From the common cold to the plague; diseases are an ever present threat in the world. Not all diseases are deadly, but generally will cause some sort of debuff, penalty, or other effect that will hinder a creature until the disease is cured or runs its course.

Primarily diseases utilize a DC for their saving throws rather than an opposed roll, though some sources may call an opposed roll, such as if the disease is produced by a creature rather than transmitted.

Disease Transmission Types

Diseases fall into one of the following categories, based on how they are transmitted; usually between contact, ingested, inhaled, or injury.

Contact: These diseases have a risk of infecting the moment the target creature comes in contact with the source of the disease with its bare skin. Such diseases can be transferred through both injury and basic contact. While not airborne these can be transferred through simple coughing or sneezing by another subject which may have a short distance it can travel to its target.

Ingested: These diseases usually have a vector through some sort of contaminated food or drink.

Airborne: These diseases can travel through the air for an amount of time for both short or long distances. This is not quite the same as contact which may require contact with something from a carrier (such as being within a distance of a cough, sneeze, or other bodily fluid); an airborne disease can simply linger in the air and travel a potential distance. For most airborne diseases they must be inhaled by a creature, usually being within a volume of at least a 10 foot cube. Unless a creature would otherwise be aware of the presence of a disease they will likely not know how to avoid infection; but a creature aware of it may attempt to hold their breath; gaining a 50% not having to make a save each round they remain within the area to avoid gaining the disease. If a creature is holding its breath and fails the check to continue doing so, rather than suffocating it begins to breathe normally again (and is subject to the effects of the airborne disease if still in the area).

Injury: These diseases are primarily delivered through the attacks of certain creatures, requiring more than just simple contact, it must enter through a wound of some-sort.

Contracting Diseases

Once a creature has been exposed to a disease through the transmission type (such as receiving a bite from an infected creature for a contact or injury disease),

Once exposed to a disease using the listed application method (contact, injury, etc..), the disease usually will have an onset time. If the onset time is blank it means the disease has immediate effects (though this is rare for diseases). Some diseases have an onset effects causing an additional effect on the onset before any save is to be rolled.

Once the onset has occurred a creature must make a save to resist the disease. Success allows the creature to immediately be cured of the disease as it failed to take hold on its victim; failure causes the creature to take the effect of the disease and is now subject to additional saves based on frequency.

If a creature fails the onset save they must now make additional saves based on the frequency of the disease, with successes avoiding the effects of the disease each time. Each disease may have different conditions to cure, such as a single save, multiple saves, or multiple consecutive saves; the cure condition only is relevant for creatures who failed the save on the onset of the disease.

While mechanically very similar to poisons, most diseases tend to have more than simple damage for their effects and they’re intended to be long-term effects, having detrimental but not always lethal effects. Status conditions caused by a disease (such as sickened, disoriented, etc..) cannot be cured through effects that remove conditions; instead the condition lasts the listed duration (or until the disease is cured if no duration is listed); spells and effects that would remove a condition instead suppress it for 1 minute (unless it specifically says otherwise) rather than permanently removing it before the disease re-applies the status condition. Conditions may be applied by the onset effect or the effect of a failed save; with usually the onset effect having the long-term but less serious debuff and the effect of a failed save being short term but more severe.

Diseases and Weapons

A creature may attempt to cover their weapon in filth, or some other unhygienic substance in an attempt to affect a creature with it.

When dealing with an injury-based disease a creature may apply the source to their weapon, though without an ability to allow a creature to directly know if the source contained a disease the weapon only has a 50% chance of carrying a disease.

A contact-based disease carries the risk of the wielder of the weapon being exposed to the disease as well giving them a 10% chance when wielding the weapon to be subject to the disease; arrows and bolts do not carry this risk.

The disease is assumed to be Cholera or Dysentery in the case of covering their weapon with filth, though another disease may be chosen at the discretion of the GM. If the saliva or bodily fluid of an infected creature be used (such as a zombie), it will likely carry the disease of that creature instead.

A disease applied in this way only lasts 48 hours before the disease on the item becomes inert and can no longer infect creatures; though methods may exist to preserve diseases longer.

Disease Frequency

As diseases are long-term with their frequency of effects being measured in days, it may be difficult to track when the effect occurs; but more importantly diseases do not work on set schedules and as such some level of unpredictability should occur. When a disease has a frequency that specifies a number of times per day a GM should roll a d100 (%) each hour to see if the effect occurs; with at least a 1 hour cooldown between effects. For sake of ease of rounding a 1/day effect would be roughly a 5% chance each hour with the effect happening at the end of the day if it fails all previous rolls; while a 2/day can be a 10% chance; which the effect occurring automatically at the end of a 12 hour period.

This makes diseases more unpredictable and can cause their detriments to be more unfortunate in their timing, rather than something players can reliably plan around.

List of Diseases

Below is a list of common diseases; some outside factors (such as circumstantial conditions determined by the GM or spells and abilities that modify diseases) may change the DCs and the way these behave.