Disease and illness

Simple rules for getting sick

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Diseases are a great way to make fantasy feel grotty and horrible. A complex subsystem for modelling it doesn’t suit me though, so I’ve been using a quick and lean procedure to bring the grimdark vibes.

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Player characters can be exposed to disease factors, like:

• A bite from an animal.

• Consumption of contaminated food.

• Crowded areas where there is already a prevalence of illness.

• Exposure to a harsh environment (e.g. marshes, jungles, tundra).

We’re going to try to roll a d6 above a certain number to see if characters are infected by the disease. The chance of catching a disease increases by one per disease factors involved. For example, using a d6:

Roll above 1 to avoid disease if they’re in a crowded area (only one disease factor).

Roll above 3 to avoid disease if they’re in a crowded area (the first disease factor), in a harsh environment (the second disease factor) and they’ve eaten contaminated food (the third disease factor).

Remember to telegraph disease risk. This should be a problem for the PCs to grapple with, not just a tax. A smart player immediately washes an animal wound or avoids crowds in a plague stricken city.

Don’t deploy this mechanic for every single exposure. It doesn’t matter if a PC is bitten twice or three times by a giant rat, make one roll. If a character is infected, roll a d12 to see how many hours it is before the PC notices their first symptom.

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Symptoms

The nature of the disease is up to you, but something to note is that the ‘path’ of diseases and illness is often unexpected. Use a table of general symptoms that have mechanical impacts, and randomly generate the progression of the disease (including a ‘no new symptom’ result). Roll on it daily for the infected character. Here’s an example table.

Disease Symptoms (d20)

1: Cannot regain HP.

2: Lose 1HP per day (despite any HP recovery).

3: Movement speed halved.

4: Disadvantage/bane on physical checks.

5: Disadvantage/bane on mental checks.

6: Carrying capacity reduced.

7-20: No new symptom.

Each new symptom increases the ‘stage’ of the disease. It starts at stage 1, which can progress to stage 2 and so on. If you roll a symptom the character already has, you could find a way to make it worse, or just re-roll. Stage 7 can be death if you like.

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Recovery

A character only becomes aware they are sick when the first symptom hits. Good factors to require for recovery in general are:

• Some kind of medical care (e.g. medicinal herbs, cleaning of a wound) specific to the ailment or disease.

• Rest. Galloping on horseback whilst sick is not going to help you feel better, but walking with a stage 1 disease should be fine (right?)

• Food and water.

• Reasonable climate.

When these are met on a given day, have the character make a roll relating to their physical health (which may be at a disadvantage). This should be done before you check if the disease advances. If they succeed, reduce the disease by 1 stage. If it hits stage 0 they have recovered.

If they fail, make a roll as usual to see if the character gains a new symptom.

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That’s it

Simple rules for disease and illness that you can bolt onto pretty much anything. Go have fun getting players worrying about flu more than monsters.

This is great for everything from Cairn to Mork Borg, and works for modern settings too like in Cy_Borg or Liminal Horror.

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