After passing through Route 10 and defeating some Team Skull Grunts, you take the bus to the top of Mount Hokulani.
Explore Mount Hokulani
At the top, Professor Kukui shows you the peak of Mount Lanakila and tells you his plans to create a Pokémon League there where people can battle the Island Kahunas as the Elite Four.
After the cut scene, go southeast of the Pokémon Center and talk to the guy there to get a Moon Ball.
Northeast of the Pokémon Center, you find a Level Ball.
You can go down the mountain road to battle trainers if you wish.
The first trainer that you encounter if you go down the mountain road is Office Worker Jessica. She has a level 28 Clefairy. You get 1120 Pokédollars for winning.
Farther down the mountain, there is a slope above you. Go down it, then go east through the grass to find TM72 Volt Switch.
Go farther down, and you will find a Fast Ball on the left.
South of that, you can find a hidden Rare Candy on the right.
Farther down, you can battle Hiker Thomas. He has a level 27 Boldore and a level 28 Geodude. You get 896 Pokédollars for winning.
South of the Hiker, there is a ramp to the left. Go down to the grass, then go north to find a Heavy Ball.
Go north to the edge of this ledge to find a Poké Finder spot.
On the south end of this ledge, you can battle Collector Todd. He has a level 28 Passimian and a level 28 Oranguru. You get 896 Pokédollars for winning.
South of the Collector, there is a one-way ledge. Go down the ledge, then go south through the grass to find a Max Potion.
That is all to be found on the Mount Hokulani road, so use the Ride Pager to go back up to the Mount Hokulani Pokémon Center.
From there, go north to the Hokulani Observatory. You will meet Molayne at the door. He will battle you to test if you are ready for Captain Sophocles's trial.
Pokémon Trainer Molayne has a level 29 Skarmory, a level 30 Dugtrio, and a level 29 Metang. You get 3000 Pokédollars for winning.
After the battle, go into the observatory and talk to the guy behind the counter on the left to get a Comet Shard.
Go through the doors in the back.
In the far left of this hallway, there is a green sparkle for the Zygarde Cube.
Go to the middle of this hallway and go up through the colorful door.
Go up into the room to meet Sophocles. He will start the trial right away.
After a cut scene, you are given an audio quiz. You have to recognize the sound that was played. Click the button for the correct answer to the first sound:
After this, you have to battle a level 27 Grubbin.
After the battle, and a cut scene, there is another audio quiz. Click the button for the correct answer to the second sound:
After this, you have to battle a level 27 Charjabug.
After the battle, and another cut scene, there is another audio quiz. Click the button for the correct answer to the third sound:
After this, you have to battle another level 27 Charjabug.
After the battle, and yet another cut scene, there is another audio quiz. Click the button for the correct answer to the fourth sound:
After this, you must battle the level 29 Totem Vikavolt. It can call for help from Charjabug.
Afterward, Sophocles gives you Electrium Z, and Molayne gives you Steelium Z. He also gives you the Professor's Mask and asks you to take it to the Professor, who went back to Malie Garden.
At Malie Garden, you find Professor Kukui dealing with some Team Skull Grunts. Kukui challenges them to a Battle Royal. Then the boss of Team Skull, Guzma, arrives. You have to battle him.
Team Skull Boss Guzma has a level 31 Golisopod and a level 30 Ariados. Golisopod has the ability Emergency Exit, which allows it to switch out when its HP is 50% or lower. You get 3600 Pokédollars for winning.
Afterward, Kukui gives you a Z-Crystal for your starter pokémon.
Acerola tells you to go through Route 11 on your way to the next trial.