Nestled within the city of Owlshade is a walled-off enclave, filled with everyone afflicted by the plague. This miserable patch is ruled over by Husmanna, a cadaverous sorcerer who blasphemously extended his own life centuries ago.
Basilica is deadly back door into Owlshade (or whatever fantasy city of your own design you insert it into). Using treatments only he can provide, Husmanna adopts the afflicted from wealthy families, extending their lives. For centuries, he has cultivated his influence over the noble families this way.
The Basilica would make a suitable addition to a fantasy city where the players are looking for a seedy way to buy influence.
There's a downright apocalyptic angle to this adventure, however. If adventurers are careful it won't trigger, but this has the potential to completely explode.
As always, the text and art are released under CC-BY-NC thanks to generous Patrons.. like Andy!