Tetanus (MayGetRenamedLater)
Otherwise primarily known as "Lockjaw," Tetanus is a disease where the subject's muscles will tighten until the subject cannot move after developing bone-breaking convulsions. The subject has increasing difficulty breathing, eating, and performing self-care until the end when their bones have broken and caused internal bleeding, they have suffocated, or drowned from failing to physically eat or drink safely.
Ironjaws, the ever-present companions of the Mine Guardians, are named for biting their foes and prey with their large jaws. The older an Ironjaw is, the more rusted their fangs are. A bite from an Iron Beast will almost always develop this disease unless immediately cleaned with alcohol and bandaged, and even then, the patient may still develop tetanus. Other than battlefield wounds, antagonizing an Ironjaw is the most common way of acquring the "Ironjaw's Curse."
Unfortunately, unless magically or divinely treated, there is no cure. However, treatments have been recently found and have been successful in extending one's life until they can be cured via magic or divine skill. If there is no one available to cure the disease, most patients are given pain-relieving medications to ease the end.
Yikes, that's a grisly way to go!
I know right?! And IRL, rust isn't actually hiw you get it, rusty nails are just the easiest way to contract the bacteria. Though it is heavily associated with wounds and stuff. I knew it was awful, and learned it caused bone-breaking spasms if untreated. Super yikes!