I need help please!! Im in the Arbiter's Grounds, I've already goten all..

Ahh more specific, push the spiral down to different levels to access different rooms, pushing it all the way down gets you to one room, half way to another etc.

In one of the rooms you can find the key, you can get to the rooms by pushing the thingy that turns and stuff... After you got the key you push the thingy agian till you go to the bottom there you will find the locked room

I will clearly explain what you have to do.
When you walk through the door that opens after you kill the four poes you have the choice to go left or right. If you go right you will drown in the quicksand so left. Jump all the way down and go three floors up (turn the key three times clockwise) to find a doorway, unfortunately it is covered in spikes so walk left along the edge for a bit and you will find a passage that leads to a key. Now go down four floors (turn the key four times anticlockwise) to find a doorway with a lock on it. Use the key with the lock and what do you get? An answer to your question.

Zelda_Fan

Fall to the bottom of the spiral room, turn the column counterclockwise twice and go get the Key - now push the column clockwise until you can't anymore and use your Key on the door...