First off, this is a great idea for a campaign setting.
Regarding the flooded dwarven ruins, as a player I would feel disappointed if there weren't a section requiring us to explore and, potentially, fight underwater. So definitely include some dark, flooded catacombs populated by carnivorous horrors.
Actually, playing off the ideas of a couple other posters, how about the cause was a brilliant composer who has sequestered himself away for 50 years, furiously writing and discarding various compositions. Any individual piece would have been a masterpiece, but nothing has satisfied the lofty vision that his mad genius demands of him. In a fit of mad desperation, he performed a ritual that created a connection to the elemental plane of water in order to create an endless rain over the area that would inspire him to create a composition the likes of which the world has never seen. Maybe his muse that inspired him to go to these lengths is some kind of shadow fey.
1) Maybe 2) Definite maybe 3) No. I would discard any idea that boils down to "a wizard did it." I like the composer idea because it's a more uniquely Gothic premise, and with a campaign setting this unique, you want to make sure that the core secrets underlying your world aren't derivative.I haven't quite figured out what caused the rain yet. Currently, I'm operating on the idea that it's a long-standing curse, but if anyone's got a really creative idea, I'd love to hear it. Other ideas I've discarded is that it's a mad composer who needs the rain to finish his grand masterpiece, or it was a defense mechanism by a wizard to allow him to fight invisible creatures.
Regarding the flooded dwarven ruins, as a player I would feel disappointed if there weren't a section requiring us to explore and, potentially, fight underwater. So definitely include some dark, flooded catacombs populated by carnivorous horrors.
Actually, playing off the ideas of a couple other posters, how about the cause was a brilliant composer who has sequestered himself away for 50 years, furiously writing and discarding various compositions. Any individual piece would have been a masterpiece, but nothing has satisfied the lofty vision that his mad genius demands of him. In a fit of mad desperation, he performed a ritual that created a connection to the elemental plane of water in order to create an endless rain over the area that would inspire him to create a composition the likes of which the world has never seen. Maybe his muse that inspired him to go to these lengths is some kind of shadow fey.