After the events that take place at the Champion Cup, you must revisit the Slumbering Weald.
Reach a New Area of the Slumbering Weald
Go through the Slumbering Weald as before. Eventually, you reach an area that you haven't been to before. The pokémon that you may see in this area are Corviknight, Munna, Orbeetle, and Weezing (Galarian Form). The pokémon that can be found in rustling patches of grass are Butterfree, Corviknight, Munna, Orbeetle, Stunfisk (Galarian Form), and Weezing (Galarian Form).
Look for a sparkle in the area where the path splits into northwest and northeast. There is a sparkle there. Check on it to get a Full Restore.
At the split, go northeast first. When the path splits again, go northwest to find a Misty Seed. Then go back to the nearest fork in the path and go northeast to find some water. The pokémon that you can encounter by fishing here are Barboach, Magikarp, and Whiscash.
You can ride the Rotom Bike in the water. Go south down the river to find a Life Orb.
Go north in the river, then west to get back on solid ground, then go southwest to the grassy area. Go through the grass until you can go northwest. When the path splits, go northwest to find a Mental Herb.
Go north from there and the path will split once more. First, go northeast and walk across the log. Check the north edge of the area to find a sparkle. Check on it to get an Elixir.
Go east from there to find TM86 Phantom Force.
Go back across the log, then go slightly west until you can go north. There are two northern paths. The one on the right has a Stunfisk (Galarian Form) hiding in the ground, and north of the Stunfisk, there is a Smoke Ball.
Then go south until you can go west, and go north from there. Approach Hop and there will be a cutscene. Afterward, go north until there is another cutscene. After that, go north again, and there will be another cutscene. Go north once more, and if you are playing Pokémon Sword, you receive the Rusted Sword. If you are playing Pokémon Shield, you receive the Rusted Shield.
After that, you can talk to Hop if you want to go directly to Hammerlocke. If you don't go with Hop, you can approach Hammerlocke Stadium when you are ready to proceed with the story. There will be a cutscene.
When you are ready, go north into Hammerlocke Stadium.
In the stadium, approach Oleana. After the cutscene, use the elevator in Hammerlocke Stadium to go to the Energy Plant.
Go west, then north and go past Hop. There will be a cutscene. Then you will battle Macro Cosmos's Rose, who has a level 55 Escavalier, a level 55 Ferrothorn, a level 55 Perrserker, a level 56 Klinklang, and a level 57 Copperajah that he Gigantamaxes at the first turn. You get 11400 Pokédollars for winning.
After you defeat Rose, go south. If you are ready, you can talk to Hop to go up the elevator. If not, you can go outside and prepare, then go back down the elevator in Hammerlocke Stadium and talk to Hop to proceed.
At the top, go up the stairs and go north, and there will be a cutscene. Afterward, you must defeat the level 60 Eternatus. You can't catch it, so just focus on defeating it.
After you defeat it, there will be a cutscene.
Your pokémon will be healed up, and you will have a Max Raid battle with Eternatus (Eternamax Form). For the first three turns, your moves won't work, so just pick any moves until there is a cutscene. When the battle resumes, focus on defeating Eternatus. After it is defeated, catch Eternatus with whichever type of pokéball you prefer. It is guaranteed to work.
Afterward, there will be a cutscene.
When you're ready, enter the Wyndon Stadium and talk to the person behind the counter. There will be a cutscene, then the battle will begin.
Champion Leon has a level 62 Aegislash, a level 62 Dragapult, a level 63 Haxorus, a level 64 pokemon (if you chose Scorbunny, he has Mr. Rime; If you chose Grookey, he has Seismitoad. If you chose Sobble, he has Rhyperior), a level 64 starter pokémon that is strong against the starter that you chose (if you chose Scorbunny, he has Inteleon; If you chose Grookey, he has Cinderace. If you chose Sobble, he has Rillaboom), and a level 65 Charizard that he Dynamaxes at the first turn. You get 15600 Pokédollars for winning.
Congratulations! You won! Enjoy the ending! After the credits roll, the game will automatically save, and you will return to the title screen. The next time you play, you will start the Post-Game.