You will face a handful of obstacles as you progress through the main story of Pokémon Brilliant Diamond and Brilliant Pearl. These obstacles will require some smarts to overcome and you will need to use specific items. For those with fog problems, what can be done? Here's what you need to do to get rid of the fog in Pokémon Brilliant Diamond and Brilliant Pearl.
You will need to make sure you visit the Great Marsh in Pastoria City. This location is where you can find the useful skill, Defog, also known as TM 97. When you take this TM for the first time, it becomes an HM that you can use on your Pokétch.
Even if you have TM 97 and HM available on your Pokétch, you will still need to defeat Pastoric City Gym Leader Wake. You will not use HM Defog until you win this battle and get this Gym Badge. Wake is the fourth Gym Leader, so make sure you're ready for this challenge. He mainly uses Water-type Pokémon, so we recommend using Electric or Grass-types to defeat him.
You'll be using Defog to remove foggy areas after beating Wake, so you don't have to worry about using this HM until you receive your fourth gym badge.