After you become champion, you are permitted to go northeast from Ancient Poni Path into Poni Grove.
Ancient Poni Path
After you become Champion of Alola, you can go to Poni Grove. First, go to Ancient Poni Path. Once there, go northeast to find Hau and Ms. Wicke. You each get a Big Malasada, and Wicke gives you Type: Null, a gift from Gladion. You also receive all of the memory drives that can change Silvally's type. Type: Null will evolve into Silvally if it levels up with high friendship.
Now you can go north to Poni Grove, which was off-limits before you became Champion.
Ultra Beasts in Poni Grove
During a cutscene, you will get five Beast Balls, and you find out that you can buy more Beast Balls in Aether Paradise. The Ultra Recon Squad asks you to catch the Ultra Beasts in this area. In Ultra Sun, you can catch two Blacephalon, and in Ultra Moon, you can catch two Stakataka. Just wander in the tall grass to find them. You might encounter regular pokémon as well. After you have caught or KOed all the Ultra Beasts in the area, a cutscene will occur, and you will be back in your house.
The next day, Sophocles visits. He takes you to Festival Plaza, where things look a bit different. If you agree to help, you go into the castle. Talk to the Team Rocket Grunts, then talk to Sophocles, and he will make the Battle Agency receptionist reappear. Talk to her, then select Challenge to start.
You have to battle Team Rainbow Rocket Grunt. After you defeat him, Sophocles kicks Team Rainbow Rocket out of Festival Plaza, but he adds the Team Rocket castle to the themes that you can use for your Festival Plaza. He also gives you an Eject Button.
Then, after a cutscene, Episode RR begins.
In Poni Grove, east of the entrance there is a Max Potion.
To the north, you can battle Black Belt Roy. He has a level 56 Mienshao. You get 1792 Pokédollars for winning.
There is an X Sp. Atk to the left of the Black Belt.
To the east, there is a hidden Elixir.
Farther east, you can battle Ace Trainer Jackson. He has a level 56 Huntail, a level 56 Alolan Marowak, and a Braviary. You get 3876 Pokédollars for winning.
Keep going along the path to reach Poni Plains.
Go to the southeast part of the area and you can battle Ace Trainer Angela. She has a level 58 Gorebyss and a level 59 Lurantis. You get 4012 Pokédollars for winning.
Go south from her to find a Carbos.
Then go north past the grass.
There is an Ace Trainer north of where you entered Poni Plains. There is a hidden PP Max on the tree northeast of that Ace Trainer.
To the north, there is a Trainer Tips sign. If you go west from there, you can battle Hiker Ryan. He has a level 57 Aerodactyl. You get 1825 Pokédollars for winning.
Go south from Ryan and go down the one-way ledge, then go west to the berry tree. From there, go south and down the one-way ledge.
Go back to the Trainer Tips sign and go west again. This time, go northwest when the path splits, up a slope to a rocky area. go north until you can't go farther north, then go west and break the boulder with Tauros. Then go south and break the boulder there, then go south and down the one-way ledge to get a Comet Shard.
Go south down the one-way ledges and you will be back where you fought the Hiker. Go east through the grass, then go north to return to the rocky area. This time, go to the west side of the area, then go south down a one-way ledge to find a Power Anklet.
To the south, you can battle Police Officer Sheriff, who has a level 58 Stoutland. You get 2320 Pokédollars for winning.
Go south down the one-way ledges, then go east through the grass, then go north to return to the rocky area once more. This time, go to the northwest corner and enter the cave.
This is Plains Grotto. Go north and check on the pedestal to get Kommonium Z.
Leave the cave and go southeast to the grassy area. From there, go east until you can go northeast. In the northeast area, go north through the grass, then go northwest to enter Poni Meadow. As you go in, there will be a cutscene, and you will battle Pokémon Trainer Dexio. He has a level 60 Espeon, a level 60 Slowking, a level 60 Metagross, a level 60 Alolan Raichu, and a level 60 Alakazam, which he mega-evolves into Mega Alakazam. You get 8400 Pokédollars for winning.
After the battle, Dexio gives you the Key Stone and an Alakazite. If you give the Alakazite to an Alakazam, you can mega-evolve it into Mega Alakazam. It works the same way as Z-Powers, but instead of powering up a move, it powers up the pokémon itself.
Go northwest to enter Poni Meadow.
Before you go farther into Poni Meadow, you might want to buy Timer Balls in Paniola Town and buy some Paralyze Heals or grow some Cheri Berries in Poké Pelago. Then you can fly back here to continue.
Check on sparkles in Poni Meadow to get Purple Nectar.
Go north, then west to a tree. There is a Max Potion to the left of the tree. There is also a Poké Finder spot here.
Go east and there is a fishing spot in the water.
