Derulbaskul
Adventurer
Firstly, I would echo the earlier comments about purchasing When The Sky Falls and using meteors... almost liberally. 
Secondly, IMC, the great underlying theme is always the battle between Shar and Selune. Selune wants Toril to live and grow; Shar wants everything returned to primordial darkness. Shar's most devoted followers are made up of a custom prestige class, the Dark Nihilist. They have many of the powers of the ruin priests of WTSF... including the ability to summon a meteor after three tendays of sacrificial ceremony. I have attached the prestige class for you to see what I mean, particularly how the Dark Nihilists turn a symbol of hope into a thing of destruction.
Anyway, my campaign is developing into a running battle between the PCs (and other forces across Toril) with Shar's patsies. She has offered the power of the Shadow Weave to Cyric, Talon and Kiaransalee, amongst others... and all for a very small price. Along the way they are beginning to uncover knowledge of the Shadow Weave... and will shortly discover the power of the Dark Nihilists in an ancient tome dating back to the time of the Creator Races.
The orcs, too, are but pawns of Shar. The shamaness, Black Lorog, is actually a disguised annis cleric of Shar who is moving the orcs into position to spread strife and destruction throughout the North.
Blah, blah, blah... I think you get the picture. In due course, the party may or may not stop the Dark Nihilists in their area but they will hear stories of widespread destruction across the rest of Faerun as cabals of Dark Nihilists successfully call down meteors on major population centres... which will also turn people against Selune in particular because of the way the meteor first appears (see the attached file for an explanation).
Of course, I haven't decided how far and how dark to take the campaign but the seeds are there to utterly destroy Toril and usher in the time of primordial darkness that Shar so wants.
Cheers
D

Secondly, IMC, the great underlying theme is always the battle between Shar and Selune. Selune wants Toril to live and grow; Shar wants everything returned to primordial darkness. Shar's most devoted followers are made up of a custom prestige class, the Dark Nihilist. They have many of the powers of the ruin priests of WTSF... including the ability to summon a meteor after three tendays of sacrificial ceremony. I have attached the prestige class for you to see what I mean, particularly how the Dark Nihilists turn a symbol of hope into a thing of destruction.
Anyway, my campaign is developing into a running battle between the PCs (and other forces across Toril) with Shar's patsies. She has offered the power of the Shadow Weave to Cyric, Talon and Kiaransalee, amongst others... and all for a very small price. Along the way they are beginning to uncover knowledge of the Shadow Weave... and will shortly discover the power of the Dark Nihilists in an ancient tome dating back to the time of the Creator Races.
The orcs, too, are but pawns of Shar. The shamaness, Black Lorog, is actually a disguised annis cleric of Shar who is moving the orcs into position to spread strife and destruction throughout the North.
Blah, blah, blah... I think you get the picture. In due course, the party may or may not stop the Dark Nihilists in their area but they will hear stories of widespread destruction across the rest of Faerun as cabals of Dark Nihilists successfully call down meteors on major population centres... which will also turn people against Selune in particular because of the way the meteor first appears (see the attached file for an explanation).
Of course, I haven't decided how far and how dark to take the campaign but the seeds are there to utterly destroy Toril and usher in the time of primordial darkness that Shar so wants.
Cheers
D