After you beat ran out front of the Dept. Store in White Port, go inside the store and head to the 2nd floor. There is a person in all black who will give you the marble key.
With the secret key which is found in the Pokemon mansion.
revive a pokemon from a fossil and beat the fire gym leader Actually, you need to get the key from the Pokemon Mansion. It wouldn't make sense to require you to beat the gym in order to unlock the gym!
You have to use the Unova Link, and you can use the Infrared connection with someone who has Pokemon Black 2 (which has Black City), and receive the key from them.
You unlock a place where Rotom can change its forms.
That is easy. You have to go to the Pokemon mansion and find the key to unlock the gym.
You have to go into Pokemon mansion. Find the key in the basement.
With the Galactic key you can unlock any locked doors in the headquarters.
With the secret key which is found in the Pokemon mansion.
ask google
The key is in the Pokemon mansion.
With the secret key.
You can find the key to unlock the door in Pokemon mansion
The basement.
You have to find the key in the abandoned mansion.
use the basement key in goldenrod city. the key is in goldenrod.
Find the secret key in the Pokemon Mansion,( Next to the gym)
you go to the Pokemon mansion next to it and at the very end of it is the key to the gym