you can't get origin form in diamond and pearl, but in platinum you can
Chat with our AI personalities
you cant only platinum unless an action replay code
The "Griseous-Orb" is found in "TurnBack-Cave". It is item to be held by Giritina. It powers up ghost and dragon type moves and turns giritina into origin form(e).
After you go and beat the elite 4, make your way to spring path. you will find the Griseous orb. give it to Giritina and he will change forms.
ghost/dragon
There is a new Pokemon game coming out soon, which is called 'Pokemon Platinum', the sequel to Pokemon Diamond and Pokemon Pearl. Giritina is in its reverse world form, shaymin is in its sky form, and there is an entirely new plot in Pokemon Platinum.