Diseases
A plague ravages the kingdom, setting the adventurers on a quest to find a cure. An adventurer emerges from an ancient tomb, unopened for centuries, and soon finds herself suffering from a wasting illness. A warlock offends some dark power and contracts a strange affliction that spreads whenever he casts spells.
A simple outbreak might amount to little more than a small drain on party resources, curable by a casting of lesser restoration. A more complicated outbreak can form the basis of one or more adventures as characters search for a cure, stop the spread of the disease, and deal with the consequences.
Disease as a Plot Device
A disease that does more than infect a few player characters is primarily a plot device. Diseases can affect any creature, and a given illness might or might not pass from one race or kind of creature to another. A plague might affect only constructs or undead, or sweep through a halfling neighborhood but leave other peoples untouched. What matters is the story you want to tell.
Some particularly dangerous diseases might threaten player characters more significantly, such as being infected with an Illithid tadpole or contracting a disease empowered by the fey. Diseases of such magnitude might create whole campaigns to cure them, or they might be something characters have to try their best to avoid.
Disease Severity
Each disease has multiple levels, called Severity. Accumulating severity causes additional effects based on the amount of severity a creature has. Each disease starts at severity 1 when it is gained. If a creature that already has a disease suffers another effect that causes them to gain that disease again, its severity increases by 1 instead. Other effects might also directly cause a disease to increase in severity, such as Arcane Rot being fed magic.
Creature suffer the effects of their disease's current level of severity. For example, if a creature's Cackle Fever has a severity of 3, it suffers just the effects of that disease's third stage.
Each disease has an upper limit to its severity. Gaining more severity than that limit causes an incredibly adverse effect. Typically this effect is death or a natural end to the disease, but certain diseases (such as an Illithid Tadpole Infection) have a different effect.
Recovering from a Disease
Certain effects, such as the Paladin's Lay on Hands or the Lesser Restoration spell, reduces a disease's severity, as specified in the effect's description. All effects of a disease end on a creature if that creature's disease is reduced below 1 severity.
Infection Types
Diseases can be contracted in the following ways. Some diseases might be contracted in multiple ways, as described in the effect's condition.
Airborne. These diseases can be contracted by breathing in gases, powders, spores, or similar. The disease's description notes how easily it can be contracted in this way.
Contact. Contact with certain creatures and objects might cause a character to contract a disease. The likelihood of contracting this disease through contact is listed on that creature's statblock or the trap's description.
Ingestion. If a creature swallows food, water, or some other material infected with this disease, they suffer its effects.
Injury. Some injuries caused by creatures or traps might inflict a disease. The likelihood of contracting this disease through injury is listed on that creature's statblock or the trap's description.
Magical Diseases
Some diseases are magical, making them much more difficult to cure. Most effects that would instantly cure diseases instead have no effect on these diseases, and effects that would reduce their severity are half as effective. For example, if an effect mormally reduces a disease's severity by 2, it instead reduces the severity of these diseases by 1.
Nonmagical Diseases
Bluerot
This disease target humanoids. While afflicted with bluerot, a victim grows grotesque blue boils on their face and back. This disease is carried by Undead.
Bluerot is an Injury disease. The disease's boils manifest ld4 hours after being infected, regardless of its severity. Symptoms include a fever and tingling in the extremities.
Bluerot Effects
| Severity | Effects |
|---|---|
| 1-3 | The infected creature's Constitution and Charisma scores to decrease by ld4 each (minimum of -3). They are also vulnerable to Radiant damage and gain the ability to breathe underwater. |
After gaining more than 3 Severity, a creature naturally overcomes Bluerot.
At the end of each long rest, an infected creature makes a DC 12 Constitution saving throw. On a success, the victim regains 1 point of Constitution and l point of Charisma lost to the disease. If the infected creature regains all the points lost to the disease, it is cured. On a failed saving throw, the victim takes 18 (4d8) Necrotic damage as the boils burst and spread. A creature reduced to 0 hit points by this damage cannot regain hit points until the disease is cured, though it can be stabilized as normal.
Cackle Fever
This disease specifically targets Humanoids, although gnomes are strangely immune. While in the grips of this disease, victims frequently succumb to fits of mad laughter.
Cackle Fever is an Airborne disease. Any Humanoid creature that starts its turn within 10 feet of an infected creature in the throes of mad laughter must succeed on a DC 10 Constitution saving throw or also become infected with the disease. Regardless of whether it succeeds or fails this save, the creature can't gain this disease from that particular infected creature again for 24 hours.
Cackle Fever Effects
| Severity | Effects |
|---|---|
| 1-3 | The infected creature gains one level of Exhaustion that can’t be removed until the disease is cured. If an effect causes the creature great stress, such as entering combat or being Frightened, it must succeed a DC 13 Constitution saving throw. On a failed save, it takes 1d10 Psychic damage and becomes Incapacitated with mad laughter for 1 minute. The creature can repeat the saving throw at the end of each of its turns, ending the mad laughter and the Incapacitated condition on a success. |
After gaining more than 3 Severity, a creature naturally overcomes Cackle Fever, and is immune to its effects for 24 hours.
Illithid Tadpole
The Illithid Tadpole targets mainly humanoids with the goal of creating new Illithids. Infected creatures lose their teeth and hair, their skin becomes slimy and purplish, and they sprout tentacles from the front of their face.
