Several iterations of my home setting ago I started digging into why "typical" TTRPG settings have such an astonishingly low population density and coming up with reasons for why that might be - inspired by this post from Blog of Holding. A plague seemed a good fit for my setting ideas given what the Black Plague and Plague of Justinian did to the world. That also spurred thinking about magical healing and antibodies and what would actually happen if you used Cure Disease in the middle of an epidemic. Does the magic confer immunity? How do? Does it stimulate the growth of antibodies, or does it just wipe out the disease? Thus was born the Red Masque plague.
The Red Masque Plague
The Red Masque plague swept across the world in the time of our grandmothers' grandmothers' grandmothers, killing three out of every five in some places. Now it returns every few years, weaker, localized, less potent, but still deadly. Still a terror. Even a suspicion of an outbreak can cause hysteria and violence as people try to quarantine themselves, escape the illness, and destroy the infection. That such panic can worsen the problem or spread the infection further is disregarded in the face of a nearly existential horror. Still worse than the disease or the reaction is what it awakens in some and the depravity it inspires in them.Stage 1. No visible symptoms beyond a slightly elevated temperature and a mild cough. Lasts d4+4 days. At the end of this stage, the infected can make a CON save if they have higher than average CON. A success means they have fought off the infection and are Red Masque Resistant.
Stage 2. Symptoms are severe and look like a bad flu. Vomiting, fever, dizziness, loss of appetite. Infection is highly contagious and airborne. Magical and mundane healing have little impact on the symptoms - often the first clue that the illness is more than a simple flu. This stage lasts d4+3 days. Every morning the subject must make a CON save or receive only half the benefits of resting. If they succeed on five of these saves in a row, they recover and are Red Masque Resistant. Otherwise, they move to Stage 3.
Stage 3. At this point the plague is in full force. Painful red boils appear around the subject's eyes and mouth, eventually spreading to cover most of the face and inside the mouth and throat. Delirium is common. The infection is only transmitted through fluids at this stage. Exhaustion, dehydration, and organ failure can occur as the disease worsens. Survivors will be left with facial scarring and potentially loss of vision. This stage lasts 2d6+2 days. Every morning the subject must succeed on a CON save or lose 1 CON. This ability reduction will not heal naturally so long as the subject is afflicted. Any heavy exertion requires a CON save against exhaustion. If the subject's CON reaches 0, they die. If they survive the full course of Stage 3, they recover and gain lifelong immunity to the Red Masque. They must roll d20 + their current CON bonus on the Red Masque Recovery table.
Treating the Red Masque Plague
In Stage 1, magic that normally cures diseases has a 66% chance to work. Mundane curatives that are not the Red Masque Vaccine will not work at all. If a sufferer is cured magically, they gain no resistance to the disease and can be reinfected normally.In Stage 2, only high-level magic can cure the disease, and then still with only a 66% chance of success. As before, being magically cured will not confer any resistance and reinfection is possible.
In Stage 3, there is nothing that can cure the infection except time. Magical or mundane treatments that improve CON or give bonuses to saves will still function normally.
The Red Masque Vaccine
There is a single mundane method of treating the plague, based on ancient formulas and ritual magics. Anyone with the knowledge can gather the materials and perform the ritual, treating ten people per day. Learning the formula and ritual requires months of study and practice, but the base materials are simple and can be gathered from almost any natural environment. Someone who receives the Vaccine while in Stage 1 is cured, and resistant to the disease for a full year, with a 33% chance to gain permanent Red Masque Resistance.Red Masque Resistance
Anyone who has survived the full course of the disease develops a natural resistance to future reinfection. They have advantage on all saves against the disease, and may make an additional save to avoid being reinfected at all. They are fully immune to the disease for thirteen full moons after gaining resistance.Red Masque Delirium
There is another, even more horrifying effect of the disease. Everyone who reaches Stage 3 of the disease has a 5% chance to develop the Delirium, a disassociative state where they hunger for the flesh of people infected by the disease. These unfortunates, unlike other sufferers, appear stronger and more resilient, and completely detached from any sense of morality or connection to others.Every night, there is a 50% chance someone with the Delirium will seek out and try to consume another infected. Every time they successfully eat infected human flesh their STR, CON, and DEX scores increase by 1, including beyond any normal limits.
If either score reaches 26, they lose their humanity completely, being overtaken by the Delirium forever. They stop saving against the Plague and recover all lost CON immediately, and will go on a rampage of cannibalistic gluttony and murder until destroyed, driven away, or forced to seek a new source of food.
There are always stories of those who seek the power the Delirium can grant and seek it out. Stories that never end well. There are also whispers that those with the Red Masque Resistance can induce it at will by eating the infected dead...
The Red Masque and Necromancy
The corpses of those who died of the plague remain infected and contagious for several weeks after death, necessitating cremation. Scavenging animals and corpse eating undead, such as ghouls and ghasts, can become new vectors for the plague and transfer it to new areas by bites, droppings, or being eaten themselves.More sinisterly, necromantic magic proves more potent when used on the corpses of the infected dead. Any spells cast that raise or create undead from corpses still carrying the plague count as being cast at one level higher than normal, and the resultant undead gain an additional HD.
