The Card Key is necessary to drive Team Rocket out of the Goldenrod Radio Tower for good. You can get this Key Item from the Radio Director who’s being held prisoner at the Warehouse in the Goldenrod Underground.
But to enter the Underground Warehouse you must have the Basement Key, which you’ll get after defeating a Team Rocket Executive at Goldenrod Radio Tower 5F.
Acquiring the Card Key is the second step in liberating Goldenrod Radio Tower from Team Rocket.
First, you need to visit the Radio Tower’s fifth floor and defeat the Team Rocket Executive who’s been impersonating the Radio Director. After that battle you’ll receive the Basement Key needed to enter the Underground Warehouse.
Getting the Card Key
Once you have the Basement Key then you’ll be good to go chase after the Card Key.
Here’s what to do:
Step 1: Find Team Rocket’s Underground Warehouse
Once you have the Basement Key we’ll need to head for the Goldenrod Underground.
Starting at Goldenrod’s Pokémon Center just head north.
Cross the train tracks, then turn left, and enter the second building.
Inside, you’ll find some stairs heading down into the Goldenrod Underground.
Go down the stairs and start going south, then turn east at the earliest opportunity.
The door to the Underground Warehouse is at the end of the road. Use the Basement Key to open it and head inside.
Note: You might have to fight some trainers if you’ve never been here, but their Pokémon are all very low-level. They shouldn’t be a problem at this point in the game.
Step 2: Press the Switches in Order to Open the Way Forward
You’ll bump into your rival shortly after entering this area.
He has five Pokémon in the Lv.28-32 range in his team, so be prepared!
Once that’s done, keep going left to the other side of the room.
Tip: Remember you can always head back to the Pokémon Center to heal before continuing.
You’ll have to battle three Team Rocket Grunts with Normal and Poison-type Pokémon on the way, but they shouldn’t be a problem compared to your rival.
There are three switches along the northern wall in this room. Press them in order from left to right to open the way forward.
Tip: If you’ve already moved the switches around, you can exit the room and re-enter to reset the switch positions.
Once you’ve pressed the switches in the exact order above, the doors below you should now lead to the room with the Director.
From the top left corner of the room, head down, then right. Watch out for Burglar Eddie and his two Pokémon.
Then go down and right once again.
Burglar Duncan has one more Pokémon than Eddie, but his party is still nothing to worry about.
Finally, head all the way to the right. Defeat the Rocket Grunt here and then enter the gate behind her.
Tip: There’s a Full Heal on the ground to the north before the Rocket Grunt.
Step 3: Rescue the Radio Director
Once you go through the double doors you’ll just need to follow a pretty straightforward path to find the Radio Director.
Expect plenty of combat along the way!
Start by heading north from the entrance.
Follow the hallway as it bends right and then back down.
There’s also an Ultra Ball in the top left corner of the U-Turn. Doesn’t hurt to pick it up!
Keep following the path as it turns right, and you can pick up the Max Ether next to some crates in the corner.
As you head up the hallway you’ll soon see a staircase guarded by a Rocket Grunt. There’s an Amulet Coin up the stairs, so consider checking it out before continuing.
But you can also skip the staircase and just head down the western hallway if you just want the Card Key.
Finally you’ll fight past one last Rocket Grunt and reach the center of the warehouse where the Radio Director is being held.
Tip: Make sure to pick up the nearby item on the ground – it contains TM35 Sleep Talk!
Talk to the Radio Director to release him.
He’ll then give you the Card Key to help you reach the remaining Team Rocket executives in the Goldenrod Radio Tower.
What Does the Card Key Open?
The Card Key will allow you to enter a sealed-off area of the Goldenrod Radio Tower where the last remaining Team Rocket Execs are hiding.
Just use the Card Key to open the security gate on the third floor (3F), then go up the stairs to the fifth floor through the newly revealed stairs to reach them.