Go farther east, then go north up the slope. At the top of the slope, go south and walk across the branches to find a Power Lens.
Then go back across the tree branches, and go north. When you can't go farther north, go east along some branches, then go east through the grass. You may find Actor Meredith here. If you battle her, she has a level 57 Sensu Style Oricorio. You get 2280 Pokédollars for winning. Afterward, Meredith gives you TM75 Swords Dance.
From there, go east across the branches, then go south to find TM50 Overheat.
Go north through some grass, then west across the branches. To the west, you can go down the one-way ledges to find a Power Herb.
Then go back to where you jumped down the ledges, and go west. There are some branches to the south, so go south across them to find a Max Revive.
Then go north and enter the cave.
Go west and use Mudsdale to go across the rocks. You can either go south or west from the rocks. First, go west, and you can battle Veteran Leticia. She has a level 61 Ribombee and a level 61 Bewear. You get 5368 Pokédollars for winning.
Go west from there to find a Power Weight. There is also a hidden HP Up nearby.
Go east to the rocks and go south this time.
To the southwest, you can battle Backpacker Maria. She has a level 59 Manectric. You get 1416 Pokédollars for winning.
To the right of the Backpacker, use Tauros to break the rocks, then go east to find TM26 Earthquake.
West of the Backpacker, there is a narrow passage. It looks like it is a dead-end, but keep going south and you will find a Terrain Extender, which increases the duration of effects like Electric Terrain if a pokémon holds it.
Go back to the Backpacker and go south. Break the rocks on the left and you can battle Hiker Travis. He has a level 59 Alolan Dugtrio and a level 59 Mudsdale. You get 1888 Pokédollars for winning.
Then go east and enter the cave.
Follow the path into the cave. You will reach a crossroads, with a ramp to the north. Before you go up that ramp, first go southwest, where you find a Light Ball. If you go northwest, you find an Adrenaline Orb. If you go southeast, you find a Toxic Orb. If you go northeast, there is a hidden Big Nugget.
Go back to the crossroads and go north up the ramp. Check on Zygarde and you can battle it and try to catch it. Zygarde is level 60. It is difficult to catch, so it is recommended to use False Swipe to take its HP down to 1, then inflict sleep or freeze on it. Then throw Timer Balls if you have them. You can purchase them in Paniola Town. Zygarde knows Safeguard, Land's Wrath, Dragon Breath, and Glare. Both Dragon Breath and Glare can cause paralysis, so bring plenty of Paralyze Heals and Cheri Berries, or just use an Electric type pokémon since they are immune to Paralysis, or bring a Komala, which is also immune to Paralysis because of its Comatose ability. Zygarde's Safeguard will make it difficult to inflict sleep, so be patient and keep trying.
If you caught Zygarde, leave the cave and go to the Aether Foundation building in Route 16 on Ula'ula Island. Inside, Dexio will challenge you to a battle. He has a level 63 Espeon, a level 63 10% Forme Zygarde, a level 63 Alolan Raichu, a level 63 Slowking, a level 63 Alakazam, and a level 63 Metagross. You get 8820 Pokédollars for winning.
After the battle, you get the 10% Forme Zygarde, and the Zygarde Cube, which has 40 cells in it.
You can now use the Reassembly Unit in this building. Check on the console to use it. To add more Cells to Zygarde, make sure that there is at least one Zygarde in your party, then choose Assembly, then choose Using Zygarde and the Zygarde Cube. Then choose Zygarde from your party. This will upgrade the chosen Zygarde without changing its data.
If you do not have a Zygarde in your party or Boxes, or you just want to create a new Zygarde, then choose Assembly, then choose Using the Zygarde Cube only. The machine will create a Forme of Zygarde. The Formes that you can create are 10% Forme (requires 10 total Cells), the 50% Forme (requires 50 total Cells) and Complete form (requires all 100 Cells).
If you do Separation, it is like releasing Zygarde into the wild, but the Cells go back into the cube for you to create another Zygarde. The new Zygarde will not retain anything (e.g. levels, stats, etc.) that the previous Zygarde had.
Poni Plains, Continued
Back in Poni Plains, go east from Poni Meadow, then keep going east past the sign. Go south, then go north up the path on the left to get an X Defense.
Then go north and you must battle Veteran Leon. He has a level 59 Skarmory, a level 59 Araquanid, and a level 59 Electivire. You get 5192 Pokédollars for winning.
If you have defeated all the trainers in Poni Plains, talk to the Ace Trainer in the southern part of the area to battle Ace Trainer Cole. He has a level 58 Druddigon, a level 58 Dragalge, and a level 59 Kommo-o. His Kommo-o is holding a Dragonium Z. You get 4012 Pokédollars for winning. Afterward, Cole gives you TM60 Quash.
