and while pregnant mothers were not necessarily going to keep up with most of the hunters during their sprints, they did keep up with the tribe. Motherhood was also a lot more frequently fatal, but tribes still averaged long-term population growth.

But nomads never were forced to run or they die. Nor did they have to run around 14-16 hours a day. But, this is a world that is far beyond human capabilities (excluding machines)...well, some of them are...and they are often called heroes. Perhaps it would work though. Perhaps it's feasible that if this thing went on for enough generations, I'd say all nomad-born would get an implicit +4 vs saves against fatigue.

[SangoProduction]

Another way would be to use some vehicle, probably waterborne. Those move 24/24 without fatigue and only require shift.

Waterborne transportation is a no-no, unless any wreckage is cleared when the demons come by...or the stream's completely flat all the way around the world. And, while in theory, if it was, it would be faster because of 24/7 travel (it would certainly be easier on the nomads at least), most rivers that aren't freshly made (geologically speaking) have curves in them.

Of course, the spell Dig could get rid of them, but if we are bringing magic, why not just say teleport or like someone else suggested, raise dead.

[Necroticplague]

Another alternative: there could be groups where the Shadow template is common. This template makes you impossible to see in the dark, makes you a good deal faster (50% speed increase), and can grant fast healing. Seems like it's be a perfect fit for this place.

[Spore]

As i think he have now checked our astrophysics homework that this planet is largely not habitable (6 months of darkness and demon scouring followed by possibly 6 months or sunshine and drought, the planet not being in the habitable zone near a star, and the rotation killing the inhabiting hiking people) let's just assume "a wizard did it" and leave it at that. The darkness could transform normal organisms into dire creatures, demons and plants of darkness (fungi, plant monsters and similar).

I would say that there is a zone near the equator where strongholds are the only proper possibility to survive (maybe some kind of Underdark where "darkness light" resides continually). Closer to the poles there is more wandering going on (and there is actually a reason to settle in semiarctic lands other than silence from pesky mobs).

[SangoProduction]

(I'm assuming migratory birds are similar to real ones....because there's no RAW information on them. But, in a mythical land, migratory birds bred and raised to outrun this dark could be possible.)
There is a bird that can make non-stop flights of over 10,000 kilometers to breed, called the Shorebird. It can also fly over 60 mph. Also, they can gain up to 1/2 their weight in fat before the migration. Not a bad candidate, if I say so myself.

If we agree that the equator's length is around 15k - 20k kilometers all around, then this bird could probably make it. However, they will lose a lot of their fat at the end of the journey though, so ideally, quite a few would be slaughtered at some set rest points. Perhaps between strong holds of roughly 3 to 5k kilometers apart. But, since the only food source that could feed these things is in the strong holds...well, it's essentially like having a battery of food...if that battery was exceptionally leak-prone. It won't really do you an incredible amount of good to have these things, as it's not "generating" or "gathering" food, so much as storing it....poorly.

UNLESS! This fungus that the strongholds live off of take time to grow after the light . EDIT: nope. Forget that. In order for that to work, the caravans would have to go backwards, into the places that have been consumed by the darkness, which will probably result in the birds getting killed.
Wait, I thought of something else! What if some strongholds are placed less for sustainability, and more to have a place where nomads could go if something bad happened. (Of course, they'd still need the same defensive capabilities of other ones, but perhaps their terrain isn't as good for the farming of fungus?) Or maybe all of the land in the stronghold is devoted to mining resources. In this case, caravans would go to these places to restock them, in exchange for other goods, which would be passed on to the next stronghold.

But, there's something better than birds for this purpose! Insects. That's right, insects. Where as the shorebird can have up to 33% of its weight be fat (and some other percentage be the least-bit calorie rich), the entire insect can be eaten, such as in the case of grasshoppers. Also, you won't be burning through their calories by making them move, as you can just cage them up and take them with you, preferably by some sorta mass-transportation device or caravan.
Again, these are basically batteries more than anything, and still don't do you much good, but for what they are doing, they'll work.

However, I think there may be a way to actually generate food using animals, although it requires magic. Use an appropriately sized Ring of Sustenance on the largest animals you can sustain/keep in the strongholds. I would recommend a bear, as they can grow pretty massive in terms of pure fat when it's time for them to hibernate. Selectively breed for the longest-hibernating bears, or magically create them, since you're already using magic, and boom shaka locka, feasts for everyone at the cost of 1 ring of sustenance.

