I would like elswyr, imagine a portal opens and the khajjit’s mortal enemies come in—the skaven ratmen! We as the Ratslinger of Meow must, empowered by skooma, slay the rats and close the portals. Alternatively, we launch an invasion into Naggaroth and crush the dark elves there!
The best idea, as far as I'm concerned, is to pick some geographically defined region that crosses provinces/countries, such as a stretch of coastline.