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.
Find and enter Thibaut’s Cairn solo dungeon.
Thibaut’s Cairn entrance
Inside one of the rooms.
Exact map location of the shard.