Last Rites - Velen
Location: Bridge north of Blackbough
Quest Giver: Old Woman
Other Requirements: Complete Defender of the Faith
This quest is given to you by an Old Woman who can be found north of Blackbough (just across the bridge). If you've not completed the Defender of the Faith quest then this quest will be unavailable to you; this woman only starts appearing with this quest once you've finished that one.
From where you accepted the quest you will want to travel a tad bit to the northwest where the Magic Lamp marker is on your map - right next to the Pellar's hut. Place the ring that the old lady gave you on the gravestone here and then use your Magic Lamp if you got it from Keira earlier in the game to see a brief conversation between the ghosts.
Return to the village and you'll meet the old lady's grand daughter, she'll tell you that her gran has been dead for years. Apparently you spoke to a ghost! Either way the quest completes here, that's all there is to it.