Heartwater

Being an excerpt from Planes of Disease from famous Dustmen doctor Hikelliam, who argues that diseases are a right way to offer death, saying that artificial means are not adequate to evolution.

"There are two varieties of Heartwater. The first is from the River Lethe and the other from a contaminated region in the Elemental Plane of Water. In the first case, a strange mineral present in the waters acts as a contact poison, entering the heart and diluting all blood that flows through it. After a while, the being cannot do anything but lie in bed due to excessive exhaustion."

"In cases of long exposure the brain suffers from a perversion of logic. The excessive flux of the mineral in the body results in a profuse sweat, which can be transmitted to an entire community. Feelings get hurt easily and sorrow for suffering becomes too great to bear. Treatment can be either by exposure to the waters of the Styx or by sunfly juice pressed into an ointment and applied to the skin over the course of six days, although why anyone would want to do that is beyond me."