The "heavens pipe" or "Azure Flute" can be obtained by either a Pokemon event or an action replay
go to were the shamen is
srry u have to go to a Nintendo event 4 it
I'm not sure
Nintendo Event
get heavens pipe go to spear pillar n stairs will appear walk to the Pokemon n battle him on level 80 Event-only, brah. Sadtimes to be sure.
You have to go to a certain Nintendo event to get one.
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Once you have got heavens pipe, go to where you battled palkia or dialga. Go to the symbol beetween the pillars and use the heavens pipe and some stairs will appear. walk up these stairs and you will be at the battle dimension. You wiil find an arceus lvl 80.
Action replay or Nintendo event. I used action replay because Nintendo doesn't give them out often.
Arceus can only be obtained in an "event" that has yet to be scheduled in the us.
you get it from a special event that Nintendo hosts .