The Blood Plague

Although there are less than thirty recorded cases, a mere four outbreaks, of the Blood Plague in the Diarchy's history the monstrous nature of this condition means it casts a shadow of fear utterly disproportionate to it's actual impact. The condition became known as the Blood Plague based on its (presumed) connection to the Blood Marshes rather than any (known) effect on the victim's blood.

Outbreak 1

The initial cases were amongst the crew of the Mikhail, an independent trading vessel operating from Dus A Thanal that is one of the few to have made the trip to the Blood Marshes far to the east. It returned to port flying yellow flags - plague - and weighed anchor well outside the sheltered harbour. When contact was made the acting Captain informed priests that eleven members of his crew - including the actual captain - had contracted some unknown disease.
Following discussions between the port authorities, the church and the secular authorities, uninfected crew members were allowed to leave and kept in isolation for several months in the local church while those infected were left on the Mikhail. Several months later the ship was set ablaze, burning the presumed corpses along with everything they had touched. The wreck of the Mikhail remains outside the harbour of Dus A Thanal, deep enough to pose no threat to shipping.

Outbreak 2

The second outbreak wasn't identified as the Blood Plague until many years after the event. Early one morning a grotesquely swollen human - deep into the third stage of the disease (see Symptoms) - ponderously walked into a warehouse on the docks, moving so slowly that opening the door, moving through it and then closing it took almost an hour according to later witnesses. Over the course of the next few hours it moved towards the centre of the warehouse. Watchful priests and soldiers kept an eye on it while discussions were held at higher levels of authority. Eventually an order was given and archers launched a volley of arrows into it, which appeared to have no effect. Further volleys of arrows were fired with similarly no effect before priests called down a column of flame to incinerate the body.
The blackened husk gave little clues and a citywide investigation was called. Eventually it was learnt that the sufferer was Abraham de Vries, a member of the Excise team working on the docks. His home was investigated and four more bloated forms were found, later identified as his wife, her lover - a sailor, one of Abraham's colleagues and a fourth who was never identified, widely suspected to be a local prostitute. The wife, colleague and unidentified were all deeper in the third stage of the disease while the sailor had already begun to ossify in the early fourth stages. The sailor was found to have returned several months ago from the Blood Marshes, the building was burnt down, Land was thanked that the monsters had been destroyed and life returned to normal.

Outbreak 3

Katrina's Dowry, an independent trading ship, was shipwrecked on cliffs around twenty miles north of Dus A Thanal, near a village called Clifftops. When locals went to salvage what they could from the wreck they found that the crew, the former crew, had been either transformed into or replaced with bone statues of hideously swollen and distended humans. The local Secular authorities had the presence of mind to seal the area and higher authorities were called to investigate. It was discovered from the logs that the ship had just returned from the Blood Marshes and tentative links were made to outbreaks two and one.
The inhabitants of Clifftops were isolated in a church. Most of them later returned home, but four didn't leading to speculation that they contracted the disease while they were on the boat and remain in Church custody somewhere.

Outbreak 4

AS determined after the fact by records and journals, Vickers Abrams, a local merchant, contracted with a herbalist to provide care for a sudden onset of joint pain. The herbalist was unable to determine a reason for the aching, and soon stiffening, joints but being of an academic frame of mind began an in depth study of the symptoms. This document: Notes on the Progression of an Unidentified Occurrence of Stuff Joints forms most of what is known about the progression of the Blood Plague.
The two of them were discovered after servants raised an alarm with the Church. Apparently instructions were received a month or so before that the merchant and his priest healer were travelling to Landhome to enter church care and the house was to be mothballed, but servants were to be sure not to enter the merchant's private suite of rooms. These instructions were followed and the house stood unoccupied except for weekly visits from a trusted servant to perform basic maintenance in expectation of his master's eventual return. On one such visit he noticed that the door to the merchant's suite stood open and a hulking figure stood in the doorway. He rant to fetch local constables.
When they returned, the figure was a few feet further from the door, down the hallway and with a bit of attention they could see it was slowly walking, slow enough that the movement wasn't visible to a casual glance. Recognising the links with previous incidences, church authorise were called and after a search of the house - revealing that the merchant had swollen up to twice his previous size and then, apparently, turned to bone, the house was burnt. Further, his records show that he had received, and catalogued, a consignment of reed sculptures from the Blood Marshes only a few days before calling the herbalist.

Symptoms

Notes on the Progression of an Unidentified Occurrence of Stuff Joints gives four distinct stages of symptoms. It is possible that there is a stage after the fourth, if so the Church may know due to, presumably, holding infected people from Clifftops. If they do, nothing has ever been publicly released.

Stage 1

...such Pain in his Joints as to render him incapable of leaving his Bed...

— Notes on the Progression of an Unidentified Occurrence of Stuff Joints

The sufferer experiences severe joint pain, apparently bad enough to near incapacitate them as any movement causes such pain. There is apparently some swelling described as "Dissimilar in every Way to that caused by Arthritis" though with irritatingly few differences mentioned. This progresses and gets worse over the course of at least two weeks - there are insufficient records to tell whether the sufferer in Notes on the Progression of an Unidentified Occurrence of Stuff Joints progressed at a normal speed or not.

Stage 2

...by Prodding and Squeezing I ascertained it was a Growth of his Bones..

— Notes on the Progression of an Unidentified Occurrence of Stuff Joints

The sufferer's bones began to grow. This causes them to grow both vertically and outwards and greatly slows their movements, though there is no record of this being painful (indeed the previous stage's pain seems to end here.

Stage 3

...appears to not need Food nor Water neither has he felt the Urge to Piss or Shit..

— Notes on the Progression of an Unidentified Occurrence of Stuff Joints

The sufferer has now swollen to one and a half to two times their previous size. However, their bones continue to grow, this growth achieved by converting flesh next to the bones into bone. The sufferer no longer needs to eat or drink as it appears the body cannibalises resources from the flesh lost to bone (or, at least, that is the current theory). By this stage their movement has slowed to the stage that it is barely perceptible to the naked eye and they are, for one reason or another, incapable of speech.

Stage 4

...

— Notes on the Progression of an Unidentified Occurrence of Stuff Joints

The last of the sufferer's body is converted to bone and they now stand as a larger than life statue made of bone. It seems likely they die some time before this final transformation but the herbalist who wrote Notes on the Progression of an Unidentified Occurrence of Stuff Joints had, presumably, advanced far enough through the disease himself that there are no notes of this final stage.

Causes

The exact causes are unknown, a combination of limited cases and limited medical science. All known cases have had some link to the Blood Marshes but the condition itself seems to be unknown to the natives there: either they have some innate immunity or there is some additional factor needed.

Social Effects

Ah, my back is killing me. It's the Blood Plague for me, make no mistake

— Overheard on the docks

Sailors lead an active and physical life and frequently suffer from sore and aching joints, as that is the first stage of the Blood Plague and many of them have visited the Blood Marshes, served alongside someone who has or similar, sailors are prone to associate any joint pain with the Blood Plague. While this is usually said with a smile or as a joke, there is an element of whistling past the graveyard to these comments and shipmates will make a point of avoiding and isolating anyone with recurring or long lasting joint pain.

Type

Parasitic

Cycle

Chronic, Acquired

Rarity

Extremely Rare