After you complete the three trials at the lakes, your next mission is to reach the top of Mount Coronet.

Go to the Front Gate

Go to the Front Gate of Jubilife Village. You will receive a Max Revive and 3 Max Potions.

Go to Stone Portal

Go to the guidance marker east of Summit Camp in Coronet Highlands. Make your way through the cave and there will be a cutscene.

Do Battle

You will have to battle Mismagius, Sneasler, Gardevoir, and Gallade.

Your pokémon will be healed after the battle.

Go Up the Mountain

Go up the slope and leave the cave. Go up the slope, and you can talk to Volo to purchase items. Then approach Adaman and Irida. Go farther up the slope and approach Kamado.

Do Battle Again

You must battle Braviary, Golem, Snorlax, and Clefable.

Your pokémon will be healed after the battle.

Go to the Temple

Go up the slope to reach the temple. In the temple, approach the stairs at the end. You will get 10 Ultra Balls.

Do Battle Once More

You will battle a level 65 legendary pokémon. You can defeat it or try to catch it.

Then begins the next mission, The Counterpart. You will get 3 Candy Truffles.