in diamond and pearl it's in the wherehouse next to the gelactic buldind in a town but in platinum you defeat the grunts and give dawn her pokedex then looker will come and fallow him the he will give you the key.
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you use th key in the eterna city galactic biulding between the book case and wall
after you get galactic key go to the HQ with sattilite dish go to the door
after u beat the 7th gym leader go back to veilstone city and get the storage key of the team galactic guy standing outside the big headquarters he drops the key then u go into the warehouse and get the galactic key
You find it in the Galactic Headquarters after they capture Azelf, Uxie, and Mesprit.
To get into the Team Galactic HQ in Pokemon Diamond you will need the storage key the Galactic Grunt leaves behind, and the Dusk Stone. If you can't get the key, it may mean you have not completed a mission.
you use th key in the eterna city galactic biulding between the book case and wall
you have to get the secret key
the galactic key is in somewhere in the game N.M.I
You will need Galactic key and this how to get Galactic key you will need to talk to a Galactic team mate by the Galactic HQ.
Take the Secret Key to the Team Galactic HQ in Eterna City. Go to the back of the wall on the left hand side of the first floor.
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When you go to the team galactic veilstone building there will be a galactic grunt and you talk to him then he'll run away and he accidentally drops a key.
In the galactic warehouse to the left of the Galactic HQ
go to galactic headquarters in veilstone city then you need a galactic key and the storage key to open the door of team galactic's door
you go to the team galactic ware house
its in the galactic ware house in velistone
Eterna. You have to have the Secret Key. Go into the Team Galactic Base, and walk into the top left corner of the room. There is a secret passage here, hit 'A' to activate it.