Of course, rings of sustenance are going to be expensive as hell in this world, because of the raw necessity of them...perhaps some of the strongholds are also like mana nodes, and allow the creation of massive amounts of items, which are necessary for other forts? (Still at inflated prices, because more people than just adventurers will be demanding them, but still.)

Also, the inflated prices makes magic item efficiency all the more necessary, so the bear idea is actually quite useful.

[Red Rubber Band]

Thanks for the replies, everyone! Keep the comments coming.

I'm trying to find a good medium for the speed of darkness at the moment. 80kms a day was a number I picked from the air.
Assuming a walking speed of 5kms/hour in a 16 hour day, they'd keep pace with the darkness. Of course we're not in a perfect world so things will go wrong.

What about halving it to 40kms? This will allow for a slower pace, things going wrong, the ability to catch up.

Adaptation and change are trademark traits of humans - even nature over a long enough period of time - and I feel that some of you are being a tad over the top. Not everyone is going to die. And if the world was always like this then things will have evolved to deal with it.

Plants that are safe for humanoids to eat, but deadly to devils/demons/whatever I put in the dark. Animals that have evolved to meet the requirements of this world either by hibernating for 6 months of a year (burrowing into trees/the ground) or are made to withstand the constant marathon of life. Horses pulling wagons that contain a bed of soil, used to grow smaller crops. Herds of cattle, if they exist, will be small and require incredible skill to manage. There would even be those that stalk through the night, daredevils that bring news and items of aid between strongholds.

[SangoProduction]

Thanks for the replies, everyone! Keep the comments coming.

I'm trying to find a good medium for the speed of darkness at the moment. 80kms a day was a number I picked from the air.
Assuming a walking speed of 5kms/hour in a 16 hour day, they'd keep pace with the darkness. Of course we're not in a perfect world so things will go wrong.

What about halving it to 40kms? This will allow for a slower pace, things going wrong, the ability to catch up.

Adaptation and change are trademark traits of humans - even nature over a long enough period of time - and I feel that some of you are being a tad over the top. Not everyone is going to die. And if the world was always like this then things will have evolved to deal with it.

Plants that are safe for humanoids to eat, but deadly to devils/demons/whatever I put in the dark. Animals that have evolved to meet the requirements of this world either by hibernating for 6 months of a year (burrowing into trees/the ground) or are made to withstand the constant marathon of life. Horses pulling wagons that contain a bed of soil, used to grow smaller crops. Herds of cattle, if they exist, will be small and require incredible skill to manage. There would even be those that stalk through the night, daredevils that bring news and items of aid between strongholds.

Over the top? We were comparing demons to average humans, and animals. We imagined the demons to be on a pure destruction bent, and destroys everything they come across, including the plants. In order for evolution to work, some of them have to already be that way before the extinction (demon) comes. It could be possible in a world of magic, but definitely not standard, and thus wouldn't have existed in the first place.

Unless the demons use a sort of radiation, which forces the sudden change, and often terrible death, of organisms? That doesn't work for strongholds though, unless they are lead-lined. Anyway, quite overthinking it, as if the GM says there are, there are. And, what's that saying? Every time someone brings science into D&D Palor kills a cat girl, right?

But sometimes it's fun to overthink things.

[Elkad]

Another spot where RAW underestimates capabilities.

Roman soldier standard (for day after day) was 20 miles in 5 hours. Followed by building fortifications, maintaining equipment, standing guard several hours a night, destroying the fort, and doing it again. Forced march days bumped the distance by 20% (in the same 5 hours)

People do 30 miles a day for 100 days straight hiking the Pacific Crest Trail, which isn't exactly walking down a road.

On a flat plain, in a society where everyone has walked every day since birth? Those people should probably get a racial trait of +10 movement speed (ala barbarian), and probably a custom feat similar to Run, but instead of a runspeed bonus, you get to march an extra 2 hours a day.

6 hours of walking, plus 2 hours of hustle (dealing 1pt of non-lethal, fixed by resting for the night) gives you 40 miles a day. They still fall behind at the equator. At the 45th parallel, they actually gain about 4 miles a day (or can only hustle for a single hour, skipping the point of damage). Given a feat for an extra 2 hours of movement, it becomes 48 miles.

The fitter people (able to travel faster) can dip closer to the equator. Foraging will probably be better (less traffic), but you have to cover more ground every day. As you slow down, you shift away from the equator so you don't need to cover as much distance. But the weather gets poor and competition for resources increases.

