What are Key Items?

Key Items are used to open cases for free. You can tell which case a key opens from the name of the key or by clicking on it.

These items cannot be bought, sold or traded. They can only be used to open their own case for free. They appear at the top of the inventory.

As long as the key is in your inventory, you can open its case for free, but only 1 of that case can be opened with each key. After the case is opened, the key is used up and deleted from the inventory.

To learn how to get keys, read What are Deposit Rewards. Some mission rewards are also keys (What are Missions?).