Ironrot (5e Disease)
From D&D Wiki
This disease is a mysterious malady created by contact with a mutation of russet mold. The mold originated from a sort of meteorite. A subsequent strain of it had metallic properties that, when inhaled, would slowly solidify the body of another creature, turning them into a rusty iron semblance of themselves.
Thankfully the metal variant of ironrot is not too common. It is particularly dangerous to living constructs and normal constructs like warforged and even golems. It is primarily spread through touching a secretion from the spores of metal russet, commonly found in special veins of old mines. In organic beings, its spores are dangerous when inhaled.
Those who contract ironrot notice small symptoms often immediately. Organic beings develop a worsening cough, and constructs slowly find their joints rusting up. After a week's time from exposure, afflicted beings have disadvantage in all Constitution and Dexterity saving throws, as their bodies are being broken down into rust and stiff iron flakes. Two week's time after exposure usually results in the afflicted becoming a petrified statue of brittle rust, and they are considered dead and will no longer function.
Ironrot has a few methods of being treated. The first is to completely remove the body part that was exposed. Another method is to expend a 5th level spell slot to cast lesser restoration on the afflicted, or, alternatively, greater restoration. And as usual, a powerful spell like wish can remove the disease and even revive someone killed by it.