Guide:
Western central Reaper’s March, east of the entrance to Reaper’s March from Malabal Tor. East of Vinedusk Wayshrine.
You’ll find this shard inside Thibaut’s Cairn solo dungeon. Entrance to this dungeon is inside an old graveyard and it is quite far from nearby Wayshrines. It is infested with level 38 Skeletons.
The shard is in the southeastern part of the dungeon, inside a room with several stone arches.