Resolving the Plague of Black Rot
Curing the Plague
If everyone in the village is cured of Black Rot, and all locations in which the infected were quarantined have been sterilized, and all the ghouls that escaped the village have been destroyed, then the plague can be considered ended.
The Plague Escapes
However, if the players do not act quickly and they allow the plague to spread, it can quickly overwhelm the village. If at any time there are more than ten infected households, the guard will be insufficient to contain the infected. Ghouls will escape to the countryside and begin spreading a plague into both the Dileniu and Bulostioi regions. This represents a severe disaster that will effectively end the adventure - or at least lead to a new one.
In response to a plague of Black Rot, a large armed force lead by warrior-priests from the Order of Golmongarion will arrive from Bulostioi, supported by battalions from Dileniu and Prulme. Cosutanu will be razed, as will neighboring villages if there are too many infected to be easily managed. The mines, crypts and tombs will be purged and collapsed. Likely the player characters will be held accountable, and will need to face the consequences of their failures; perhaps by undertaking a dangerous quest that is as much a death sentence as a last ditch effort to contain the plague. If this is unpalatable to them, perhaps they will flee as fugitives in an attempt to escape judgement.
What happens next will be up to you.