From Dota 2 Wiki
Treasures are purchasable boxes that contain cosmetic items. They are obtained through the Dota 2 Store, charms, or the item drop system. Each treasure can be opened once to receive one or more random items from its listed contents.
- Each treasure comes with a drop list, categorized into rarity tiers.
- Items in higher rarity tiers are unboxed less frequently.
- An item's innate rarity does not affect drop chances.
- Unusual quality couriers can be unboxed from some treasures at approximately 1-2% chance.
- Chinese servers disclose an official drop rate of 6% for Rare items, and 2% for Very Rare items. These percentages may not apply to all treasures, or on non-Chinese servers.
- Opening multiple copies of the same treasure guarantees a different item is unboxed every time.
- Previously received items will not be unboxed again unless all items have been unboxed.
- This rule does not apply to Rare, Very Rare or Extremely Rare drops.
- After all standard items have been received, future treasure openings will yield random items from the droplist.
- Items unboxed from treasures cannot be traded or marketed for 1 week
- However, restricted items can be gifted once to a friend.
- This restriction does not apply to Extremely Rare drops.