The Shadow Chest is a storage item found only in the Underworld, generally on top of or within Ruined Houses, and contains rare items. All Shadow Chests are initially locked, requiring a Shadow Key to open. A single Shadow Key will open unlimited Shadow Chests (unlike Golden Keys, which are consumed upon use). Each Shadow Chest contains one high-tier item of "Orange" rarity, along with other standard Underground loot.
Like all other naturally-occurring Chests, Shadow Chests can be freed with a Pickaxe or Drill after being emptied, and picked up by the player for placement and use elsewhere.
It contains one rare item and a random but limited amount of common items.