Diancie is a mythical Pokemon found in the game Pokemon Brick Bronze. You will need the Unown Pokemon "O", "P", "E", and "N" to access the hidden area. Make sure they are in your party. The Unown are found in the Desert Catacombs on Route 11. To get Diancie, you'll have to follow a list of steps. :
- Go to Route 13, you need to enter The Chamber of the Jewel which requires HM8 Rock Climb to access. The door is marked with "Open" in Unown text. Stairs lead to the door as well.
- Click onto the door
- Walk forwards toward Diancie following the path. Once you click Diancie, you will engage in a battle
Make sure to SAVE beforehand and TURN AUTO SAVE OFF. If you lose a battle against Diancie, you cannot re-battle it again unless you encounter one in the wild. However, it has a 1/1000 chance in appearing in the wild, so it's best to get Diancie while you can.