On Diseases in Orginal D&D

One small project I’m working on is writing out rules for handling disease in old school D&D. My general goal is to craft some mechanics that can work, with minor tweaking, for most any TSR era edition of D&D. Whenever possible, I want to use existing rules published by TSR. It’s not a hard requirement, and I’m willing to tweak any rules I find, but I’d at least like to start with something "official".

And I thought I was onto something, but now I don't think so at all. In doing some research on this, I found this post from Delta’s D&D Hot Spot, where he points out that the earliest rules for Diseases in D&D actually appear in OD&D supplement 2, Blackmoor.

Alas, despite Delta’s endorsement and his general enthusiasm, I don’t think these rules actually work. Let’s take a look at why.

The Effects of Being Sick

Here's a portion of the rules in question:

 

 

 

 

 

Fatality

The most straightforward effect of contracting a disease under this system is that doing so might kill your character. For each disease, Blackmoor gives a flat percentile chance that your character will die from having contracted it. Bubonic Plague, for example, has a 35% fatality rate.

What the rules don’t say, however, is when to roll for fatality. The only mention I can find related to this is the following: “Players may get cured by the local Magic User or Cleric but they must do so before the referee rolls for their death.” So, it’s important in this system to know when the fatality roll occurs, but there’s no indication when to do so.

Strength Decrease

The other effect of having a disease is that it weakens your character, literally reducing their Strength:

“During the early stages of the disease the player will lose the use of strength points based on the days they stay out of bed.”

I really like the idea of diseases decreasing your strength. However, here’s where things get a little clunky.

“… for a disease that lasts 1–5 days, each day they will lose 20% of their strength points.”

It took me a minute to figure this out, but what the rules are saying is that the GM should divide the total possible Strength damage out across the full duration of the disease. Not the duration rolled by GM, mind you, but the maximum potential duration. That’s why the example says 20%, because 20% across 5 days (the maximum duration for the example disease) adds up to 100%.

But wait, that’s not the whole picture. The rules go on to say:

“in ALL [sic] cases the percentage will be taken out of 18 strength points so 20% … [equals] three strength points (all fractions are ignored).”

If you’re confused, what the author* is saying here is that you don’t actually reduce the character’s STR by a percentage of their character’s Strength score, you reduce it by a percentage of Strength 18, which represents the maximum Strength a character can possess in OD&D.

And here’s my next annoyance with this system. If the amount of Strength a character loses from a disease is a percentage based on the disease’s maximum duration, and it’s always applied to 18…then that’s a static number. There's no reason to require the GM to math this out.

Take the example disease, which lasts 1-5 days. Let’s assume it’s cholera, since that matches the duration. The example tells us that cholera reduces the character’s Strength by 3 each day (20% of 18, rounded down). The frustrating thing is that the number here, 3 Strength, will never change for this disease. It’s always just 3. Instead of making the GM divide 18 by 5…JUST WRITE 3 ON THE TABLE.

The Math Doesn’t Actually Work

With the above in mind, I went through and did the math on all the listed diseases, thinking that would solve the problem. Alas, doing that just revealed a new issue. Before I explain, it’s important to remind the reader about a couple things from the rule that I quoted above: 

1. The author says a character will lose strength points based on the number of days they stay out of bed.

2. We're supposed to ignore fractions when we calculate the strength loss.

But what am I supposed to do with Dysentery, which lists a duration not of days, but of 1-4 weeks? Am I supposed to convert those weeks to days, so that a character loses Strength over 7 – 28 days? That doesn’t work, because following the math given in the example would mean a PC is supposed to lose 18 Strength spread across 28 days, or .64 points per day. But remember, the rules say to ignore factions (which would include decimals). So, uh, 0 Strength per day?

Maybe It’s Per Week?

Perhaps, even though the rules clearly say per day, the author meant per time unit (week, day, whatever). So Dysentery reduces Strength at a rate of 4 points per week. That checks out.

Until we consider Tuberculosis, which has a duration of 4 – 24 weeks. Now we’re talking 18 divided by 24 (if we use weeks) or 18 divided by 168 (if we use days). Either way, we're rounding to zero. Unless I’m utterly missing something, these rules don’t actually work for at least two of the diseases.

Strength Loss Doesn’t Mean Much Anyway

Even if I solve the problem above, let’s discuss what a temporary loss of Strength actually means. In OD&D as written, the answer is: basically nothing. If you’re playing a fighter, high Strength grants an XP bonus. It doesn't grant an attack bonus, a damage bonus, or do much anything else of note.

To be fair, though, Blackmoor came out after the Grayhawk supplement, which one could argue means it was meant to be used in conjunction with the expanded ability score rules:

 

 

 

 

So I guess it’s kind of important? I’m not totally angry at the idea of Strength damage for disease, but its effect really hinges on which version of old school D&D you're using.

The Disease Table Isn’t Consistent with the Other Rules

If you read the actual disease descriptions, you’ll also notice that they often contradict the stats written in the table. Looking at Bubonic Plague, for example, we can see that the % chance to catch the disease is 1%. That seems low for a disease that ravaged most of the population of Europe.

But, reading the full description of plague, it says “any person that contracts this disease will infect 90% of the people he comes in contact with.”

What the hell Blackmoor? I guess we’re meant to understand that a person has a 10% chance of getting the plague from fleas, but then a 90% chance to get it from a person who already has it. While I’m fairly confident with my interpretation here, I’m still annoyed at how awkwardly it reads.

There’s More

Honestly, these aren’t the only warts in this system that I’d need to iron out to actually use these rules. I’m not going to delve any deeper here, though, because it just isn’t worth it. While I may still use these rules as inspiration, I’m afraid I can’t do much with the mechanics. I'll dig around a bit more, but I'm not too confident that TSR gave me any rules for diseases that I can easily crib.

 

* D&D co-creator Dave Arneson is credited as the author of Blackmoor. However, there is some debate as to who wrote what part of Blackmoor, so I’ve chosen to be generic about my references to the author.