Walkthrough: Within Route 6 is Royal Avenue. However, as you approach the entrance, you will see a trainer arguing with a few Team Skull Members who are blocking the entrance. Her name is Hapu, and she asks you to help her defeat them. After do so, you can into Royal Avenue where the Battle Dome is. You will then be prompted to head to the Battle Dome and participate in your first ever Battle Royal Match with none other than Mask Royal, Hau, and Gladion.
Team Skull Grunt - Level 17 Drowzee
Battle Royal Matchup
Masked Royal - Level 19 Rockruff
Team Skull Gladion - Level 19 Type: Null
Pokemon Trainer Hau - Level 19 Brionne, Dartrix or Torracat w/Normalium Z