Every area in Tarisland has multiple chests you can find and open for some rewards. Most of these chests are sealed and require you to find or do something to open them.
The sealed chest behind the stone pillar in Luen Spring in Misty Forest requires you to bring a Luna Stone to open it. Since the game doesn’t tell you anything about this item, here’s how to get a Luna Stone in Tarisland.
How to find a Luna Stone and open the chest in Tarisland
Unlike the crystal chests, you can’t simply buy the item you need from the Trade Center. To get the Luna Stone in Tarisland, you need to complete a short side activity. On the world map, find the pink plants southeast of the Luen Spring waypoint (coordinates: 389,857).
Head to the location and right in front of the plants, there’s a fawn stuck in the trap. Interact with the fawn to remove the trap, and follow it for a bit until you reach the Glowing Sapphire marker. Interact with the marker and you’ll get one Luna Gem (which is the same as Luna Stone).
Keep in mind you should have a free inventory slot for the Luna Gem and any other items you might be using to open chests. You can either clean your inventory or get yourself a bag to increase the capacity.
With the Luna Gem acquired, you can then head back to the chest in Luen Spring and open it using the stone.