More than 400 years have passed since the Tribunal (Vivec, Almalexia and Sotha Sil), have lost their connection with the source of their divinity, the Heart of Lorkhan, and their powers diminish.
Mehrunes Dagon, the daedric prince of destruction, who invaded Mournhold 1300 years ago, and was banished by Almalexia and Sotha Sil, is to return.
TO START THE MAIN QUEST
Go to Ebonheart. There is a female breton mage, named Asciene Rane. She may transport you to Mournhold. Once there, head to the Temple Reception, and talk to Fedris Hler, the Temple steward.
DISCLAIMER:
you may play this mod even if you have already completed the original Main Quest because most of the Npcs, creatures, and places, have been made anew.
If you have already found some quest items (Barilzar's Mazed Band, Trueflame and Hopesfire), with this mod, they'll turn to common enchanted items. You have to find the new ones during this new main quest.
http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=9004