Elephants crossing the seas!
It is not an infectious disease, but it is a plague upon the world.
For it spawns villains. And not your garden variety villains, but epic villains, master villains of the most dangerous kind Evil Geniuses.
Pnathic sorcery has existed for ages, crudely used by magi who no idea the true forces they were fumbling with.
An article concerning the nature and role of druids in an RPG enviroment.
Plagues and other great diseases are important parts of history and some settings. They defy man and may even defy God in their swift and terrible punishment upon the body of society.
Somehow, someway, a band of gnomes learns how to be ninjas. In fine gnomish style, they open an academy to teach this art to other gnomes. Wacky Hijinks ensue. Or the gnomes become some of the finest assassins in the land. Or both.