Mantle of Woe Location - Morrowind
Location: Rimhull, on Solstheim
Requirements: Bloodmoon Expansion Pack
Video: How to get the Mantle of Woe
The Mantle of Woe is worn by Tymvaul, a necromancer on the continent of Solstheim who is found in the dungeon of Rimhull, southwest of the Skaal Village. If you speak with Lassnr at the Skaal Village he'll give you a quest by the name of Tymvaul in the Well which has you enter Rimhull and find his son, Tymvaul. Doing this quest will get you an additional reward for finding Tymvaul so it's recommended you pick it up. Lassnr will also give you the key to enter Rimhull if you choose to use the entrance closer to the Skaal Village.
As usual for Elder Scrolls games you don't need this quest to obtain the Mantle of Woe item. Inside Rimhull you'll find Tymvaul and (if you're currently on the quest) you'll be given a few options. Every option you can pick will get you the Mantle of Woe from Tymvaul - if you choose to kill him just loot it from his body instead. Choosing option #2 (I've been sent by your father. Take off that robe and end this madness. Your father loves you, Tymvaul, and only wants you to be happy) in the list of dialogue options will get you the best reward for this quest.
Return to Lassnr in the Skaal Village and tell him what happened with his son; if you chose option #2 you will receive 5 Snow Bear Pelts as an additional reward.