There are several evolutionary items you’ll need to find to evolve your Pokémon. The Thunder Stone is one of many evolution items. You can use it to evolve Magnezone. There’s only one Thunder Stone to be found in the base game overworld. This walkthrough will show you where to look for a Thunder Stone in Pokémon Brilliant Diamond and Shining Pearl.
- The Thunder Stone can be found behind the Vista Lighthouse in Sunyshore City. Follow the raised bridges to the right until you reach a staircase. Go to the bottom of a long staircase, where you’ll find the item Pokeball.
- After defeating the Elite Four, you’ll be able to find another on Route 229, just north of the Resort Area.
- Thunder Stones can be obtained by digging out the bulging walls found in the Grand Underground.