The Saltplague

Origin

The Saltplague is, perhaps, the most horrible disease known to mankind. During the time of Salt, it is said that the Mourning Brother plotted against the Bled Mother by creating animosity amongst the other creators. One such creator, known as the Sister of Apocrypha, surmised a plan to cause great suffering amongst those who were the most devout to the Bled Mother and her creation, Andrytus. The Sister's plan was to sew suffering amongst mankind through disease. Whilst many of her diseases faded after humanity found ways to treat them, one such sickness never faded: the Saltplague.

"And the flesh of thine nose and ears shall harden into chalk and fall from the face. The skin shall become rough and flake like the Salt before. Fingers and toes shall snap like brittle twigs. Eating will become difficult and sores will weep with the humors about the body. Death, O poor soul, is inevitable."

- The Book of Humors, Passage 33

Also known as Saint's Bane, the plague is said to only affect the most pious amongst the clergy and that it was not something to lament. The commonfolk, however, oftentimes had outbreaks of the Saltplague that would destroy entire villages. As such, those that carry the plague were forced to uproot and become nomadic. Their lives would be entirely reliant upon the alms granted by those who pitied them. 
The disease itself takes years to cause such drastic effects as the loss of cartilage in the nose and ears though people are utterly horrified at the sight of such an effect to the point that those with the plague choose to forever cover their faces. Covering the face with a mask of wood, linen, or metal is a sign that someone bears the plague and that people should maintain their distance from them as the disease is believed to be highly contagious. 

Treatments

The Saltplague is not particularly treatable. Those with the plague bleed rather easily and, as such, oftentimes have trouble closing wounds. Many of what are called "Saint of Salt" cover the entirety of their skin in linens soaked in honey or medical poultices to ease the pain. Many of those afflicted with the plague can live long lives if they are careful but progressively grow less and less able over time. The oldest known Saint of Salt was said to be in her fifties and contracted the plague in her thirties, suggesting that she survived with the disease for two decades.