Swamp Cankers

Oozing Blisters galore
Those who are wounded and wandering throughout the swamps much make sure they do not enter particularly stagnant sections. Swamp water is filled with microorganisms seeking to enter through cuts and lacerations of any would-be adventurer or traveler with any chance they get. Those with open wounds run a serious risk of infection.

The disease works slowly, but can very quickly become debilitating if left unchecked. With the first 24 hours, the infected individual may not even know they are infected. By 48 hours, the infected individual will start to grow painful blisters the size of a human's thumbnail along the infected areas. By 72 hours, the blisters begin to burst and spread the infection, which continues to new parts of the body as well as to new hosts.

This continues until the host grows feverish and suffers from dehydration. If left unchecked, the hosts entire body may become covered in burst blisters that ooze a thin, murky sludge.

Infection and cure?
A creature who is missing hit points suffers the risk of infection in normally two ways: Contact with an infected creature or entering into stagnant swamp water infected with the microorganisms.

Those who are missing HP and come into contact with the infection or infected water must make a DC 12 Con save. On a success, the creature is unaffected by the disease. On failure, the creature becomes diseased and begins to show symptoms two days after infection. At the end of each Long rest after the third day of infection, the creature must make a DC 12 Con save. On failure, the creature takes 1d6 necrotic damage as the blisters begin to burst. The number rolled is then subtracted from max health and the new total is used until the disease is cured. If the creature drops to 0 from this damage, they die. On success, the creature takes no damage and is one step closer to being cured.

Curing Swamp Cankers requires three consecutive, successful DC 12 Con saves (only one is made at the end of a long rest) over the course of three days. A creature proficient with Medicine can make a DC 12 Medicine check on the infected creature to grant advantage on its next Con save. Alternatively, a creature proficient with an Herbalism Kit can make a cure using an uncommon plant that grows at the bottom of swamp lakes called "Gruumsh Tooth." This cure requires a DC 12 Herbalism Kit check to create and costs 50gp. If the creator fails the check, the resources are wasted.