Illithid Tadpole is an Ingestion disease. It must be implanted directly onto the brain, which it achieves by crawling behind creature's eyes, where it begins the transformation.
Illithid Tadpole Effects
| Severity | Effects |
|---|---|
| 1 | The infected creature gains one level of Exhaustion that can’t be removed until the disease is cured. |
| 2-3 | The creature gains two levels of Exhaustion that can’t be removed until the disease is cured, in addition to those gained from this disease's Severity 1 effect. |
After gaining more than 3 Severity, over the course of a minute, the creature's hair and teeth fall out, their skin turns purple, and they violently sprout tentacles from their face. They must immediately make a DC 20 Charisma saving throw. On a failed save, they become an Illithid under the DM's control. If a creature succeeds its save, it gains the Illithid prestige ancestry, provided it meets the prerequisites.
If an effect causes the creature great stress, such as entering combat or being Frightened, they must succeed a DC 12 Intelligence saving throw or gain 1 Severity in this disease.
Sewer Plague
Sewer Plague is a generic term for a broad category of illnesses that incubate in sewers, refuse heaps, and stagnant swamps, and which are sometimes transmitted by creatures that dwell in those areas, such as rats and otyughs.
Sewer Plague is both a Contact and an Injury disease. When a humanoid creature is bitten by a creature that carries the disease, or when it comes into contact with filth or offal contaminated by the disease, the creature must succeed on a DC 11 Constitution saving throw or become infected. It takes 1d4 days for sewer plague’s symptoms to manifest in an infected creature, regardless of its severity. Symptoms include fatigue and cramps.
Sewer Plague Effects
| Severity | Effects |
|---|---|
| 1-5 | The infected creature suffers one level of Exhaustion, and it regains only half the normal number of hit points from spending Hit Dice and no hit points from finishing a long rest. At the end of each long rest, an infected creature must make a DC 11 Constitution saving throw. On a failed save, the character gains one level of Exhaustion. On a successful save, the character’s Exhaustion level decreases by one level. If a successful saving throw reduces the infected creature’s level of Exhaustion below 1, the creature recovers from the disease. |
Sewer Plague neither ends nor worsens as a result of gaining more than 5 Severity.
Sight Rot
This painful infection causes bleeding from the eyes and eventually blinds the victim.
Sight Rot is an Ingested disease. A beast or humanoid that drinks water tainted by sight rot must succeed on a DC 15 Constitution saving throw or become infected.
Sight Rot Effects
| Severity | Effects |
|---|---|
| 1 | One day after infection, the creature’s vision starts to become blurry. The creature takes a −1 penalty to attack rolls and ability checks that rely on sight. At the end of each long rest after the symptoms appear, the penalty worsens by 1. When it reaches −5, the victim is Blinded until its sight is restored by magic such as the Lesser Restoration or Heal spells. |
Sight Rot neither ends nor worsens as a result of gaining more than 1 Severity.
Sight rot can be cured using a rare flower called Eyebright, which grows in some swamps. Given an hour, a character who has proficiency with a herbalism kit can turn the flower into one dose of ointment. Applied to the eyes before a long rest, one dose of it prevents the disease from worsening after that rest. After three doses, the ointment cures the disease entirely.
Magical Diseases
Aboleth Gills
Aboleth Gills is carried by Aboleths that forces creatures to undergo a harsh metamorphosis, gaining slimy skin and needing to be in water to survive.
Aboleth Gills is a magical Injury disease. The disease has no effect for 1 minute regardless of its severity, and can be reduced or removed by any magic that cures disease. After 1 minute, the diseased creature's skin becomes translucent and slimy, and it gains the disease's effects.
Aboleth Gills Effects
| Severity | Effects |
|---|---|
| 1-5 | The creature can't regain hit points unless it is underwater, and the disease can be removed only by the Heal spell or another disease-curing spell of 6th level or higher. When the creature is outside a body of water, it takes 6 (ldl2) Acid damage every 10 minutes unless moisture is applied to the skin before 10 minutes have passed. |
| 6-10 | The creature can't regain hit points unless it is underwater, and the disease can be removed only by the Heal spell or another disease-curing spell of 6th level or higher. When the creature is outside a body of water, it takes 19 (3dl2) Acid damage every 5 minutes unless moisture is applied to the skin before 5 minutes have passed. |
Aboleth Gills neither ends nor worsens as a result of gaining more than 10 Severity.
Arcane Rot
Arcane Rot affects magic users who enter areas of great magical decay, such as areas where magic is broken, or upon interacting with raw magical power. It is characterized by a rotting of the flesh fed by magic.
Arcane Rot can be transmitted by any means. When a creature capable of casting at least one spell comes into contact with infected material, be it in the air, contact with an item, ingestion, or by injury, it must succeed a DC 15 Constitution saving throw or contract Arcane Rot.
Arcane Rot Effects
| Severity | Effects |
|---|---|
| 1, 2, . . . | The creature's maximum hit points are reduced by 5 for each level of severity it has in this disease. If its hit points would be reduced below 0 by this disease, it can't be revived by anything short of a True Resurrection spell. |
Arcane Rot has no upper limit to its severity.
If any spell is cast by a creature infected by Arcane Rot, or if they are affected by a spell, the severity of their Arcane Rot increases by 1.