You must go to Coronet Highlands to quell the Electrode's frenzy.
Battle Adaman
Go outside and talk to Adaman to battle him. He has a level 36 Leafeon and level 18 Eevee.
Reach Fourth Star Rank
Before you can go to Coronet Highlands, you need to reach Fourth Star rank. As before, complete research tasks and catch new pokémon to earn points. Then talk to Cyllene in Galaxy Hall in Jubilife Village after you earn enough points to rank up. You will gain the ability to use Leaden Balls, pokémon up to level 50 will obey you, and you will learn the Leaden Balls recipe and Hyper Potions recipe.
Go to the Training Grounds
Once you are Fourth Star rank, go to the Jubilife Village Training Grounds and talk to Irida. There will be a cutscene.
Go to Coronet Highlands
Go to the Front Gate and talk to Ress, and choose the Highlands Camp in Coronet Highlands.
Go to Ingo
Make your way down the slopes to reach the bridge where Ingo is waiting for you. During the cutscene, say "Press On", then go into the cave.
Follow Ingo through the Cave
Ingo will lead the way through the cave. Be sure to follow him. After he sets up the torches, follow them through the cave until you reach the exit. Go outside.
Go to Ingo Again
Go to the guidance marker to find Ingo again. Approach Melli and there will be a cutscene.
You will battle Melli's level 40 Skuntank.
Go Through the Ruins
After the battle, go to the guidance marker to find Ingo. After the cutscene, make your way through the quarry. On the other side, be sure to accept the request from Eshim, Setting Up the Mountain Camp, to build a base camp here.
Go northwest from the base camp and talk to Ingo to proceed. You will battle Ingo's level 41 Machoke, level 41 Tangela, and level 42 Gliscor.
Afterward, you will be able to summon Sneasler to climb cliffs. You will get the Toxic Plate.
Scale the Cliffs with Sneasler
You can press left and right to switch between Wyrdeer, Ursaluna, and Sneasler. You can also press A when you are up against a cliff to summon Sneasler. If you are at the edge of a cliff, you can press Y to descend. You can also climb trees and walls and other structures.
With Sneasler's help, go to the guidance marker to find Melli. You will battle against Melli's level 44 Skuntank, level 22 Zubat, and level 22 Skorupi, all at the same time.
Quell the Electrode's Frenzy
Moonview Arena has been added as an instant travel location, so feel free to go to a base camp to heal up and prepare before you return to Moonview Arena to face Electrode.
Approach Melli to begin the encounter.
Avoid standing still. Electrode will create electricity orbs that follow you. While it is possible to hit Electrode with balms at this time, you will need to alternate with pressing Y to dodge away from the floating electricity orbs before they catch up to you. In addition, Voltorbs will appear in random locations and create small energy fields around themselves, so keep your distance from them.
Eventually, Electrode will charge up a large energy field. You need to avoid the area near Electrode (even if it looks like the safe area is near Electrode). Run to an edge of the area and continue running along the edge away from any following orbs, and press Y if needed to get out of the circle around Electrode, to avoid the burst of energy that the Electrode eventually creates in that area. Afterward, Electrode will be temporarily stunned, so you can throw a partner pokémon at it to do battle. Afterward, throw as many balms at the stunned Electrode as you can. The closer you are, the more quickly you can throw balms, but be ready to run away as soon as Electrode recovers.
Later, Electrode will also send out a blue orb, which moves much faster. You might not have enough time to throw balms when a blue orb is following you.
After the battle, you get the Zap Plate.
Report to Commander Kamado
Talk to Professor Laventon at a base camp to make your report and return to Jubilife Village. Enter Galaxy Hall and go up the stairs until you reach Commander Kamado. During the cutscene, the next mission, The Slumbering Lord of the Tundra, will begin.