Chapter 12: Kahuna Hapu
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Part 12: Kahuna Hapu
Exit this room to the south to meet up with Lillie. Gladion will give you the Sun Flute (Moon version), or the Moon Flute (Sun version). You'll also get the Master Ball. Head south and take the elevator to the docks on B1F. Head left and speak to Gladion, tell him you're ready to go. You'll arrive at Seafolk Village on Poni Island. Head north a little bit and you'll meet the chief of seafolk; he'll tell you shoud find Hapu's house. You can find a Zygarde Cell on the north-right dock across from the Pokémon Center. Head north of town into Poni Wilds.
After a short cutscene with Lillie, head left and grab the Max Repel and the Zygarde Cell on the beach. If you surf out onto the water you can find a Pearl String and a Dusk Stone by diving. Head north of the beach to find two trainers, some berries under a tree, and a Rare Candy.
Head back south and explore the central area to defeat a trainer and find some more berries under a tree. Head to the right of the berries for a Max Potion. To the right of this you'll find a Zygarde Cell near a slope with another berry tree. Head south and defeat another trainer before leaving the area to the right.
Ancient Poni Path
A cutscene where Hapu tells you that Poni doesn't have a Kahuna will play upon entering Ancient Poni Path. Hapu's grandmother will then register Machamp to your Ride Pager. Grab the Zygarde Cell (daytime only) by the wall to the north. Go through the tall grass below you to find an Adrenaline Orb. Head back north inside the couryard on the right side of the house and grab another Zygarde Cell. From here you'll see a Shiny Stone in an item ball that you can wrap around and grab. Head to the right and south to follow after Hapu and battle two more trainers. Head left and north into the tall grass to grab TM79 - Frost Breath. Continue right towards the Ruins of Hope. You'll find another Zygarde Cell next to the entrance.
Ruins of Hope
Pick up the Zygarde Cell before speaking with Lillie. Enter through the door. Use Machamp to push the stone closest to you all the way forward, then push the stone in the middle to the right. Wrap back around around and push it into the hole in the ground. Enter through the door to the north. A cutsene will reveal Hapu as the new Kahuna of Poni. Exit the Ruins of Hope and fly back to Seafolk Village and a cutscene will immediately begin. Heal up if you need, and then head to the dock south and to the left. The chief of seafolk will take you to Exeggutor Island once you're ready.
As soon as you get on the island, you'll have to face off against an Alolan Exeggutor. Head north towards Lillie and it will start to rain. She'll tell you about a memory with her mother during a cutscene. Head to the right side of the spiral path to find a Prism Scale. Head up the sprial to gain elevation and investigate the bush to the north for a Heart Scale. Speak with Lillie and you'll get the Moon Flute (Moon version) or the Sun Flute (Sun version). You'll then take the S.S. Magikarp back to Poni Island.
Once back on the island, make your way back to Hapu's house on Ancient Poni Path just as you did before. Head north where you'll find Lillie and a slew of Team Skull grunts. You'll have to defeat two grunts (6 total Pokémon) and then Plumeria will show up to break up the fight. She'll express concern for Guzma and give you Poisonium Z.
Pick up the Zygarde Cell to the right and then head north into the next area. Speak to Hapu and she'll challenge you to a battle: this is your Grand Trial. She specializes in Ground type Pokemon and has a Lv. 47 Alolan Dugtrio, a Lv. 47 Flygon, a Lv. 48 Mudsdale, and a Lv. 47 Gastrodon. A strong Ice, Grass, or Water type will work well for you in this battle. When you win, she'll give you Groundium Z. Your Grand Trial of Poni Island will be complete.