If it gets cold in the months of darkness, the trailing (spring) edge may have snow or ice covering it. And food may be scarce for weeks. So chasing the dark again slows you down, forcing you back towards the center.

Dang, I really like this. I'm already picturing the oddity of journeying to a distant kingdom which is moving, the priest-run patrols that stay a week in front of the dark with wagons collecting the infirm (holding lotteries if the wagons are full?), the difficulty of traveling any direction except West, etc.

You'd march next to the same people for months at a time, occasionally passing the weak or being passed by the strong. If you stopped for even a few days, it might take you months to catch back up with your clan. You would cook meals, conduct business, courtships, and everything else at a walk. Anyone with actual fast movement (including our heroes) who would have knowledge of areas far to the North/South would be a wonder like any traveler from a distant land would be on a normal world.

And in a meta sense, it sure puts a big damper on the 15-minute adventuring day. The players have to keep moving towards the next encounter.

[Red Rubber Band]

Over the top? We were comparing demons to average humans, and animals. We imagined the demons to be on a pure destruction bent, and destroys everything they come across, including the plants. In order for evolution to work, some of them have to already be that way before the extinction (demon) comes. It could be possible in a world of magic, but definitely not standard, and thus wouldn't have existed in the first place.

Unless the demons use a sort of radiation, which forces the sudden change, and often terrible death, of organisms? That doesn't work for strongholds though, unless they are lead-lined. Anyway, quite overthinking it, as if the GM says there are, there are. And, what's that saying? Every time someone brings science into D&D Palor kills a cat girl, right?
You forget that these won't be "average" humans, even if I did start it off by using average, our world walking speeds. These people will be bred for this type of life. And, as has been pointed out a few times, people are a lot hardier than they are being given credit for.
I never said the demons were destroying everything they came across, let alone stripping the landscape bare of plants.
As for it not existing in the first place, I'm not doing an origin story so I'll leave that to the comic book writers or theoretical physicists :smalltongue:


Another spot where RAW underestimates capabilities.

Roman soldier standard (for day after day) was 20 miles in 5 hours. Followed by building fortifications, maintaining equipment, standing guard several hours a night, destroying the fort, and doing it again. Forced march days bumped the distance by 20% (in the same 5 hours)

People do 30 miles a day for 100 days straight hiking the Pacific Crest Trail, which isn't exactly walking down a road.

On a flat plain, in a society where everyone has walked every day since birth? Those people should probably get a racial trait of +10 movement speed (ala barbarian), and probably a custom feat similar to Run, but instead of a runspeed bonus, you get to march an extra 2 hours a day.

6 hours of walking, plus 2 hours of hustle (dealing 1pt of non-lethal, fixed by resting for the night) gives you 40 miles a day. They still fall behind at the equator. At the 45th parallel, they actually gain about 4 miles a day (or can only hustle for a single hour, skipping the point of damage). Given a feat for an extra 2 hours of movement, it becomes 48 miles.

The fitter people (able to travel faster) can dip closer to the equator. Foraging will probably be better (less traffic), but you have to cover more ground every day. As you slow down, you shift away from the equator so you don't need to cover as much distance. But the weather gets poor and competition for resources increases.

If it gets cold in the months of darkness, the trailing (spring) edge may have snow or ice covering it. And food may be scarce for weeks. So chasing the dark again slows you down, forcing you back towards the center.

Dang, I really like this. I'm already picturing the oddity of journeying to a distant kingdom which is moving, the priest-run patrols that stay a week in front of the dark with wagons collecting the infirm (holding lotteries if the wagons are full?), the difficulty of traveling any direction except West, etc.

You'd march next to the same people for months at a time, occasionally passing the weak or being passed by the strong. If you stopped for even a few days, it might take you months to catch back up with your clan. You would cook meals, conduct business, courtships, and everything else at a walk. Anyone with actual fast movement (including our heroes) who would have knowledge of areas far to the North/South would be a wonder like any traveler from a distant land would be on a normal world.

And in a meta sense, it sure puts a big damper on the 15-minute adventuring day. The players have to keep moving towards the next encounter.
I like your ideas. I was thinking more along the lines of a "nobility" path, a nice set of terrain that gives you an easy distance to trek, but also not too close to the cold.
All of this stuff is good, and I'm looking forward to running it once our current campaign (and another after that :smallsigh:) ends.

