Worlds of Design: Pestilence & Plague

Plagues have made a big difference in world history, and may in your fantasy world. In the course of studying military and diplomatic history over most eras I’ve encountered a lot about this frighteningly frequent occurrence.


Picture courtesy of Pixabay.

The condition of the people was pitiable to behold. They sickened by the thousands daily, and died unattended and without help. Many died in the open street, others dying in their houses, made it known by the stench of their rotting bodies. - Giovanni Boccaccio (1313-1375)

Absent widespread healing or vaccines, plagues have historically been a fact of life, one of those things you hoped to avoid but sometimes could not. The effects were far-reaching. In building a world, you can ignore plagues, just as you can ignore famines and extended droughts that can bring down empires and even civilizations, or you can incorporate them into the history of your world. Whether that will increase the immersion of your game depends on your players. I’m going to talk about some characteristics of plagues and how you can incorporate them into your world building.

Lethality and Randomness​

The Black Death of the 14th century (also known as the Pestilence or the Great Mortality, peaking in Europe1347-1351) helps provide a guide to the lethality of historical plagues. Depending on the affected location, between a quarter and a half of the population died. Plagues in general are random, so that there were locations such as Milan, Italy that were essentially free of the Black Death. If you look at a map of the effects of the Black Death, you can see this variability for yourself. Some plagues almost always killed anyone who was infected, while others saw many recover and possibly gain immunity. Plague usually affected everyone, young and old.

It Kept Coming Back​

Historical plagues didn’t just peter out or disappear never to be seen again. They kept coming back in waves, with periods (often many years) in between that were relatively plague free. Obviously, there were no vaccines, and even if the plague were one that you became immune to after contracting it, there were people who had not yet contracted it, plus younger people born since the last outbreak. In some areas forms of plague continued to occur periodically into the 17th (and rarely 19th) century!

After the fact, a plague could radically change the nature of society. After the Black Death, the standard of living rose significantly. Ordinary people ate better because there was a lot more food (especially meat and fish) in relation to the population. The poorer land went out of cultivation and reverted to nature, for lack of farmers - but that meant on average people farmed more productive land. Laborers were paid more because there was a shortage of labor. Plagues had far-reaching social effects, e.g. widespread persecution of minorities and lawlessness. Effects were so pronounced that the time of the Black Death is sometimes regarded as the end of the Middle Ages.

The Fall of the Western Roman Empire​

A fairly recent explanation of the weakness and fall of the Western Roman Empire is that it was depopulated by plagues 180-250 CE. This is rarely touched on in the literature of the time (perhaps because it was so common), but archaeological investigation of Roman cities shows a great contraction of the lived-in area, indicating a much lower population long before the actual failure of the Empire. This is not the only reason of course. When you talk about the fall of Western Rome, the question is always why didn’t Eastern Rome (what we now call the Byzantine Empire) fail? Eastern Rome had a much higher population, far more cities, and could suffer a series of plagues more readily than the West.

Yet the Byzantine Empire suffered a great plague, possibly as bad as the later Black Death, in 541-549 (not disappearing entirely until the 700s). This doomed Emperor Justinian’s efforts to reunite the full Empire, for lack of manpower, though he did recapture much of Italy, North Africa, and even southern Spain before the plague.

In pre-Roman-domination times, a plague killed many Athenians including their leader Pericles (d. 429 BCE); some historians believe his death doomed the Athenians in the Peloponnesian War with Sparta.

What This Means for Your World​

Fantasy worlds are different from the real world in the availability of magic that can cure diseases. The question is always how much healing is available in comparison to the size of the population? We could say that the elites (such as Pericles) are much more likely to survive a plague thanks to magic, as opposed to historical plagues where anyone from an Emperor on down (including several Roman emperors who died from pandemics) was just as susceptible as anyone else.

As you build the history of your world a plague can make a huge difference, especially a plague as bad as the Black Death or the Justinianic Plague. In a fantasy world with many intelligent species, a plague might affect only one species to its detriment. When someone asks why there are so few of a particular species, an answer might be disease. Even today birdwatchers observe that house sparrows rapidly disappeared from much of the countryside, possibly because of disease.

Your Turn: How have you implemented plagues in your campaign?
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Lewis Pulsipher

Lewis Pulsipher

Dragon, White Dwarf, Fiend Folio


I was designing a Homebrew campaign right when the pandemic hit and it revolved around a plague. No one wanted to play that idea in that moment heh.
Curiously, during the first months of the pandemic, all the versions of the boardgame Pandemic sold out everywhere.

