Back to Skellige
Outside the entrance to a crypt on Ard Skellig you’ll find two woman hanging around. They’ll call you over when they see you and ask you to kill the ghosts in the cypt so they can clip the nails of the dead.
After agreeing to help them enter the crypt and clear out the Wraiths on the first level. Head down the stairs for another 2 Wraiths and then down a final flight of stairs to clear out the last 2 Wraiths.
Destroy the breakable wall and follow the long tunnel out to an unmarked entrance outside Kaer Trolde. Turn around and make your way back through the crypt. On the first level you’ll be attacked by a Nightwraith. Kill it and then head back out to talk to the women to complete the quest.