Treasures can be opened to find cosmetic items or sets. Treasures are obtained through the item drop system, or bought directly from the Dota 2 Store. Each treasure can be opened once, and can contain a few different items. Starting with 85 - Treasure of the Rotted Gallows, Treasure contents cannot be traded or marketed for three months after the release of the Treasure. This does not apply to Extremely Rare drops.
Each treasure comes with a list of Standard drops, as well as Very Rare drop(s). Some treasures also contain Extremely Rare drop(s), often an Unusual courier, which occur at approximately 1-2% chance. Item rarity does affect drop chances.
Opening several of the same treasure will guarantee a different item will be received each time. This rule does not apply to Very Rare or Extremely Rare drops. After all standard items have been received, future treasure openings will yield random items from the droplist.
Some treasures, such as 37 - Ancient Scroll Case, always drop multiple items.
Treasures, previously known as Treasure chests, required a Treasure Key to unlock. Treasure chests were a common drop from the item drop system, while keys could only be purchased from the Dota 2 Store. On June 06, 2014, all Treasure chests requiring specific keys were removed from the game, and on August 14, 2014, all remaining Treasure chests changed in this way. On these dates, chest-specific Treasure Keys were converted into treasures that needed no key to open, and regular Treasure Keys could be redeemed for any unlocked Treasure, and were set to expire on July 1, 2015.