Guide:
Northeastern Reaper’s March, north of Fort Sphinxmoth Wayshrine, norther Fort Sphinxmoth.
Inside Fardir’s Folly solo dungeon. You can approach and enter the dungeon from its southern side. There is a small dirt path leading to it from Fort Sphinxmoth Wayshrine.
The shard you are out for is inside the largest central room. It can be found in the corner of the upper platform of this room. This part is designed to be approached by climbing the wooden bridge from the room in the southwestern part of the dungeon. You can, however, jump toward the shard from the top of the first stairs you find as you enter the dungeon, but this requires a bit of skill and patience.