The Treasure Chest is a loot drop that often has very high tier loot. Currently in the game there is 1 Treasure Chest. Opening the Chest however will require player level 80. The first Treasure Chest is at the inlet at viking bay. You will find the Chest in a sunken pirate ship (22.1 33.2) the Chest is inside the ship. However you cant just mosey on in there and grab it as it is guarded by around 30 Eurypterid. A high level sea creature is recommended but a Baryonyx can do.