How do you catch Arkias in Pokemon Diamond?

Answer 1

First, you must obtain the Azure Flute. (Only obtainable though and event or GameShark) Once you obtain the Azure flute, go to the Hall of Origin on Mountain Coronet (Where you catch Dialga and Palkia). When you enter the Hall of Origin, it will ask you if you want to play the Azure flute. Say yes and it will play a little tune. After that, a staircase will appear; walk up it until you see a platform. Save right when you get in front of it!

Here is the Action Replay code for the Azure flute:

94000130 FCFF0000 B21C4D28 00000000 B0000004 00000000 0000AA3C EDB88320 2000AA68 0000000A D2000000 00000000 Press L + R and walk into a Pokemon Mart after entering the code above. You will see a guy in a green suit that will gie you the Azure flute.