That stone is where you would meet Professor Oak when you receive the Nintendo Event for Oak's Letter. There, you are able to catch Shaymin. What gets engraved on the stone is what you are most thankful to. Here's the event code. Get the letter from the green guy in any Pokémart.
Shaymin Event for Diamond and Pearl (L+R)
94000130 fcff0000
b21c4d28 00000000
b0000004 00000000
0000aa3c edb88320
2000aa68 00000009
d2000000 00000000
Shaymin Event for Platinum (L+R)
94000130 fcff0000
62101d40 00000000
b2101d40 00000000
0000b5d4 00000009
0000b5d8 00000000
d2000000 00000000
Note: US codes
He goes to Route 224...
You can't access Route 224 until professor Oak upgrades your Pokemon. Then go east of Victory Road. Route 224 is the eastmost Route in Diamond Pearl and Platinum.
After you gain Oak's letter you can go to route 224 and catch shaymin
Route 224 You need to use the pokeradar Theres a 2% chance of finding one
First, go to the Pokemon Leauge.Then, right above the Pokemon League is route 224
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You find Shuckle on Route 224 after you get the National Dex and you have Pokemon Emerald inserted in Slot 2 on the DS.
After you have beaten the Elite 4 and Champion, you can access Route 224. If you enter Victory Road from the northern entrance by the Pokémon League, you will be able to get to a cave that was previously blocked by a man. Go into that cave and through it, and you will emerge on Route 224.
A silver rock
The pokeradar!
you get shuckle on route 224
on route 224 Edit: But Dawns lil Sister has to say Route 224! They said theres a whole bunch of Natu's There.