Here's how to get there:
1. Complete the previous seven gyms: You need to defeat all seven gym leaders in order to challenge the Pokémon League.
2. Obtain the National Dex: After defeating the Elite Four and becoming Champion, speak to Professor Rowan at the Pokémon Center in Snowpoint City to obtain the National Dex. This allows you to catch more Pokémon and trade with other players.
3. Defeat the Elite Four: After entering the Pokémon League, you need to battle the Elite Four: Aaron, Bertha, Flint, and Lucian.
4. Challenge Cynthia: Once you've defeated the Elite Four, you'll face Cynthia, the Champion of Sinnoh. She is a very tough opponent, so make sure your team is well-trained and prepared.
Tips for Battling Cynthia:
* Use a diverse team: Cynthia has a variety of types, including Dragon, Ghost, and Steel. Make sure your team has a good spread of types to cover her weaknesses.
* Prepare for her signature Pokémon: Cynthia uses a Garchomp with the move "Outrage," which can be very dangerous. You can counter it with Electric-type moves, like Thunderbolt.
* Focus on strategy: Don't just throw out your strongest Pokémon. Think about type matchups and choose your moves carefully.
* Take advantage of your abilities: Consider using items like X-Sprays, Max Revives, and Ethers to give your Pokémon an advantage in battle.
Good luck defeating Cynthia and obtaining your eighth badge!