Guide:
Northeastern Easthmarch, east of Windhelm Wayshrine.
Inside The Chill Hollow public dungeon. Go to Lower Yorgrim, following the road out of Windhelm and going east and northeast. Go to the north-easternmost building in Lower Yorgrim and head northeast of it, trying to reach the small peninsula and an island next to it on the map. On your way uphill you will soon reach the entrance leading into The Chill Hollow.
Following the path to your right inside The Chill Hollow takes you to the large room in the southern dungeon. The main prize is in the corner of this room. Watch out for nearby Wispmothers, as they can easily kill you.