Eviolite
This goal requires you to obtain an Eviolite.
It is given to you as a Battle League reward for defeating seven trainers in South Province (Area Five).
Alternatively, the Eviolite is available for purchase at Delibird Presents for ₽50,000 as soon as you have completed the game.
Location
Section titled “Location”The Battle League Rep that gives you this reward is located at the Secluded Beach PokéCenter.