The Galatic Key is needed to open the doors throughout the Galatic HQ Warehouse and the Galatic HQ in Veilstone City. Without it, you can’t take down the infamous Team Galactic. This key, however, can be a bit tricky to find. Here is where you can find the Galactic Key in Pokémon Brilliant Diamond and Shining Pearl.
Before you can access the Galactic HQ Warehouse, you first need to get the Storage Key by talking to the Team Galactic guard in front of the Galactic HQ in Veilstone City. Head to the northeastern corner to find him. He will drop the Storage Key. Now head back to the warehouse, open the previously locked door, and head down the stairs.
Once downstairs, follow the hallway to the right. You will fight a few Team Galatic Grunts along your way. Keep following the hallway until you find a set of stairs. These stairs will take you to a small room with another set of stairs. Climb those as well. In the next room, you will face off against one grunt and then make the choice of the left warp pad or the right warp pad. Take the warp pad on the left.
In the next room, take the only other warp pad in the bottom right-hand corner. This will lead to another room with a set of stairs. Take the stairs up. After taking the stairs, you will have another choice between taking another flight of stairs up or a warp pad to the left. Take the warp pad and go down the stairs in the next room. You should end up in a room with a scientist. After dealing with the scientist, take the stairs behind him down.
Deal with the final Team Galactic Grunt at the end of the hallway in the warehouse room with the boxes. On the other side of the boxes, you will find the key.
