Treasure Bags are consumable items obtained in Expert Mode as a reward for defeating bosses. Its contents depend on the boss it comes from. It is opened by either right-clicking it inside the inventory or using it while it is in your hand. In multiplayer, each player that is online at the end of the battle receives one Treasure Bag each. Treasure bags are client-side and will despawn if you exit the world.
Each Treasure Bag contains the boss's usual drops from normal mode, along with at least one Expert Mode-exclusive item (orange-highlighted items below).
All Thorium Boss Bags additionally have a 3.33% chance to contain one random set of developer items.
In addition to the above, all Treasure Bags (excluding the Lunatic Cultist Bag) have a 3.33% chance to contain a random set of developer items, with a 5% chance in Hardmode to obtain Phonic Wings alongside the random set. Obtaining a Treasure Bag in an Expert world, then opening the bag in a Normal world will retain the Treasure Bag's chance to yield developer items.
Pressing the Accessory Ability key will trigger True Strikes, which guarantees critical strikes from throwing weapons but requires a 2 minute recharge time.
Pressing the Abyssal Guard key will place you into an impenetrable shell, granting invulnerability but disallowing use of items and nullifying damage done.
Used to craft the Mjölnir, which throws an image of the legendary weapon, releasing a storm of energized lightning bolts that deal very high True Damage when hitting an enemy.
A magic weapon that summons a volley of three arcane bolts from behind the player, which are launched towards the cursor's position and are affected by gravity.