Guide:
Central Deshaan, north-northeast of Ghost Snake Vale Wayshrine, west of Lagomere Dolmen.
Inside the Triple Circle Mine solo dungeon. Start at Ghost Snake Vale Wayshrine and go north. Cross a small river and continue until you see a river downhill. You should see waterfalls to your left (west). Head for them following the southern river bank and you will notice wooden doors in the cliff. That’s the entrance to the dungeon. Enter and follow the dungeon path until you reach the north room (it’s a wooden platform). The skyshard is located there, inside a wooden cart, next to wooden doors.