After you discover Misko's treasure in the Coliseum Ruins Cave, you get a clue to the next treasure.

Quest Location

Read the stone tablet in the Coliseum Ruins Cave to start this quest.

How to Complete the Quest

It is helpful to have a stake capsule for this quest. One of the places to get stakes is the device dispenser next to Digdogg Suspension Bridge, south of Outskirt Stable.

The clue for this quest is referring to the Thundra Plateau, southwest of Lindor's Brow Skyview Tower.

At the Thundra Plateau, you find a trap door. To open it, you need to cast a shadow from the southern column to the northern column at noon, and this needs to be done in sunny weather, so it might be helpful to have wood and flint, as well as a way to shield a campfire from rain.

If you are ready, go to the south end of the plateau and use a sharp weapon to cut down at least two mushroom trees. Attach them end-to-end, then attach a stake to one end of it, and put the stake into the southern column. Move the stake as far up as it will go, then climb up the column and pull the tree trunks upward so you can put the stake into the top of the column. At noon during sunny weather, the shadow that they cast will reach the shadow of the northern column. If you don't have a stake, you can cut down all six trees on the plateau, connect them all end-to-end, and use Ultrahand to hold them up against the the south side of the southern column at noon. Make sure to hold them as far up in the air as possible.

If you did it correctly, the trap door will open. Go in to find the Thundra Plateau Cave, where you will find one of Misko's treasures.