Where can you find Arceus in Pokemon Diamond?

Answer 1

You should have obtained the mystery gift and the National Dex if you want to do this. You need to find a person in the Pokémart in Pastoria City and he gives you a type of flute, and you go to where you caught Palkia (Pearl) or Dialga(Diamond). You get in your inventory and take the Flute out and it asks you to play it, you select Yes and after you play it, there is a staircase leading up to a Hall, and then once you climb up, you cannot save it, so save it before you climb up the stairs, then you see a "!" above your head, you RUSH to the Pokémon and battle it. Hope that helped. :) Arceus will be lvl 70 his ability is multitype

Hey, I think I know what this person is talking about, I did it on pearl but I had action replay so I just the code and followed directions online. I heard that you could go to a Nintendo event and get it (I have no idea what a Nintendo event is) without cheating but I really don't know how without cheating or going to a Nintendo event.

Note:The one below did not work for me, all I found was some misty place and i remember it saying turn back cave several times in the corner.

I heard that if you battled the elite four up to the champion's door, then used a action replay, walk through walls cheat, then went around the door and kept walking forward, you would come to the hall of origin where arceus is.