>>43287018Permanent Rain is a nice touch - no winds, no lightning, just an endless soft pattering of water falling.
I like to have BBEGs have some kind of summon lesser mook ability - with an evil water elemental, have him awaken the rivers and lakes as elementals in their own right.
A decent BBEG should be capable of wiping out something the characters care about more than their lives - get them invested in the campaign world some how, with either the last paragraph here:
>>43285847 or the last line here:
>>43282964 showing up as recurring themes - the Moon hangs in the sky, vivid red with its fury, or the Mountains begin to tumble, marching against the sea, but their time has past, and the swelling waters swallow up the roiling stones.
It can be as a vision, the words of a crazy old dwarf, a persistent icon (every mountain pass is blockaded by rocks whenever the party goes there), or whatnot.