In Sickness and In Health

Diseases are one of the things that tend to be ignored in fantasy world-building.

That’s not really all that surprising, of course. Most aspects of fantasy tend to focus on the role of sapient beings – be they deities, dragons, or even human(oid)s – because that speaks most closely to potential players. People, be they players or GMs, want to think about the impact that their character(s) will have on the game world, and so new worlds are built around what big men have done, rather than focusing on environmental determinism (of which the impact of diseases on the trajectory of societies is an aspect).

Even when raised, this is typically hand-waved away under the idea that the presence of magic (which most fantasy worlds tend to have) would make diseases a non-issue. Why would villages succumb to a plague when clerics can just prepare remove disease and have that be that? On its face, that does seem to be a good explanation. But in fact, it depends on the game rules in question (for example, the Pathfinder version of the remove disease spell linked previously is notably less effective than the 3.5 version of the spell). Even then, things aren’t nearly as cut-and-dried as they might otherwise be.

For those who have it, page 20 of Pathfinder #8 – Seven Days to the Grave has an interesting sidebar that touches on this for D&D 3.5. Titled “Where Are All the Healers?” it breaks down what the game rules say about city demographics and what they say about resources that can be brought to bear during an epidemic. The end result is that, in the event of a large-scale outbreak, magical healing resources will be too few to effectively combat a widespread disease. (Note that you won’t find this sidebar in the Curse of the Crimson Throne reprint of this particular Adventure Path.)

In the case of diseases, their large-scale impact on history is attributable to different peoples having evolved different degrees of resistance/immunity to particular illnesses. While things like the consequences of the Black Death are easy to take note of, other aspects of diseases on the course of history are subtler. Specifically, they played a major role in large-scale migrations, either abetting them or inhibiting them depending on the varying levels of immunity possessed by native peoples and immigrants. Just look at what happened when Europeans traveled to the Americas for a large-scale example of this. Less notable, but no less important, are instances where immigrating people were depleted or wiped out by diseases that native populations had already grown accustomed to.

So what would all of this look like if we tried to hard-code it into an RPG, such as the d20 System?

Unfortunately, that’s not very easy to do. The game rules treat characters’ ability to resist diseases as a function of a single statistic: their Fortitude save. This number is universal, not taking into account issues of an individual’s genetic ancestry giving them high resistance to some diseases and severe vulnerability to others. Rather than trying to modify the system to represent a more nuanced approach to this, we’ll simplify what we’re trying to portray.

Disease Vulnerabilities by Race

The following table (with most of its racial disease vulnerabilities randomly determined) represents a cross-indexing of the seven standard races with the eleven diseases presented in the Core Rules. Where a given intersection has “–” listed, the standard rules are used should a character of that race encounter that particular disease. In this way, the standard listings for each disease presume that someone fighting it off has an evolved resistance to it via their genetic ancestry.

In this case, the idea of “human diversity and adaptability” is played up; humans enjoy no particular vulnerabilities to any disease, having encountered all of them numerous times over in their spread across the game world. Other races, however, aren’t quite so fortunate. Each of the remaining races has some illnesses to which they’re not very resistant, due to their people only encountering them in relatively recent times. This means that those diseases are more virulent for them, and so pose a greater threat.

Disease	Humans	Elves	Half-elves	Dwarves	Halflings	Gnomes	Half-orcs
Blinding Sickness	—	A	—	—	B	—	—
Bubonic Plague	—	—	—	B	C	—	—
Cackle Fever	—	—	—	—	—	B	A
Demon Fever	—	—	—	A, C	—	—	—
Devil Chills	—	A, B, C	B	—	—	—	A
Filth Fever	—	—	—	—	B, C	C	—
Leprosy	—	—	—	—	A	A, C	—
Mindfire	—	—	—	B	—	—	B, C
Red Ache	—	—	—	C	—	B	B
Shakes	—	B, C	C	—	—	—	—
Slimy Doom	—	A, C	A	—	—	—	C

Key: A = Increase DC by +4; B = Increase damage by +1 per die (e.g. filth fever now deals 1d3+1 Dex damage and 1d3+1 Con damage); C = Increase necessary number of saves to cure by +1.

The above table works not only as a simplified way of adding a new wrinkle to the presence of diseases in your game, but also contains intriguing suggestions as to what the above connotes about various races in the game world. Notice how half-elves seem to have acquired many of their human half’s resistance to diseases that are otherwise devastating to elves? By that logic, do half-orcs having so many disease vulnerabilities mean that orcs have even worse diseases ravaging them (and that’s why they’ve been pushed back in the face of human and demi-human expansion)? And why do gnomes and halflings have similar levels of vulnerability to certain diseases and not others?

Try making your own such table, and see if a focus on diseases spurs a healthy new interest in designing your campaign world!