Dungeons & Delvers: Diseases

In our bi-weekly A Sundered World campaign the players are searching for sunlight in the corpse of Skoll, the wolf that devoured the sun during the Sundering.

They've crawled up through her radius or ulna (doesn't really matter which), and have now entered one of the lungs, which I'm calling either the lung labyrinth or bronchial badlands. Not sure as both are catchy.

One of the things they've encountered are streptococcus zombies: they look and mostly act like normal zombies, but are really controlled by immense bacteria like puppets. These corpse-puppets are necessary for them to survive (they reside within them while dormant), and also function similar to bodyguards.

When destroyed the bacteria ruptures, and characters caught in the ensuing gas cloud risk infection, which ended up happening to two out of three characters (they tried quickly donning masks beforehand: thought it was pretty clever so gave them a saving throw bonus).

I figured this might happen (if not then but later when they encountered other things), so I had to determine at least more or less how I wanted to handle diseases, which meant a trip down edition lane to see if I could find something that worked, something that was close but not quite what I wanted, or if I'd just have to figure it out myself.

2nd Edition Dungeons & Dragons was a complete bust. I couldn't find any hard rules on diseases or even example diseases. Best I could find was in the Monstrous Manual, where it stated that some rats carry diseases, but I couldn't find any mechanics behind them. In Rules Cyclopedia you have to make a save versus poison, otherwise you have a 1-in-4 chance of dying in 1d6 days.

In 3rd Edition you made a Fortitude save if you were exposed to a disease. Success means there's no effect, but if you fail there's an incubation. All of the default diseases take at least one day, and most only day a single day, with devil chill's giving you 1d4 days before it kicks in.

Once the incubation period is over you took ability score damage, which was pretty nasty since you only recovered a single point per day, though only having your Constitution reduced to 0 could kill you (anything else just made you completely incapable of doing anything for various reasons).

Using blinding sickness because it's the only common one between editions, after a 1d3 day incubation you suffered 1d4 points of Strength damage, and if you take 2 or more damage have to make another Fortitude save to avoid permanent blindness.

Every day you got to make another Fortitude save, and if you failed you suffered ability score damage again. If you succeeded nothing happened, but you only recovered from a disease if you made two saves in a row (or three in the case of devil chills).

A healer could help you out by making a Heal check. You still had to make a save, but got to pick your save roll or the Heal check, whichever was better. Of course magic could just fix the whole thing in a snap (and in the case of mummy rot was mandatory).

Fairly good start. I don't like that everything can feasibly be overcome in a couple of days, though, and the effects also don't match up with the myriad of symptoms and complications diseases can impose.

4th Edition introduced the disease track, which I think was based off a condition track from Star Wars: Saga Edition. How diseases kicked in varies: if a monster that carries the disease hits you, you don't make a save until after the encounter is over, and even then it was only one save regardless of how many times you got exposed. Otherwise the disease could make an attack against your Fortitude Defense (basically a reverse save).

Each disease has an initial effect, an unnamed "middle" effect, and a final state. If you get hit with a disease you start out on the initial effect, and then every time you take an extended rest (what 5th Edition renamed to long rest) you make an Endurance check to see if you improve, stay where you are, or get worse (there's a separate DC for each). If you get worse you move right on the track, and if you get better you move left.

If you improve to the cured space, well, you're obviously cured. Here's a picture of blinding sickness's disease track:

While I like that there are effects beyond stat damage, I don't like the idea of a character potentially rubber-banding between stages 1-3. Also it's very likely you'll be cured the very next day so long as you've got someone trained in Heal, or various abilities that give bonuses on stat and/or skill checks.

5th Edition only provides three example diseases, and they each vary quite a bit: Cackle Fever kicks in after 1d4 hours, while Filth Fever needs 1d4 days. You make a Constitution save after a long rest for both, but with Cackle Fever if you succeed the saving throw DC is reduced by a random amount, while Filth Fever's exhaustion level drops by one. Once Cackle Fever's saving throw DC reaches 0 you recover, and once you're no longer exhausted from Filth Fever you recover.

