After defeating all eight Pokemon Gyms and signing up for the Champion Cup, you will have to win two Semi-Final Matches before being able to advance to the Finals Tournament of the Champion Cup. Your first Semi-Finals Match will be against Marnie. As you know from your battles with Marnie leading up to this point, she specializes in using Dark Type Pokemon. In this battle, she will use five different Pokemon, four of which will fully or part Dark Types. Because of this, Marnie is especially weak against Fairy & Fighting Type Pokemon & Attacks.
Additionally, all of Marnie's Pokemon will either be at Level 47, Level 48 or Level 49. Due to this, it would be wise to have all of your Pokemon at Level 50 or higher. The more experienced your Pokemon are, the easier it will be to defeat Marnie. And finally, Marnie will Gigantamax her final Pokemon, which just so happens will be Grimmsnarl. Because of this, it would be especially wise to wait to use your Dynamax until she sends out Grimmsnarl. Also, it would be smart if the Pokemon you Dynamax is either a Fairy Type, Steel Type, or Poison Type, since Marnie's Grimmsnarl will be extremely weak to those type of attacks.
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