Advanced Diseases and Diagnoses

Adventuring is dangerous business. Dungeons are filled with monsters, tricks, and traps. The wilderness is littered with small armies of orcs and bandits, and strongholds ruled by hostile high-level characters who demand jousts or tribute in the form of magic items, or send player characters on quests via geas to obtain such items.

But even adventurers who overcome these challenges have another, unseen threat to contend with: disease! The AD&D DMG has detailed rules for handling the contracting of diseases, although Gygax claims that the "system does not attempt a specific treatment of a subject which is beyond its scope and purpose":

From the AD&D DMG, CHARACTER AGE, AGING, DISEASE & DEATH, page 13

I will clarify what exactly Gygax means by this shortly. For now, let's get into the non-"specific" but nonetheless very thorough handling of disease in AD&D.

First, we are told that the DM should generally check whether each player character has contracted a disease once a month, once a week if conditions are favorable, or each time a player character is exposed to a disease carrier:

We are then provided with the percentage chances of contracting a disease each time the check is made:

With a base 2% chance and no situational modifiers, we can expect a player character to contract a disease, on average, once every 50 months, or a little more than 4 years, which seems a bit low. 

In particularly dangerous circumstances - the character is already diseased or infected with parasites (I'll get to that later), is in a crowded, filthy environment (a city, encampment, ship, or siege) in a hot and moist swamp or jungle, and is of venerable age - the chance increases to as high as 14%. On average, such a character would contract a disease about once every seven weeks (remember that under ideal conditions, the check is made every week instead of every month). 

If there is an outbreak in such circumstances and the poor character is being exposed to disease carriers left and right, the chance increases to 24%, meaning the character will contract a disease roughly every four encounters (assuming, I suppose, that there are somehow multiple diseases at play, which seems unlikely in an epidemic scenario). That would be a terrible situation indeed!

Hopefully, the character is a paladin or monk, as both of these classes are immune to disease - in the monk's case, beginning at 5th-level. Speaking of 5th-level, that's also when clerics and druids get access to the cure disease spell, so it's safe to say that disease is, for most adventuring parties, one of those low-level setbacks which is eventually trivialized by access to more potent forms of magic. It is a "lock" for which the players will eventually acquire a "key", so to speak.

And that's great news, because diseases are really annoying! Here is the table you roll on to determine what area of the body is affected by a disease, the disease's occurrence, and severity:

Here we see what Gygax meant when he said that AD&D "does not attempt a specific treatment of" diseases. I take this to mean that specific in-world diseases are not described in detail, but rather generally, and in terms of actual game mechanics. If you want your AD&D diseases to reflect those found in the real world, apparently OD&D Supplement II: Blackmoor has you covered.

Instead of that, Gygax provides some general guidelines regarding occurrence and severity:

And then descriptions of the game mechanics pertaining to each type of disease:

Diseases are brutal. A diseased character is incapacitated for anywhere from 1 to 4 weeks, may suffer permanent penalties to their ability scores, lose the function of body parts, and even die. 

A character who contracts a disease has a 1% chance of it being a brain/nervous system disease, which has a 37.5% chance of being terminal, which has an 8% chance of killing them in one hour. That's a .03% chance overall, so it's very unlikely to happen, but it could. Imagine being the unlucky player whose character drops dead before they even know that anything's wrong with them. People who complain about save or die traps and spell effects in AD&D clearly have not read about the diseases!

If my math is right, a character who contracts a disease has a 13.125% chance of contracting a terminal case - and that's before accounting for modifiers to the severity die roll. Fortunately, having a high (or even average) Constitution score significantly mitigates this risk:

Disease goes hand in hand with parasitic infestation, which the DM must also check for each month or week (in favorable conditions), or whenever the player character is exposed to a carrier:

Parasitic infestation also gets its own percentage chance of occurring:

In particularly nasty situations - the character is exposed to filth (i.e., is in the city, probably), eats improperly cooked meat, drinks polluted water, and is in a swamp or jungle environment - the chance is as high as 16%, indicating infestation once every 6 months, weeks, or encounters with a carrier.

Here is the table of infestation types and severity:

A character who is infested with parasites has a 15.625% chance of developing a terminal case (there are no modifiers to severity for parasitic infection). Assuming an unmodified disease severity roll, parasitic infestations are slightly more deadly than diseases.

A character who dies from disease or infestation (most likely) continues to suffer the effects after being brought back from the dead:

This all to say nothing of lycanthropy, which in AD&D is a disease...as well as a curse? It is treatable with both cure disease as well as remove curse. Lycanthropy however is a much larger subject and is beyond the scope of this post (I will likely write about it some other time).

Aside from lycanthropes and monthly/weekly checks, what else can spread disease/parasitic infestation? Let's start by looking at the Monster Manual.