Sight rot (assuming this is just blinding sickness by another name) is less forgiving: if you fail the save to resist infection, the next day you're -1 on all checks that rely on sight. The penalty automatically increases by 1 each day (no save allowed), but once you're at -5 you're instead blinded. The only way to prevent it is to use a specific type of medicine three days in a row.

If I had to choose one, I'd go with 5th Edition since incubation isn't so predictable, like 3rd Edition incubation varies, and like 4th Edition the symptoms aren't just stat damage. Best bits from a few editions, but I still think it needed a few tweaks

Big one is variable duration. Not everyone that gets sick remains sick for the same amount of time. I'm guessing D&D tries to convey this with needing a certain number of saves to stave it off, but I think in most cases it's too quick: in 4th and 5th Edition you can get an infection from rat bites and shake it off the next day (two in the case of 3rd Edition)!

So for example if you get exposed to a disease and fail to shake it off, you could remain sick for something like 3d4 or 2d6+4 days. Some diseases might automatically tick down without the need for a save, or allow a save and have it tick down faster if you succeed. For those you will recover, it's just a matter of time.

Others would be harder to shake off. Each time you long rest you make a Fortitude save: if you succeed then the duration is reduced by a day. If you exceed by 5 or more it is reduced by two days. If you fail then nothing happens unless you fail by more than 5, in which case the duration is increased by 1 day. You could also mess with this: maybe you need to exceed the DC by 5 or more to reduce the days, and failure increases it by one or more days.

The effects could also be randomized, determined by rolling on a table (possibly modified by your Con or some other ability score), or based on the overall duration (the longer it lasts, the harder you got hit). This is because not everyone that gets infected with something presents the same symptoms. Some diseases could have an effect where if the duration is increased to a certain point, or lasts a certain number of days it gets worse, like how untreated bronchitis can lead to pneumonia.

Now the effects of disease can be almost anything you can think of, especially once you factor in supernatural creatures, magic, gods, other planes of existence, etc. In addition to ability score reduction (which are fine for portraying symptoms like muscle weakness, loss of balance and coordination, and difficulty concentrating), you could impose persistent conditions such as Blinded, Slowed or Confused.

You could also include situational effects, like if a character moves too quickly they have to make a Fortitude save to avoid a severe coughing fit, effectively Dazing or even Stunning them for a turn (would also prevent the use of bard or wizard spells).

More supernatural diseases could cause a character to gradually become Invisible, ethereal, and eventually completely fade from existence. They could grow scales or mouths on their body, flesh could turn into bark or stone (perhaps an infection from nearly being petrified, or recovering from it), eyes could bug out like a beholder, limbs transform into tentacles, hunger for human flesh (after a brush with a ghoul), body could gradually freeze regardless of the weather, they could even randomly teleport to a nearby location (or another plane entirely).

So here's the Delver-ized version of blinding sickness:

BLINDING SICKNESS
Exposure can occur from drinking contaminated water, or coming into contact with contaminated people and objects (most often clothing) Some vermin are known to transmit it, too.
Incubation Period: 2d4+4 days.
Duration: 2d6+2 days
Saving Throw DC: 13
Symptoms: On the first day after the incubation period the afflicted creature's eyes become itchy and sensitive to light, eyelids can swell and there might be discharge: they suffer a -1 penalty to all checks that rely on vision. On the second day this penalty increases to -2, and it is reduced to -1 once the disease has only 1 day left.

If the disease lasts for five days the target is Blinded until the disease is cured or the afflicted creature recovers. If the disease lasts for a total of seven days, then even after recovery the afflicted creature still suffers a -1 penalty to all checks that rely on vision due to corneal scarring (if the creature is again afflicted with blinding sickness, temporary and permanent penalties are cumulative). If it lasts nine or more days, however, then the Blindness is permanent.

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