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Getting lost in fantasy maps
Mystara’s Savage Coast region had the Red Curse that people just got by being within The Haze that covered the region. Gave people abilities, but could afflict them with permanent mutations if they didn’t keep a specific metal in their possession that slowly depleted in affectiveness, needing replenishment. The poor who could not afford the material sometimes lived in outcast communities.

The closest TSR might have come to having an entire setting around a plague-like affliction.
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The idea of a heavily depleted population in an urban area is very interesting. The plague could even be recently cured, and you could have a city where several districts are now deserted, allowing gangs and bandits to rule these lawless areas. It would allow you to do a campaign where city intrigue and dungeoneering/heavy combat are perhaps right on the each other’s doorsteps. 🤔


So the trick with magic as far as plagues go. Obviously everyone immediately looks to Lesser Restoration, a 2nd level spell that can cure disease. But it can be argued that 3rd level clerics still aren't a dime a dozen, and only 2 uses a day might not stop a full virulent plague.

However, the real anti-plague magic, is Detect Poison and Disease. This is a 1st level RITUAL, and lasts for 10 minutes, and will instantly tell you if someone is diseased. So you can literally have a 1st level acolyte priest just stand in the square, and have people walk past him, and he can instantly determine if they are diseased and need treatment and/or quarantine. As a ritual he can use it all every day.

So how might that affect your world building?

  • You should expect any decent town or city to have a priest at the front gate with Detect Disease on. They would stop any diseased person from entering the town (whether there was plague or not, that would be good practice). Its such a trivial cost that every town worth its salt should do this if it has continuous commerce from other places.
  • If plagues are a thing, its either because there are diseases that get past detect spells, or....perhaps in your world people do not know that diseases are contracted from other people....therefore quarantine methods are not utilized. So yeah the clerics can tell someone is sick, but other than wait for the greater authority of their god (aka lesser restoration) there is nothing that can be done. You might even use this as an intentional angle, allowing religions to maintain higher authority as "only the gods can cure disease", which was a common belief in medieval times.
  • You might use this in a world with high clerical authority. Religion is the law, and if a land does not want to obey the high cleric, well that's fine....we will just withdraw our disease curing services. Lets see how long you last when your people get plaques and mine don't.


A suffusion of yellow
I played in a game that involved a plague and quite frankly it was extremely boring for the PCs. People dying of disease in a world without germ theory isnt very heroic and a 'quest to find the cure' is a one off adventure not a campaign.

Natural disasters are slightly better due to usually being a lot more dynamic and thus providing a 'survival impetus' to the interactions. Disasters also provide the whole depopulation impact on society too and I've used major typhoons and subsequent flooding as a way to devastate a community - with PCs asked to batten down the hatches, save the citizens and rescue sheep from flood waters:), Afterwards the city was faced with refugees who had come in from the rural hinterlands seeking shelter, they also had to recover the dead (to stop outbreak of disease), rebuild the destroyed port and decide what to do now that a quarter of the old commercial ward had a new river running through it.
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The one plague I've done in my games was a Slaadi/Zombie plague. In my campaigns, Slaadi are truly chaotic (not the color coded posers in the core books!). They are constantly changing, and so every so often you will just get this insanely weird and crazy Slaad.

In this case, the Slaad disease turned people into zombies, and the zombies could spread the plague further. There was a small percentage chance that anyone infected would instead turn into another Slaad. So the party had to deal with a host of undead and Slaad in several areas of the country.

Disease (of any kind) in my game is the result of a Disease Spirit. Disease Spirits "ride" their hosts with various deleterious effects. They range from Minor Disease Spirits to Plagues. It works pretty well. It takes the (real world) science out of it and gives a different spin to disease. More of a horror / supernatural invasion at the pandemic end of things.


Disease (of any kind) in my game is the result of a Disease Spirit. Disease Spirits "ride" their hosts with various deleterious effects. They range from Minor Disease Spirits to Plagues. It works pretty well. It takes the (real world) science out of it and gives a different spin to disease. More of a horror / supernatural invasion at the pandemic end of things.
Really, in a D&D setting, I think this is the way to do it.

I eliminated real world science in my game :) No gunpowder, gasoline / internal combustion engines, miracle medical drugs, etc. In 1974 my original players were board / miniature wargamer history nerds :D They would have been blowing up dragons and building machine guns and tanks in no time... so bye bye science, hello the elements air, earth, fire, water, and my number five - spirit. Saved me from explaining just how difficult all those "simple" ideas would be to develop too. Changing how the world works can account for the rather wonky game physics as well.

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