Found in western Craglorn inside Buried Sands dungeon.
You can approach and enter Buried Sands from east. When you enter the dungeon it soon becomes clear from where this shard got its lorebook hinte. There are only a couple groups of mobs between the entrance and the shard. They are rather large though and this makes them hard to solo. Shard is at the northernmost part of the cave. You can find the final boss just south of it.
Find and enter Buried Sands.
Buried Sands Entrance Map Location.
Shard is just above the final dungeon boss.
Buried Sands Shard Map Location.
Sand Kingdom Moons - Super Mario Odyssey Power Moons