You can encounter more Legendary Pokémon in Pokémon Brilliant Diamond and Brilliant Pearl. Many of these Pokémon weren't in the original Diamond and Pearl games, giving you the ability to fight in new encounters and earn Legendary Pokémon that you may not have seen in these games. In this guide, we will detail how to find Rayquaza in Pokémon Brilliant Diamond and Brilliant Pearl.
You can find Rayquaza in the same location you find the other Legendary Pokémon, which is in Ramanas Park. You can reach this building when you complete the game and finish the Sinnoh PokéDex, unlocking the National PokéDex.
Before reaching this point, we recommend that you investigate the Great Dungeon to find mysterious fragments. These are the items you will need to deliver to Ramanas Park, receiving your slates to fight these Legendary Pokémon. You can find mysterious fragments by digging in the fossil mini-game. There are small and large mysterious fragments. These are rare items, so we recommend increasing your Diglett and Dugtrio bonus counter under the map on the left side of the screen from 35 to 40.
You will need to find three small mystery shards or one large mystery shard. When you have them, head back to Ramanas Park and purchase the stratospheric slate. This is what you need to summon Rayquaza. You can find Rayquaza in both Pokémon Shining Diamond and Shining Pearl.