Cerebral parasites are, of course, parasites. They siphon energy from psionics:

The demon Demogorgon's tentacles inflict a disease which can cause limbs to rot and fall off, or permanently reduce a creature's maximum hit points unless cure disease is administered within 6 rounds:

Another demon, Juiblex, has the spell-like ability to cause disease (the reverse, evil version of cure disease):

Infestation by ear seekers can be thwarted by cure disease if cast with 4-24 hours of contact. Otherwise, the host is 90% likely to die:

Violet fungi's branches inflict flesh rot similar to Demogorgon's tentacles, but that of violet fungi takes effect in only one melee round, although a saving throw is allowed (the mechanical effects of the rot are not elaborated upon, so I'm not sure how it's meant to function in game terms - perhaps similar to that of Demogorgon):

Gas spores, when exposed to flesh, infest a creature with tiny rhizomes (parasites) which kill within 24 hours and produce more gas spores unless a cure disease is applied:

Green slime is a "strange plant growth" which turns exposed creatures into more green slime within 1-4 rounds. Its vulnerability to cure disease suggests it is itself either a disease or parasite, though it isn't clear which:

A bite from a giant leech has a 50% chance of causing a disease which kills in 2-5 weeks (here a mischievous leprechaun from the adjoining column, unaware of or perhaps immune to the danger, is seen riding the leech):

Yellow mold, when attacked, releases spores which infect the lungs and kill instantly unless a saving throw is made. A cure disease and a resurrection cast within 24 hours can save the afflicted:

The touch of a mummy inflicts a rotting disease which kills in 1 to 6 months, permanently reduces a creature's Charisma score by 2 each month, negates cure wounds spells, and reduces the rate of natural healing to 10%. The disease causes the bodies of those killed to rot away, and such individuals cannot be brought back to life unless cure disease and raise dead are applied within 6 turns:

The neo-otyugh inflicts disease, although the method of transmission and the exact type isn't specified:

Presumably, like the standard otyugh, its bite has a 90% chance of inflicting typhus - yes, typhus specifically, for some reason (perhaps the neo-otyugh transmits neo-typhus):

Typhus is, of course, a real world disease, and it affects multiple areas of the body, including the skin, gastro-intestinal organs, and brain. I'm not sure how it would be classified within AD&D's non-specific disease schema.

The bite of a giant rat has a 5% chance of transmitting a "serious" disease (is this meant to mean "severe" disease?) unless a saving throw is made. Since the specifics of the disease are not detailed, presumably the DM would roll on the disease table in the DMG:

Like the cerebral parasite and ear seeker, rot grubs are treated as parasites. Infestation is countered by cure disease if applied within 1-3 turns:

Like the giant leech, a bite from a giant tick has a 50% chance of inflicting a disease which is fatal in 2-8 days unless a cure disease is applied:

Of the monsters that cause disease or parasitic infestation, ear seekers, giant rats, rot grubs, gas spores, violet fungi, wererats, giant ticks, werewolves, and yellow mold all appear on the random monster tables for dungeon levels I thru IV, meaning that player characters will likely encounter these monsters prior to having access to cure disease. Of those, diseases/infestations inflicted by ear seekers, violet fungi, yellow mold, and rot grubs will take their course well before the player characters have a chance to return from the dungeon and treat the ailment, so low-level characters without access to cure disease should be especially wary of these threats.

In addition, while low-level adventurers would be wise not to venture into the wilderness too early, there one might find green slime (in shallow fresh water), giant leeches (in shallow fresh water and uninhabited marshes), lycanthropes (in both inhabited and uninhabited areas), mummies (in uninhabited rough terrain, hills, and mountains - undead are not encountered in deserts, for some reason, and unfortunately there are no bog mummies here), giant rats (in sub-arctic forest, rough terrain, and marshes, as well as most terrain types in inhabited areas), and giant ticks (in uninhabited scrub and forest). While all but the green slime inflict diseases which allow some time for treatment, this is of course the wilderness - who knows how far away treatment might be?

If the player characters happen to use psionics, they run the additional risk of encountering cerebral parasites, demon princes such as Demogorgon and Juiblex, and yellow mold.

It is telling that disease-carrying and parasitic monsters are more common in the dungeon than in the wilderness (dungeons are, fittingly, disease pits).

I would be remiss not to mention the dreaded beggar, which may also be a disease carrier:

Since beggars can be disease carriers, an encounter with one could be cause for the DM to immediately check to see if the player character has contracted a disease (with +10% chance of contracting the disease, according to the table at the beginning of this post) - just another hidden danger of city encounters! And don't forget that giant rats and all manner of lycanthrope will be encountered in cities and towns as well.

