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.
Team Galactic Grunt might not be at the end of the mission when you have completed all missions of Pokemon Diamond because you have not beaten the Spear Pillar area where you catch Dialga.
Looker eventually gives you one
In Veilstone City the Galactic Storage has a has two poke balls. In the first room one is the HM02 move, fly.
The storage key is used to open the locked door in the small warehouse in Veilstone city where you can get the HM02 Fly (that's in the warehouse after getting the professor's assistant's pokedex back, you don't need the key for it). After unlocking the door you go down the stairs and battle a bunch of galactic grunts, and later you can find the galactic key and open the locked door in the galactic main building (it's the building that the first grunt dropped the storage key in front of earlier). After going down the stairs there and battling more grunts, if you defeat Saturn you can save the lake guardians (that's Uxie, Azelf, and Mesprit). Hope this helps!!
It walks away and leaves it behind the galactic building after you talk to him.
Head back to Veilstone City. When you arrive at Veilstone City, make your way to the Galactic HQ and talk to the Grunt standing next to the satellite dish. He'll drop the Storage Key before running off. Pick up the key, and head to the Galactic Warehouse to unlock the rusty door. You'll now be in the inside the Galactic HQ.
you use it in the galactic building in veilstone city, but only on certain doors
In Veilstone City the Galactic Storage has a has two poke balls. In the first room one is the HM fly.
In the team galactic storage house connected to veilstone galactic headquarters.
in the storage place in veilstone is the galactic key, u just gotta find it.
Looker eventually gives you one
You find it in the team galactic storage area.
You have to go to Veilstone City to the headquarters of Team Galactic. and the man before the headquarters has the Storage Key. with this key you have to go to the Warehouse (at the top on the left side), also in Veilstone City.
It opens the door to Cyrus the main boss of team galactic. Be prepared because after him you must defeat either Mars or Jupiter, they are very strong at that stage.
You speak to the galactic guy out of the HQ .. he leaves and drops a pokeball in which is the storage key...Go and use it in their storage ( same town somewhere near the top left of the city ).. I think the key to the HQ is somewhere in there..:) By Nekt;)
u catch girantina and then after that you go to veilstone city and go talk to the team galactic person in front of the galactic warehouse I think galactic warehouse it is one on the team galactic places in veilstone city and then he will go somewhere and drop a key which it will be the storage key. Hope this helped and sorry I cant think of the name of the team galactic place it is the biggest building of the team galactic places (in veilstone city)
The Storage Key opens the Galactic Warehouse in Veilstone City. It is dropped by a Galactic Grunt in Veilstone City after you beat Jupiter at lake Acuity.
if you past the 7th gym then go back to veilstone city then go right and the go up then you se a guy next to the galactic Veilstone building then he drop his storage key.