Found inside Gurzag’s Mine solo dungeon. Approach the dungeon from south. Collectible is on top of a tall platform, inside the last and the biggest cave room. This place is guarded by cave boss – Retribution, who gives cave completion achievement once killed. Inside the same room, you can find a backpack. This backpack stands next to a small tent. It gives the quest “Forthor’s Cursed Axe“.
Find and enter Gurzag’s Mine.
Dungeon entrance map location.
The path that leads to the shard was added post-launch.
Exact location of the shard.
Sand Kingdom Moons - Super Mario Odyssey Power Moons