Follow the main road that takes you to this part of the map. As you reach this area head to the westernmost house. This is a burned down house with a stone foundation. Inside this house you can find the shard.
Quest “Special Blend“, step “Find the Thane’s Lair”, takes you to the vicinity of this house. This quest is part of The Everfull Flagon objective. You can accept it from dead Gamirth just in front of the entrance to the main Everfull Flagon building.
Sand Kingdom Moons - Super Mario Odyssey Power Moons