Go north and there will be a cutscene. Looker will give you a Red Card.
Go north from there and you will reach Poni Coast.
To the north, there is a ramp to a small ledge. There is a Poké Finder spot there.
Break through the rocks with Tauros, then go northwest and go up the ramp on the left. Nearby, you can battle Youth Athlete Anton. He has a level 58 Alolan Sandslash. You get 1624 Pokédollars for winning.
Go north from there to find a hidden Max Revive.
Then go south and go down the one-way ledge to get TM97 Dark Pulse.
Southwest of that, you can battle Tourist Couple Steve and Reika. They have a level 59 Alolan Exeggutor and a level 59 non-Alolan Exeggutor. You get 5428 Pokédollars for winning.
Go south down the one-way ledge, then go north from there and you can battle Honeymooners Noriko and Devin. They have a level 59 non-Alolan Geodude, a level 59 non-Alolan Ninetales, a level 59 non-Alolan Sandslash, a level 59 non-Alolan Graveler, and a level 59 non-Alolan Golem. You get 7080 Pokédollars for winning.
Go north from the Honeymooners to find a Power Bracer.
North of that, you can battle Firefighter Aiden. He has a level 60 Octillery and a level 60 Clawitzer. You get 2400 Pokédollars for winning.
Go east and break through the boulder, then go north.
Up ahead, you can battle Scientist Kyle. He has a level 61 Ditto and a level 61 Porygon-Z. You get 2928 Pokédollars for winning.
Up ahead, across the bridge, there is a Power Band.
Nearby, you can battle Veteran Sheri. She has a level 63 Jellicent, a level 63 Pyroar, and a level 63 Froslass. You get 5544 Pokédollars for winning.
Go south across the bridge, then go west through the grass, then go north. Just before the next bridge, there is a Guard Spec. to the left.
Go north up the bridge and you can battle Backpacker Yuho. She has a level 61 Ambipom. You get 1464 Pokédollars for winning.
Go north and you can battle Black Belt Tracy. He has a level 62 Hawlucha and a level 62 Machamp. You get 1984 Pokédollars for winning.
Next to the Black Belt, there is a Full Restore.
South of the Black Belt, there is a hidden PP Up.
Go east from the Black Belt to find a Misty Seed.
Go south from there and you battle Punk Pair Marie and Troy. Marie has a level 61 Lycanroc and Troy has a level 61 Honchkrow. You get 3904 Pokédollars for winning.
Go south from there to get a Metal Coat.
Go back the way you came, and go north from the Black Belt, across a bridge.
Go north and you must battle Veteran Duo Tsunekazu and Nobuko. Tsunekazu has a level 63 Houndoom, a level 63 Magmortar, and a level 63 Volcarona. Nobuko has a level 63 Comfey, a level 63 Whimsicott, and a level 63 Lilligant. You get 11088 Pokédollars for winning.
The Punk Guy up ahead will trade you his Tauros in exchange for your Bewear.
Go north to arrive at the Battle Tree. It gets added to the destinations that you can fly to.
Go north and a cutscene will take place. You will be asked which of the two people you want to battle. You can only battle one of the two right now, but you can also battle them later by battling at the Battle Tree. Blue heals your pokémon before the battle. Here are each of their details:
Red has a level 74 Pikachu, a level 69 Lapras, a level 69 Snorlax, a level 70 Charizard, a level 70 Venusaur, and a level 70 Blastoise. You get 19600 Pokédollars for winning.
Blue has a level 69 Alakazam, a level 69 Machamp, a level 69 Aerodactyl, a level 69 non-Alolan Exeggutor, a level 69 Gyarados, and a level 69 Arcanine. You get 19320 Pokédollars for winning.
Battling in the Battle Tree
In the Battle Tree, you can have Single, Double, or Multi Battles. You will do consecutive battles until you are defeated or you take a break. You win BP each time you win a battle. You can use the BP to purchase items to the left of the Battle Tree receptionist, such as evolution items, battle items, and Mega Stones.
If you defeat 20 consecutive trainers, you will battle a special trainer afterward, and Super Battles will be unlocked.
If you have hatched at least 20 eggs, there is an Ace Trainer in the Battle Tree area who will upgrade the PC Boxes to add a "Judge" button in the bottom-right corner when you are viewing your PC Boxes. This will show a graph representing the selected pokémon's Individual Values (or IVs). IVs are bonuses to the pokémon's stats. These bonuses are permanent and are set from the moment the pokémon is encountered in the wild or is received in an egg. "Best" means that the IV is 31. "Fantastic" means that the IV is 30. "Very Good" means that the IV is in the range of 26 to 29. "Pretty Good" means that the IV is in the range of 16 to 25. "Decent" means that the IV is in the range of 1 to 15. "No Good" means that the IV is 0.