Divirius

Divirius is the god of disease, illness and plague and is most often worshipped by witches and hags. But he does have his followers amongst all walks of life and most races. 
Unlike some of his fellow evil deities Divirius does not seek to destroy the world but he does desire that as many creatures as possible suffer from disease as he derives great pleasure from all the suffering endured by those who suffer from diseases.
The church of Divirius is outlawed in most places and worship of him is often practiced in secret. The church has in fact derived a strategy around this. Where Divirius priests travel around under the pretense of being priests of other deities and then slowly trying to infect the local populace with both actual disease but also the teachings of Divirius.
The holy symbol of Divirius is often depicted as a disease ridden rat or rats. Rats are great allies to the church of Divirius as they aid in the spread of disease and the rat is considered a holy animal by followers of Divirius.