Crusader Kings II: The Reaper's Due

Little remains of those settlements where the Black Death has passed through. Hasty burials make a mockery of the sacraments and set a feast for the crows. Once prosperous provinces have been laid waste, and the lord of the land hides away – secluded in his hilltop fortress, hoping the plague will pass him by. Wiser princes took precautions, and didn’t waste the revenues from more prosperous years.
But, in time, all must pay The Reaper’s Due.

The Reaper’s Due adds a host of new mechanics centered on the Black Death and other world shaping epidemics. Lock your gates to keep the plague from infecting your court, even if it means cutting yourself off from your suffering citizens. Peace and good management will see your provinces reward you with greater wealth and manpower, but constant war and disease may depopulate your countryside.
The Reaper’s Due introduces many new systems and features to what is already the richest medieval tapestry in gaming:## The Black Death:

New additions to epidemic system include this super destructive disease and a new map mode that track the expansion of deadly illnesses.## Court Physicians:

This new position for learned courtiers opens up a series of events tied to the diagnosis and treatment of diseases with medieval tech.## Hospitals:

Slow down the spread of epidemics by investing in these outposts that care for the sick and infirm.## Prosperity and Depopulation:

Watch your provinces thrive under your careful attention and degrade under the pressures of diseases run amok.## Seclusion:

Take a page from the Masque of the Red Death and hide yourself away with your court as plagues ravage the countryside.## And even more:

New physical traits, new events chains and a host of smaller changes.

Source: Steam Store Description