Ring of Grey
Get a large amount of money either through a duplication glitch or normal game play, then go to Skingrad and speak to the Orc butler in the castle. You may need to raise his disposition first. Purchase the empty house from him, then go to Colovian Traders and buy the upgrades for the house. You may not need every one, but you can buy them all. Go to the house and go to the very top floor to the master bedroom. When you enter, there will be a bed around the corner to the left. Go around the bed and find a chest on the floor by the wall on your right side, and a bookcase on the back wall. Jump on the chest and then on the bookcase. Look to the left and there will be a scroll on a ledge behind where the bed is located. Read the scroll to receive a riddle. Go to the very bottom floor to what seems to be a wine cellar. There will be a column in the middle of the room with garlic hanging from it. If you look above it on the rafters, there is an hourglass. Pick it up to complete the quest. You will get many precious stones and the Ring of Grey, which has +5 to several abilities, including Sneak, as well as Detect Life 50 ft. This will help you see where all people are, therefore making it easier to avoid detection.