When you have completed the Island Trials on the island, you'll then be able to face the island Kahuna. This is the closest thing to Gym Battles. Completion of the Grand Trials come with benefits

Grand Trial #1: Hala

Specialty: Fighting-type

Details:
After completing Ilmia's challenge, when you return to Iki Town, Hala will challenge you to a battle. Defeat him and you'll get the stamp for your Trainer Passport which allows traded Pokémon up to Level 35 to obey, the Fightingium Z Crystal and he will give you access to the Rider Pager.

Island Kahuna Hala MankeyMakuhitaCrabrawler
Battle Type

Items
Level 14Level 14Level 15



Attacks:
Karate Chop
Pursuit
Focus Energy
Attacks:
Arm Thrust
Sand Attack
Fake Out
Attacks:
Pursuit
Power-Up Punch
Leer
Hold Item:
No Item
Hold Item:
No Item
Hold Item:

Fightinium Z
Grand Trial #2: Olivia

Specialty: Rock-type

Details:
After completing the three Island Trials on Akala Island, Lillie will ask for you to take her to the Ruins of Hope. When there, Olivia will challenge you to the battle for the Grand Trial. Defeat her and you'll get the stamp for your Trainer Passport which allows traded Pokémon up to Level 50 to obey, and the Rockium Z Crystal.

Island Kahuna Olivia NosepassBoldoreLycanroc
Battle Type

Items
Level 26Level 26Level 27



Attacks:
Rock Slide
Spark
Thunder Wave
Attacks:
Rock Blast
Mud-Slap
Headbutt
Attacks:
Bite
Rock Throw

Hold Item:
No Item
Hold Item:
No Item
Hold Item:

Rockium Z
Grand Trial #3: Nanu

Specialty: Dark-type

Details:
After completing the two Island Trials on Ula'ula Island, and facing off against Team Skull in Po Town, then Nanu will introduce himself after helping you briefly. As Lillie gets kidnapped and you, Gladion & Hau head to the Aether Foundation to rescue her, Nanu will inform you that he is the Kahuna of Ula'ula island and challenge you to a battle. Defeat him and you will receive the Darkium Z Crystal and the Trainer Passport stamp that allows for Pokémon up to Level 65 to obey.

Island Kahuna Nanu SableyeKrokorokPersian
Battle Type

Items
Level 38Level 38Level 39



Attacks:
Power Gem
Shadow Ball
Fake Out
Attacks:
Crunch
Assurance
Swagger
Earthquake
Attacks:
Power Gem
Fake Out
Dark Pulse
Hold Item:
No Item
Hold Item:
No Item
Hold Item:

Darkinium Z
Grand Trial #4: Hapu

Specialty: Ground-type

Details:
The final Grand Trial is done a bit differently. When you reach Poni Island, you will discover that there is no Kahuna on the island. The previous one, Hapu's grandfather, passed recently and Tapu Fini has yet to choose a successor. However, as you need to the Kahuna's help, Hapu goes to the Ruins of Hope to request a Kahuna be chosen and becomes the Kahuna. She finally battles you in front of Vast Poni Canyon.

Island Kahuna Hapu DugtrioGastrodonFlygonMudsdale
Battle Type

Items
Level 47Level 47Level 47Level 48




Attacks:
Iron Head
Earthquake
Sucker Punch
Sandstorm
Attacks:
Muddy Water
Mud Bomb
Recover
Attacks:
Earth Power
Dragon Breath

Attacks:
Heavy Slam
Earthquake
Double Kick
Counter
Hold Item:
No Item
Hold Item:
No Item
Hold Item:
No Item
Hold Item:

Groundium Z