Lots of good advice Lord Zardoz, unfortunately I've done what most of you have advised me not to do. I've used the Time Travel route.
I've also done something that most good DM's probably never do... i've changed some facts about my campaign halfway through... to fit the story I now have.
I've decided against have Shar take away the sun's fire, in favor of a mad Half-Fiend, Arch-Lich who wishes to create an army of darkness to snuff out all life. The Arch-Lich has not actually taken away the sun's warmth, instead he has changed it so that it puts off negative energy. The sun is still darkened, but seen through the eyes of undead, they would see a globe of ultraviolet light which seems to empower them.
Here is why I sent them back in time. The arch lich found and destroyed the certain artifacts that would twart his plans. Now the players must find these artifacts before they are destroyed... most likely they will run into some of the Arch Liches minions while trying to accomplish this. Ultimately they will have to face him in combat... and it won't be pretty!
I've also done something that most good DM's probably never do... i've changed some facts about my campaign halfway through... to fit the story I now have.
I've decided against have Shar take away the sun's fire, in favor of a mad Half-Fiend, Arch-Lich who wishes to create an army of darkness to snuff out all life. The Arch-Lich has not actually taken away the sun's warmth, instead he has changed it so that it puts off negative energy. The sun is still darkened, but seen through the eyes of undead, they would see a globe of ultraviolet light which seems to empower them.
Here is why I sent them back in time. The arch lich found and destroyed the certain artifacts that would twart his plans. Now the players must find these artifacts before they are destroyed... most likely they will run into some of the Arch Liches minions while trying to accomplish this. Ultimately they will have to face him in combat... and it won't be pretty!