If you have this item and you'd like to get to Shaymin, you must have the National Dex. With this, a new area will open up in Victory Road near the exit. Go there, and you'll team up with Marley or whatever her name is. Take her to the end you'll find yourself near Route 224. At the very end is a white rock. Professor Oak will be standing by it, and when you talk to him, he'll ask you who you give thanks to. Once you do that, the screen will go white and then Shaymin will appear.

Of course, Shaymin won't stick around and returns to the Flower Paradise at the end of the Seabreak Path. This is a very long path, so it is best to ride your bicycle. It is at the very end and at level 30.

What makes this different is that this Shaymin is able to transform. It's second forme, known as the Sky Forme, can only be obtained with event item. A woman in Floroma Town will give you the Glacidea Flower which will transform Shaymin into its Sky Forme. She will give you this item when you get Shaymin. It has better stats than its Land Forme, but has a x4 weakness to Ice.

This key item can be used to transform an infinite amount of Shaymin into their Sky Forme or into the Land Forme. The item will not work when Shaymin is frozen or if it is night out. Shaymin will revert to its land forme whenever it is put into the PC.