How do you get the king stone for Pokemon platinum?

You can't actually get a King's Stone in Pokémon Platinum. It's a special item exclusive to Pokémon Black & White and later games.

It's used to evolve certain Pokémon, such as:

* Slowpoke into Slowking (when combined with a King's Rock)

* Elekid into Electivire

* Magby into Magmortar

If you're playing Platinum, you can't evolve these Pokémon in the same way.

Here's how you evolve these Pokémon in Platinum:

* Slowpoke: Trade it to someone with a King's Rock and have them evolve it to Slowking. Then trade it back.

* Elekid: Level it up while it's holding an Electirizer

* Magby: Level it up while it's holding a Magmarizer

Let me know if you have any other questions about Pokémon Platinum!