Evil clerics - and druids, apparently - can also cause disease by reversing the cure disease spell (druids are Neutral by necessity, but they still have access to the - evil - reverse of cure disease):

Evil clerics can also reverse the heal spell to instead harm and by doing so inflict disease:

It's not all monsters, wretched beggars, evil clerics, and the ubiquitous peril of living in the AD&D world. Cursed scrolls have a 25% chance of inflicting a disease which kills in 2-8 turns:

The periapt of foul rotting, which may appear as any "gem of small value" inflicts a rotting disease which reduces Dexterity, Constitution, and Charisma by 1 each week. When any score is reduced to 0, the character dies. The disease can only be removed by remove curse and cure disease and heal, limited wish, or wish:

Outside of avoiding hot, moist, crowded conditions, swamps, jungles, cities, encampments, ships, nasty monsters, beggars, scrolls, and gems of small value, never getting old, living in the mountains, being naturally gifted in Constitution, or being a paladin or 5th-level monk, are there any other ways to avoid diseases and parasites?

You can start by cooking your meat and boiling your water. Alternatively, a 1st-level cleric can instantly purify it for you:

Druids can only purify water (not food), for some reason:

Additionally, amber gemstones are reputed to ward of disease:

Unfortunately, Gygax immediately informs us that, actually, that's hogwash, and carrying around such a gemstone "will convey absolutely no benefit of magical nature":

This is too bad, as I quite like the list of REPUTED MAGICAL PROPERTIES OF GEMS. I really like the idea of player characters carrying around a bunch of bejeweled items (rather than selling them) in order to benefit from minor magical properties. I say if they're carrying around some amber, give them a -1% chance of contracting a disease!

The periapt of health (which looks exactly the same as a periapt of foul rotting) confers immunity to all diseases except the foul rotting inflicted by the aforementioned periapt (interestingly though, the periapt of health can be crushed into dust and sprinkled upon an afflicted character to counter the periapt of foul rotting's effects):

Finally, one possible minor benign power of an artifact or relic is to grant immunity to disease:

But you're not a paladin or 5th-level monk. You don't live in the mountains. You're of a sickly disposition, and very old. You live in a city which is for some reason built in a swampy jungle. You run into beggars on your way to the plague rat-infested ship which takes you to the dungeon full of gas spores, green slime, and violet fungi. You break for lunch and eat and drink nothing but raw otyugh meat and polluted dungeon water. You're gonna get sick. Where can you get a cure?

Cure disease is of course the obvious solution. As I mentioned earlier, it's a 3rd-level spell for clerics and druids:

In addition to being immune to disease, paladins can also cure disease (even before they gain access to the cleric spell, which isn't until 13th-level):

A psionic can use cell adjustment to cure disease as well:

If you have a disease of the eyes, cure blindness (another 3rd-level cleric spell) will help, but not if you've already lost the affected eye(s):

If you have no cleric, druid, paladin, or psionic in your party, you will have to find an NPC to help you. Cure disease costs 1,000 gold pieces:

A dungeon room containing unguarded gold contains 250 gold per level, so this is equivalent to four such rooms for a 1st-level character and one such room for a 4th-level character (that is, it is not cheap):

Remember that even if the player characters can afford this service, actually obtaining it from the NPC should still be irritating!

If you have no luck finding a human/demihuman spellcaster to aid you, you might seek out a "tribal spell caster":

It will have to be a bugbear, gnoll, kobold, orc, giant, goblin, hobgoblin, or lizard man, however, as these are the only monsters able to attain a high enough spellcasting level:

However, considering that most of these monsters are Evil, and curing disease is Good, casting these spells often will put these monsters in jeopardy with their gods and alignment:

It is probably fair to say that convincing these monsters to utilize this magic will be even more expensive and irritating than usual!

If you also have no luck finding a tribal spell caster, consider tracking down a werebear:

Or steal a night hag's periapt forged in Hades:

Failing all that, you might track down some medicinal herbs, spices, or vegetables. APPENDIX J has a detailed list of such things and their reputed medicinal benefits, which is much too thorough to get into here. In short, they can be used to treat urinary, venereal, skin, liver, pulmonary, eye, mouth, and respiratory diseases. As with gems, Gygax spoils the fun by saying, no, actually, none of this stuff actually does anything, but we don't always have to listen to the old man.

Finally, there are a few magic items that cure diseases, such as the staff of curing:

Keoghtom's ointment:

A bead of curing (found on a necklace of prayer beads):

The cup and talisman of Al'Akbar:

And as a major benign power of an artifact or relic:

All this is to say: give your player characters diseases! Make them face down disgusting little dungeon creatures. Make them ward off hoards of beggars. Introduce a plague to your next urban or seafaring adventure. Have the Evil warlord in the castle lay siege to the city and start catapulting diseased corpses inside. Make the player characters properly cook their meat, or make the cleric prepare purify food and drink. Make them spend tons of gold dealing with annoying NPCs. Make them seek out and parley with monstrous spellcasters and werebears. Make them steal from hags. Make them quest for rare magic items to ward and cure themselves (and don't forget to sprinkle in the occasional cursed scroll or gem). 

Put in them the fear of swamps and jungles, cities, ships, old age, fungi, mold, and rats, and all the unseen dangers lurking in heaps of filth, standing water, rotting wood, and the very air they breathe!