Diamond Keys are a new addition to Borderlands 3. While the well-know Golden Keys give you access to nice loot in a golden chest, Diamond Keys give you access to an entire room of loot. The first thing players need to do is buy the Directors Cut DLC. Unlike new systems like Maurice's Black Market, Diamond Keys are part of the DLC only. The Director's Cut will give players access to the Vault Cards, a new mechanic. Vault Cards can be leveled up by just playing the game, finishing quests, and killing enemies. The Vault Cards will give a new reward each time they are leveled up, in the form of a Vault Card Crate. These crates can contain all manner of rewards, including Diamond Keys. These are extremely rare drops, so don't expect to have too many of them come your way. How to Use the Diamond Key Once you have gotten lucky and received a Diamond Key reward, you can use it to open the Diamond Armory. This can be found under the bridge of Sanctuary 3. In the center of the room is a plinth with a diamond symbol on it, and when a key is inserted the player will get access to all manner of rewards. Multiple rewards will appear on each wall, and players get to choose one from each group to add to their collection. This will need to be done quickly, however, as there is a countdown that dictates how long you get to look at the loot.