[Story]

If the DM is feeling generous and allowing a Take 10 (which would likely be a house rule, as a CON check isn't clearly described in the Core Rules as a Skill).

You can take 10 on ability checks too, so no houserules are required.


The Phantom Steed spell is the lowest level spell I can find which, cast repeatedly, could reliably allow characters to stay ahead of the darkness.

What about Traveler's Mount?


And technically, there aren't any raw penalties for sleep deprivation.

I've heard that the Elder Evils book includes a section with penalties for sleep deprivation, but that may be related specifically to the Elder Evils.

[daremetoidareyo]

If humans are making this trek, then animals are too. You probably want giant herds of reptiles, and fist sized bugs that have to be dealt with.

You want reptiles because they are exothermic and would be energized by the sun.

People could follow the "migration", which has stomped a path through the rougher terrain.

There would probably be a couple major migration paths. Entire cultures of houses strapped to fat lizard elephants. Strict rules about which parts of the herd can be eaten.

There is a rumor about an underground river lined with moss that generates light that can carry people about a quarter of the distance around the world, where there are plenty of blind fish, sonar bugs, giant waterstriding bats. It's said that The remnants of the gnolls and goblinoids (pick whatever race you want that would be incompatible with the demihumans) use this path.

We need to talk about water. Where and how does it lay: oceans? giant lakes? rivers only? Then we have to figure out how to access water in at least 3 day intervals along the migration route. Without magic, the only option is to invent a new race of creature.

You know how plants give free pollen to bees under the assumption that the bee does all of the hard work of sex for it? Using that as a model, where bee gets free food, plant gets free reproduction efforts, what would happen if something used people to reproduce and they attracted people to themselves by bringing water?

So these flying cuplike plantlike creatures fly on four wings to scoop up water and just follow the migration, but they really just fly anywhere. They generate energy through photosynthesis. They fly to life forms, who kill them, greedily, and eat them directly or ring them out and drink the liquid. In this liquid is the genetic material for the creatures, and inside your creatures bodies, they are likely to find companion genes. They then use animal and demihuman bodies to swap genetic material, become pregnant. People and animals then pass the microscopic creatures out when they evacuate their bowels. This second life stage is where the new crop get back to the major water sources. You have two options that I can think of:
1.) they just sit in the ground and wait for the demons to come around. When the demons come, they inject themselves into their bare feet like hookworms. They then take over the nervous system of the demon and make it run towards the nearest water sources. People sometimes talk about "rogue demons" that just give up the fight and run away at random, sometimes clawing at others of their kind. But only the people in the strongholds and at the edges of darkness have seen it.
Anyway, Meanwhile, the eggs of the cup creatures fill up the demons body, decaying it from the outside, as they absorb nutrients, and when the demon finally reaches the water, The DEMON BURSTS on contact with the water like an explosion: shooting a new generation of flying cuplike creatures to scoop up water and find the herd again.

or

2.) There is a single plant on the entire planet. It is a runner root type plant like bamboo, but it bears fruit. This thing is huge and it's root system extends all the way to underground water sources and the ocean. It is constantly growing in the sun zones, People can actually watch the ground break at walking pace as the roots move and shoot up shoots. These cup creatures that were passed by animals bore into these root networks and follow the natural hydrostatic system of the giant plant towards water.

If people give you too much grief about the size of the planet, remember that the center of this planet could be filled with denser elements than earth's that keep the gravity familiar.

[BioCharge]

Alternatively, instead of just the people moving, there'd be entire moving cities. I don't see why the concept of moving towers (http://archive.wizards.com/default.asp?x=dnd/cw/20070423a) couldn't be extrapolated to small hamlets or villages. Heck, the netherese made flying mountains in the Forgotten Realms setting.

[Jack_Simth]

Heh. Yes, the standard Mount (http://www.d20srd.org/srd/spells/mount.htm) spell provides a Light Horse (http://www.d20srd.org/srd/monsters/horse.htm#horseLight) with bit and bridle for 2 hours/level. Let's see.. 1st level human Sorcerer, 12 Cha (non-elite array), gets 4 1st level spells each day. If said Sorcerer knows Mount, that's 8 hours of riding at a move of 60 (6 mph, a little over 9.5 kph). Hustle the horse for the duration (it'll take a point of lethal damage before the duration runs out... and it's got 19 HP, no big deal), and that's 19 kph for two hours per casting = 38 kilometers per casting. Two castings get 76 kilometers or 48 miles. Which means a Sorcerer with 12 Charisma can take care of himself and his wife.... and only spend 4 hours a day on travel.

