1F
| Encounters in the area | ||||
|---|---|---|---|---|
| 1F and B1F | ||||
| Pokémon | Types | Level | Rarity | |
 |
Clefairy | 5-10 | 4% | |
 |
Zubat | 5-10 | 40% | |
 |
Paras | 5-10 | 15% | |
 |
Geodude | 5-10 | 40% | |
 |
Onix | 5-10 | 1% | |
| Rare Encounters | ||||
| Pokémon | Types | Level | Rarity | |
 |
Chansey | 5-10 | Rare | |
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160
400
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As you enter Mt. Moon, you’ll encounter two of the shady characters that you might have seen blocking the way in Viridian City earlier. They’ll say a few things and then run off further into the cave.
You could follow them, but you might first want to check out the southwestern part of the floor. There’s a Potion right around the corner there and Bug Catcher Kent guarding 5 Great Balls up to the north.
Return to the entrance and this time head east. Along that path you’ll find Lass Evelyn blocking the way. Fight her and then continue onwards. You’ll find the red-haired lady from earlier before she runs further to the north.
There’s a lot of optional areas to explore in Mt. Moon, so keep that in mind. You should see a ladder leading down nearby, which takes you down to B1F and then B2F, but there’s also some stuff to pick up in the south and southeast.
Go ahead and make your way to the south first until you find Super Nerd Jovan next to an Awakening. Grab that and then head to the east to pick up an Ether, an item which restores your Pokémon PP of a single move by 10. Fight against Youngster Robby nearby but make sure you stay along the eastern side of the cave to find a Repel.
Keep going north until you find the northeast corner of the room, then head back to the southwest to find the ladder from earlier. Go ahead and take the optional ladder down to B1F.
B1F
It’s a relatively short, straightforward tunnel leading you to another ladder that takes you to B2F. Follow the path and make your way downstairs.
B2F
| Encounters in the area | ||||
|---|---|---|---|---|
| B2F | ||||
| Pokémon | Types | Level | Rarity | |
|
Clefairy | 5-10 | 9% | |
 |
Clefable | 5-10 | 1% | |
|
Zubat | 5-10 | 40% | |
|
Paras | 5-10 | 15% | |
|
Geodude | 5-10 | 34% | |
|
Onix | 5-10 | 1% | |
| Rare Encounters | ||||
| Pokémon | Types | Level | Rarity | |
|
Chansey | 5-10 | Rare | |
252
Down here you’ll find a suspicious man in a black uniform with the same “R” logo as the shady characters from earlier. He’s from Team Rocket, a group of Pokémon gangsters! Uh oh! Thankfully his Rattata is pretty weak.
There’s a Rare Candy up on the ledge just to the east, but a much better treasure is the hidden Moon Stone in the center of the crater just to the south of that. The Moon Stone can be used to evolve Pokémon like Nidorina and Nidorino — the evolutions of Nidoran♀ and Nidoran♂ — as well as Clefairy and Jigglypuff. This Moon Stone also respawns daily, meaning if you wait a day, you can come back to get another one in this same spot.
That’s all down here. Make your way back up to the ladder on 1F.
1F
160Directly north of the ladder is a crater that has a hidden Stardust in it. It respawns daily. Definitely pick that up, because the Stardust can be sold for a lot of money. Keep going west and you’ll find Lass Miriam. Watch out, because her Clefairy loves to use Sing to put your Pokémon to sleep!
Just a bit further and you’ll find another ladder along with the blue-haired man from earlier who tells you to stop following him. He then runs off once again, but leaves you free to check out the ladder. Once again, this ladder is optional, but you might as well check it out.
B1F
There is basically nothing in this tiny room other than a ladder taking you down to B2F.
B2F
There’s another hidden Moon Stone in the crater just to the east of the ladder, which also respawns daily, so make sure you pick that up before continuing so you’ll be able to evolve your Pokémon. Additionally, there’s a Nugget sitting on the ledge above that, which can be sold for a staggering 
5,000. Very nice!
Again, that’s all there is down here, so make your way back to 1F.
1F
160
400West of the ladder you’ll find Youngster Josh and just a little bit past him is Hiker Marcos. Fight either of them and then continue your way to the north to find the final ladder leading downstairs as well as a Pearl off in the corner.
Running low on Poké Balls? If you have less than 10 Poké Balls, you can talk to the man in the northeast corner of Mt. Moon 1F and he’ll give you 10 Poké Balls.
There are several other generous people like this throughout the world, so be on the lookout for them so you can continue to train up even if you run low or run out of Poké Balls.
Now, head down the ladder to reach B1F once again.
B1F
Head south to find Meowth. That rhymed! Meowth will then run off in the direction you should be headed. Yet again, there’s nothing really here except a path leading to the ladder down to B2F.
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Thankfully, this should be your last time on B2F — you’re getting close to the end, don’t worry! Head over to the north to pick up a Revive, which is pretty handy. Then make your way to the east and fight against the Team Rocket Grunt.
Fight the Grunt, go up the slope, grab the Potion in the corner, and then head south. You’ll find the three characters from earlier, but they’re preoccupied with looking down the cliff, so don’t worry too much about them and just continue following the path.
It’s a rather long and straightforward path, but follow it until you find another Team Rocket Grunt as well as another Revive nearby.
To the north is another Super Nerd, and this one will fight you over the fossils he’s found. After beating him, he’ll let you pick one of the two fossils. Be mindful that you can only pick one of the fossils, so choose wisely: by picking the Helix Fossil, you will eventually get an Omanyte; by picking the Dome Fossil, you’ll eventually get a Kabuto. You won’t get either for a very long time, though, and both Pokémon are Water/Rock-types, so pick whichever you prefer.
Afterwards, you’ll be able to continue to the west and at the end you’ll finally face off against the trio of shady characters you saw throughout the cave. They introduce themselves as Jessie and James of Team Rocket. Prepare for trouble and make it double! Well, specifically, make it a Double Battle — the Pokémon in slot one (top-left) and slot two (top-center) will fight in the battle.
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This is the first time you’ve had a Double Battle, so it’s a little different. Some moves, like Ekans’s Acid, will hit multiple targets, but for most moves you’ll have to choose one of the targets. It’s better to focus on one Pokémon at a time so you can turn it into a two-on-one fight.
You can shake your Joy-Con or Poké Ball Plus after the fight to see a rather funny expression on your partner Pokémon’s face.
Head down to the ladder, climb it and the following ladder, and you’ll finally be free from Mt. Moon and reemerge on Route 4.