Walkthrough: After defeating Plumeria and getting to the end of Akala Outskirts, you will arrive at the Ruins of Life. Directly outside of them is where you will battle Kahuna Olivia, the woman you met right after arriving on Akala Island. Lillie and Burnet will arrive before the battle begins, with Lillie actually watching the battle itself. Olivia is a Rock Type Pokemon User, one that can use the power of Z-Crystals
Kahuna Olivia - Level 27 Anorith, Level 27 Lileep, Level 28 Lycanroc
After defeating her, you will earn the next Stamp on your Passport that will cause all Pokemon up to Level 50 to obey you. Olivia will also give you Rockium Z. After the battle ends, Hau will quickly come on the scene and challenge Olivia to his Grand Trial. As Hau battles her and Lillie continues to watch for his sake, you will head to the Hano Grand Resort to meet with the Aether Employee you met earlier.
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