[daremetoidareyo]

Yeah, you could always make a decadent subrace of airgnomes in a cloud fortress stocked with unseen servant prostitutes and libraries and taxes that come in the form of blood because the magic engines that keep the fortress afloat runs on magic that must be fueled by pain.

[Elkad]

I like your ideas. I was thinking more along the lines of a "nobility" path, a nice set of terrain that gives you an easy distance to trek, but also not too close to the cold.
All of this stuff is good, and I'm looking forward to running it once our current campaign (and another after that :smallsigh:) ends.


Yup, there will definitely be a sweet zone. Latitude for easy distance vs good weather. Trailing just far enough behind the "spring" edge for foraging to be abundant. Outriders flanking ahead, who keep the rabble from getting ahead of you and taking your forage. If you have the resources to really strip a swath of land as you pass, there would be a dead zone behind you with no food. Competing nobles would try to cut in front of you, taking your forage and forcing you to alter path as well. Possibly right into another group who doesn't want you.

A few really big obstacles to force paths to converge would add nice conflict. Like an old mountain range with a couple easy passes. But you have to get through those with no food, because they are never empty. You'd have a choice of staying on your own latitude line until the last minute, which would make your path longer, but forage better. Or turn early and angle in, but so is everyone else.

The trailing edge is where it really gets interesting (behind my priest-wagons). Full-on disaster mode all the time. Strife and discord would be the rule. A few seconds of killing another traveler for food (or to be food) is far faster than trying to dig edible roots in land that has been trampled for months. Exhausted people staggering along abandoning their possessions, with bands of daring outlaws swooping about. And maybe small raids from the dark (demons under cover of medium-duration darkness spells, etc).

At the dawn edge, you could have caches of wealth hidden and abandoned by people who were falling behind. You could even stash supplies planning for a war next year. Build a cache, fill it with weapons, hide it. When you got back to it next year, you pickup your equipment and raid a neighbor. Of course a lot of these will end up abandoned.

You'd tell where you were in relation to the dark by the position of the sun. If it's late afternoon all the time, you need to pick up the pace.

Imagine a secondary shadowy night. Like an eclipse, it has a variable-appearing path, only last minutes to maybe a couple hours, and comes every few weeks. Just enough time for vampires and other creatures of the dark who have buried themselves for protection from the sun to pop up above-ground and catch several days worth of meals in one frenzy.

[Red Rubber Band]

Lots of interesting stuff, then suddenly:

So these flying cuplike plantlike creatures fly on four wings...
:smallbiggrin: I had to laugh.


Alternatively, instead of just the people moving, there'd be entire moving cities. I don't see why the concept of moving towers (http://archive.wizards.com/default.asp?x=dnd/cw/20070423a) couldn't be extrapolated to small hamlets or villages. Heck, the netherese made flying mountains in the Forgotten Realms setting.
Hmm. I didn't even think of that. Inter-muh-resting.


Heh. Yes, the standard Mount (http://www.d20srd.org/srd/spells/mount.htm) spell provides a Light Horse (http://www.d20srd.org/srd/monsters/horse.htm#horseLight) with bit and bridle for 2 hours/level. Let's see.. 1st level human Sorcerer, 12 Cha (non-elite array), gets 4 1st level spells each day. If said Sorcerer knows Mount, that's 8 hours of riding at a move of 60 (6 mph, a little over 9.5 kph). Hustle the horse for the duration (it'll take a point of lethal damage before the duration runs out... and it's got 19 HP, no big deal), and that's 19 kph for two hours per casting = 38 kilometers per casting. Two castings get 76 kilometers or 48 miles. Which means a Sorcerer with 12 Charisma can take care of himself and his wife.... and only spend 4 hours a day on travel.
Friggin' spellcasters :smallsigh: Looks like low magic campaign, or (preferably) limited access to EzyTravelTM spells.


Yeah, you could always make a decadent subrace of airgnomes in a cloud fortress stocked with unseen servant prostitutes and libraries and taxes that come in the form of blood because the magic engines that keep the fortress afloat runs on magic that must be fueled by pain.
:smalleek: I didn't even notice the gutter until I hit it.


