Learn the history of Shakri-Esh. Look for the Mysterious Cave, west of the Andasreth stronghold. This mod is definitely for people who like to read and roleplay. Depending on the player decisions there are five possible endings. There is also a new armor and new weapons to obtain. The mod also adds new horns and face for an Argonian.
http://www.nexusmods.com/morrowind/mods/44625/?tab=1&navtag=http%3A%2F%2Fwww.nexusmods.com%2Fmorrowind%2Fajax%2Fmoddescription%2F%3Fid%3D44625%26preview%3D&pUp=1