Bone Mask

Bone Mask is a clothing item that can be obtained as a random reward from a Mystery Bag sold at the Night Merchant's Tent. It is available late on the 19th of each season, starting in year 2.

Because it is tied to the Mystery Bag rotation, there is no direct purchase method for Bone Mask itself; players have to buy the bag and rely on the random contents. If you are looking for it, the key thing is to check the Night Merchant on the correct date rather than waiting for a standard shop inventory.