Yup, there will definitely be a sweet zone. Latitude for easy distance vs good weather. Trailing just far enough behind the "spring" edge for foraging to be abundant. Outriders flanking ahead, who keep the rabble from getting ahead of you and taking your forage. If you have the resources to really strip a swath of land as you pass, there would be a dead zone behind you with no food. Competing nobles would try to cut in front of you, taking your forage and forcing you to alter path as well. Possibly right into another group who doesn't want you.

A few really big obstacles to force paths to converge would add nice conflict. Like an old mountain range with a couple easy passes. But you have to get through those with no food, because they are never empty. You'd have a choice of staying on your own latitude line until the last minute, which would make your path longer, but forage better. Or turn early and angle in, but so is everyone else.

The trailing edge is where it really gets interesting (behind my priest-wagons). Full-on disaster mode all the time. Strife and discord would be the rule. A few seconds of killing another traveler for food (or to be food) is far faster than trying to dig edible roots in land that has been trampled for months. Exhausted people staggering along abandoning their possessions, with bands of daring outlaws swooping about. And maybe small raids from the dark (demons under cover of medium-duration darkness spells, etc).

At the dawn edge, you could have caches of wealth hidden and abandoned by people who were falling behind. You could even stash supplies planning for a war next year. Build a cache, fill it with weapons, hide it. When you got back to it next year, you pickup your equipment and raid a neighbor. Of course a lot of these will end up abandoned.

You'd tell where you were in relation to the dark by the position of the sun. If it's late afternoon all the time, you need to pick up the pace.

Imagine a secondary shadowy night. Like an eclipse, it has a variable-appearing path, only last minutes to maybe a couple hours, and comes every few weeks. Just enough time for vampires and other creatures of the dark who have buried themselves for protection from the sun to pop up above-ground and catch several days worth of meals in one frenzy.

Pretty much exactly how I was envisaging it. I like the cache idea.

Best part about the dusk and dawn edges is that you've got rather cool names for the factions that hover around the edges :smalltongue:

Ooooh. I like that. Eclipses turn the whole thing to sugar. And finding hidden tombs for creatures who cbf'd moving. Look at that. You can just a pop a dungeon in anywhere, can't you. Darn useful things they are.

[Jack_Simth]

Friggin' spellcasters :smallsigh: Looks like low magic campaign, or (preferably) limited access to EzyTravelTM spells.Can also be done legitimately with a light horse and no magic. 60 foot move. 1 hour of hustling causes it no pain. 7 hours of walking, likewise. Meanwhile, because the base move of the creature is twice that of a human, it covers the 48 miles that would take a human a 16 hour forced march. You'll have to travel fairly light, but this is doable.

[Red Rubber Band]

Can also be done legitimately with a light horse and no magic. 60 foot move. 1 hour of hustling causes it no pain. 7 hours of walking, likewise. Meanwhile, because the base move of the creature is twice that of a human, it covers the 48 miles that would take a human a 16 hour forced march. You'll have to travel fairly light, but this is doable.

Indeed. It's something that I want as a legitimate choice. But spellcasting trivialises by doing it for more people in half the time. And they never have to worry about a lame leg. Cause they just "poof" another into existence.

[Ogh_the_Second]

I think the premise is great for a short campaign, but you would have to let go of far more conventions to make this make any sense. (Yeah, I know, sense is overrated.)

If this is/always was the "natural" condition of this world, there will be no strongholds (well, maybe dwarven underground ones, or something like that), if only because human civilization would never evolve beyond hunter-gatherers (-robbers). Who is going to herd animals or plant crops if you move all the time? Who is going to build a house, a village, a town, a stronghold in 6 months that can reliably withstand demonic hordes?

Further, remaining in a hunter-gatherer society, this would preclude all sorts of stuff. Metal-working will be rare, if existent at all. Nobody's got the time to develop any but the simplest technology. Nobody's going to make paper or papyrus. Nobody is going to develop a significant monetary system. There will be no land ownership, government, universities, wizard schools, printing, weaving, carpentry, trade guilds. There has to be a continuous land area around the globe, because there is no time to learn how to build sea-going vessels. Nothing but an endless journey, with stone-age technology.

I remember reading a sci-fi book 25 years ago with a similar premise. 'Civilization' existed of one race of solitary sentient feline-like creatures biologically made to cover large distances, and that was it.

