Inside Tribulation Crypt solo dungeon. Entrance into the dungeon is north of Sanguine Barrows and its wayshrine and is marked on the big map. Exact location of the collectible inside the dungeon is shown on the screenshot bellow.
Tribulation Crypt entrance (as marked on the interactive map)
You do not have to go too far inside the dungeon to pick up the shard. It is in the first small room you come across.
Map of Tribulation Crypt showing the exact location.