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.

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 Fortitude or become infected.

It takes d4 days for sewer plague's symptoms to manifest in an infected creature. Symptoms include fatigue and cramps. The infected creature suffers one level of Exhausted, and it regains only half the normal number of Vitalitys from spending Hit Dice and no Vitalitys from finishing a Long Rest.

At the end of each Long Rest, an infected creature must make a DC 11 Fortitude. On a failed Contesting Roll, the character gains one stack of Maimed.

On a successful Contesting Roll, the character's Maimed stack decreases by one.

If a successful Contesting Roll reduces the infected creature's level of Maimed below 1, the creature recovers from the disease.