[Crake]

I feel like after a bit of time people would have started banding together to be able to make it further together. Over time people who could manage to would have managed to get mounts of some kind. After taming their first few mounts, they may have been able to get far ahead enough of the darkness to put together a caravan. Once they manage that, they are now travelling without worry of themselves getting exhausted, but this now puts extra strain on the horses. So they get more horses, and run them on rotating shifts. As their caravan grows, they would begin having space for extra things, such as growing their own crops on farm caravans, or places for the common folk to learn, such as schools. Over time these people would begin to become specialised, with generations of educated children, they would have people who become masters at breeding strong resilient horses, and others who become great engineers, able to make lightweight yet sturdy carriages, inventing things like ballbearings to make the carriages easier for the horses to pull. Some may even begin to learn how to harness the power of the sun, and develop solar powered engines. The caravans would begin to lose the need for horses, and would be constructed together to make small towns on wheels, powered by the eternal sun above them. As these moving towns cross paths with other towns, they would merge, either peacefully or forcibly, eventually becoming larger and larger until they become towering MORTAL ENGINES yup, just like the book

[Keltest]

Another question is how long has this been going on? If its been centuries since it started, the nomad tribes are going to be pretty well adapted to it at this point. Even a low-magic setting they would probably have found themselves a minor wizard or something who can help keep people moving.

[SangoProduction]

Indeed. It's something that I want as a legitimate choice. But spellcasting trivialises by doing it for more people in half the time. And they never have to worry about a lame leg. Cause they just "poof" another into existence.

Well, you see...If this is something that everything on the planet is doing (unless they are stronghold-born, I won't question how the strongholds got there, perhaps philanthropic cheetah-folk) then it would be biologically trivialized, if this went on for more than a few generations. This is because, while there may be room to evolve to be faster, there is a evolution floor, where if you drop below a certain speed and endurance, you died and were out of the breeding pool.

Unless this thing suddenly picked up pace, as you said, everything would have adapted, and it would be more of a background concern than likely anything that the tribes have seen for themselves...and so they stop to greedily consume the forage that's not taken by other tribes because the path is too dangerous...and die, not believing in the demon cloud until it's too late.

[ExLibrisMortis]

This thread is a nice read. And now: psionic horses!


Champions of Valor has a section on specific breeds of horses. Particularly promising are the Calimite, Dambraii, and Raurin breeds. All of these have at least 70' speed and +2 constitution compared to a regular light warhorse. The Raurin also gets +2 strength.

The Dash feat, from Complete Warrior, increases your speed by 5', but only in light armour or no armour, and not carrying more than a light load. However, most horses only have two feats, and I prefer Endurance to this, thematically.
The Quick trait, from Unearthed Arcana, costs you 1 hp/HD but gives you +10' speed.
The Speed of Thought feat, from the Expanded Psionics Handbook, increases your speed by 10' while psionically focused, as long as you're not wearing heavy armour. The feat requires 13 wisdom, but hey - light warhorses actually have 13 wisdom. Fancy.
The Freedom mantle, from Complete Psionic, gives you a second 10' boost when psionically focused. A horse probably can't take this (sadly), as you need to be an ardent (or pick up an ACF for another psionic class).

You can try to breed a naturally psionic Raurin light warhorse, with the Endurance and Speed of Thought feats (replacing Run), and the Quick trait, for a total move speed of 90' at 19 constitution, and the ability to carry 600 lb at that speed (or 900 if a heavy load isn't heavy armour). With +4 on Concentration checks, it'll take the horse a while to focus (DC 20), but it should normally never have to lose focus.

Hustling for the first hour, followed by 7 hours marching, gives 81 miles per day. Switching horses every 2 hours - dealing 1 point of damage to each horse, which it recovers while resting - gets you 144 miles per day.

[atemu1234]

I would assume that the main purpose of strongholds is to protect pregnant women and small children.

Probably to protect everyone.


You can take 10 on ability checks too, so no houserules are required.



What about Traveler's Mount?



I've heard that the Elder Evils book includes a section with penalties for sleep deprivation, but that may be related specifically to the Elder Evils.

Best to assume Elder Evil only, as the ability damage involved is ridiculous.

[Red Rubber Band]

If this is/always was the "natural" condition of this world, there will be no strongholds (well, maybe dwarven underground ones, or something like that), if only because human civilization would never evolve beyond hunter-gatherers (-robbers). Who is going to herd animals or plant crops if you move all the time? Who is going to build a house, a village, a town, a stronghold in 6 months that can reliably withstand demonic hordes?

