After defeating Guzma at Po Town, return to the Aether House on Route 15. Just when you solved one problem, another–far bigger–problem pops up. Before you have time to properly digest the situation, Gladion comes running in, and uses your Pokémon party as a means to relieve his stress.
Team Skull Gladion
The boy with the aching hand is back. His first Pokémon, Golbat, is weak to Electric, Rock, Ice and Psychic. It can use Acrobatics to inflict heavy Flying-type damage, Poison Fang to potentially inflict poison, and Venoshock to badly damage poisoned Pokémon.
Next up may be Zoroark, but disguised as Type: Null. An easy way to tell is by looking at its Level–if it’s 42, it’s Zoroark. Anyway, Zoroark has Night Daze for STAB damage, Hyper Voice for those that resist Dark, and Grass Knot to punish heavier Pokémon.
Zoroark is also holding Darkium Z, so a Pokémon that resists Dark is recommended. Fairy and Fighting satisfy this condition, while being super-effective. Just be careful as Zoroark is quite speedy and can hit hard with Hyper Voice. Thankfully it’s really frail.
Finally, Gladion’s best friend, Type: Null has Crush Claw for STAB damage, Pursuit to punish Ghosts or those attempting to switch out, and X-Scissor just because. Although Type: Null is still strong, you ought to have fully evolved Pokémon that match or surpass its stats.
Once Gladion has calmed down, he’ll request your assistance to infiltrate the headquarters of the true villains working behind the scenes. You can either allow Gladion to take you straight to Malie City’s ferry terminal, or you can head there yourself later, after tying up any loose ends.
When you arrive outside the ferry terminal in Malie City, ready to leave the island with Gladion, you’ll receive an unexpected visit from Nanu. Since you’ve completed all of Ula’ula Island’s trials, all that remains is the Grand Trial. Although it’s rather sudden, Nanu is here to make sure that you leave without regrets.
Island Kahuna Nanu
Nanu is a masterful user of Dark-type Pokémon, so Fighting, Bug and/or Fairy-types should definitely be included in your squad. For safe measure, you should hand out Fightium Z and the recently obtained Buginium Z to your strongest Pokémon, if applicable.
His first Pokémon, Sableye, is only weak to Fairy, which limits your options. Thankfully, this jewel-loving ghost isn’t particularly tough, so even neutral Pokémon should do fine. One possible trick is have Machamp or Lopunny, etc. use Foresight so they can hit Sableye with their super-effective Fighting moves.
Anyway, watch out for Sableye’s Fake Out, which goes first and causes a guaranteed flinch, but only during the first turn Sableye is out. After that initial shock, Sableye will use Shadow Ball for STAB damage or the Rock-type Power Gem if your Pokémon is immune to Shadow Ball or vulnerable to Rock.
Next up can be Krokorok, which is weak to Water, Grass, Ice, Bug, Fighting and Fairy. That’s certainly a lot to choose from! It has the Intimidate Ability, which lowers Attack. For moves, it can use Earthquake or Crunch/Assurance for STAB damage, or Swagger to increase your Pokémon’s Attack and cause confusion.
Finally, Nanu’s Alolan Persian has two naughty tricks up its sleeves. Like the other kahunas’ final Pokémon, it’s holding a Z-Crystal, specifically the Dark-type one. So a Pokémon that resists Dark–namely Fighting and Fairy–is strongly recommended. Otherwise a special tank can probably survive the Z-Move.
In addition, this Persian has the Fur Coat Ability, which halves the damage of physical moves. So if using a Fighting-type, you’ll effectively do neutral damage, unless you’re using a rare special-based move. For attacks, it has Fake Out and Power Gem, just like Sableye, and Dark Pulse for STAB damage and causing flinch.
Disperse Nanu’s darkness and you’ll earn the Darkium Z. That’s three out of four Grand Trials complete now. Having reached this lofty milestone, all Pokémon up to Level 65 will obey you, including those obtained via trades. Your team will also be fully healed for the upcoming task ahead, saving you a trek to the PMC.