As you reach the heart of the mine, you realize the "substance" isn't a disease; it’s an intelligence. It’s been waiting for the miners to "feed" it enough greed to finally wake up. Need to refine the "Meat"?
Add side stories, like helping a local doctor find a cure or rescuing "Little Rebecca" from a corrupted butcher shop.
Create believable groups, like the Washigami Mining Co. or a cult of "Flesh-Eaters" who worship the substance.