Well, you see...If this is something that everything on the planet is doing (unless they are stronghold-born, I won't question how the strongholds got there, perhaps philanthropic cheetah-folk) then it would be biologically trivialized, if this went on for more than a few generations.
I don't believe that they would have to build a stronghold within 6 months. There will have been generations of people doing this. At some point in time, someone would have thought that working for the future would be a good idea.
Not once have I said that the demons/devils/whatever will annihilate literally everything in their path, bringing mountains low and scorching the earth bare. Say, for example, that the hordes had a singular, overriding need to feed on life and had little to no interest in anything else. The nomads come back after the night passes and there's only small amounts of collateral damage to the tools and foundations. This was, for the record, my initial thought of what the horde would be like.
Hell, if I was really stuck for a story I could say a Wizard did it. In fact, having a Wizard (or Druid or Cleric) reach mid to high levels (with a peculiar selection of spells, mind you) could accomplish a lot in a much, much shorter period of time.

As for crops I'm sure finding something that can be planted and harvested within 6 months wouldn't be all the hard. Perhaps there are families that make their way to the front of the pack, set up shop for a few months and plant crops, then harvest said crops before dusk and sell them to others as they make their way back to the dawn.
Their horses would have to be incredibly resilient, and their crops would have to sell for a pretty penny, but if there's been generations of this then a whole societal structure will have sprung up to accommodate it. This could also feed into the "a Wizard did it" story, as they would need some way to keep the crops fresh for extended periods of time. And, surprise, they have just the magical item to do that. Why? I don't know, that's not my current problem and I'll cross that bridge when I come to it.

Edit:

Probably to protect everyone.

Just on this, and apologies to Bucky for not responding to this sooner. I think strongholds would be a last resort for normal people.
Darkness would be a terrifying thing for people growing up in these conditions, and not something they would subject themselves to willing. I see the stronghold as places for the crazies who want to fight, and those who would be caught out if they did not seek shelter. Incredible amounts of psychological stress would accompany someone every day that they stayed within the stronghold.

[Jowgen]

Considering everything's constant travel, large portions of the earth would have been virtually steam-rollered by the never-ending migration of everything. It would probably look like the world was full of river-beds running in parallel to the equator. Rain would be the main enemy of things, as that would cause massive flooding on these pathways, so people would have to sit that out on high-ground.

As for making the continued existence of civilization feasible via constant travel, I think things like magical/undead/psionic mounts are terribly inefficient. All you need is that one great magical treasure I wrote a sig'd handbook about:

Talisman of the Disk

Using the unlimited disks/day, large groups of people and their stuff can move at the speed of the fastest creature in the group that can activate said talisman. Eyeballing it, I think 1 per 50 people (a clan or large family?) should suffice, but might be more. Things get a lot easier if you increase the caster-level of the talisman to give it more range, weight and duration (level 8 for 45 ft radius, 800 lb/disk and 8 hour duration seems good). All they need is one creature capable of using it that is fast (lets say a raven or pseudodragon familiar) and they can haul themselves around comfortably.

EDIT: Also, most things would have the quick trait, high Con and possibly the Rapid Metabolism feat. As per Elder Evils, a creature can stay awake for 1 day per Con modifier (min 1) before it gets fatigued. Same number of days till exhaustion. Then comes drive-ya-crazy wisdom damage.

[Shackel]

I do kind of like that idea of magic "trivializing" some parts of it; some communities could have a high number of casters, yet might only have a very small number of strongholds. They stay for 4-5 months, then pack up their things and book it at insane speeds all the way to the next stronghold, and the next, and the next. Perhaps this caste has grown so settled in this pattern, that if any of the strongholds are actually taken out--if they experience the hardship of the others, basically--their society could practically collapse.

[Red Rubber Band]

I do kind of like that idea of magic "trivializing" some parts of it; some communities could have a high number of casters, yet might only have a very small number of strongholds. They stay for 4-5 months, then pack up their things and book it at insane speeds all the way to the next stronghold, and the next, and the next. Perhaps this caste has grown so settled in this pattern, that if any of the strongholds are actually taken out--if they experience the hardship of the others, basically--their society could practically collapse.

After thinking on Jowgen's post, this was along the same vein as what I was thinking. Having 3 different strongholds (used to be more but time has a way with things) that they occupy during the day for as long as feasible. They then hustle to the next stronghold and on and on. But this way of living has left them bereft of their former abilities.