Mt. Moon is full of several new Pokémon as well as the menacing Team Rocket. Team Rocket is after Pokémon fossils, no doubt as part of some diabolical scheme. It's up to you to stop them from raiding these lost paleontological treasures!
This cave is full of Zubat, but once you have a Pikachu who can hit them with its super effective move, Thunder Shock (or another strong Pokémon at the head of the roster), you'll find them to be little more than an annoyance. Deeper levels of the dungeon have Zubat that use the Supersonic skill to confuse your Pokémon, but that can be shaken simply by swapping the confused fighter for another.
Geodude is a bit trickier. They're weak to Grass and Water, so Squirtle's Bubble or Water Gun (can learn by level 15) and Bulbasaur's Vine Whip can wipe them out quickly. Also, Butterfree and its Confusion attack. If you don't have either of these, you can just grab TM12 and use it to teach Water Gun to one of your Rattata, Jigglypuff, Nidorina or Nidorino. You can also use Charmander/Charmeleon's Ember attack. Although it may be fire and say that it's ineffective, it does considerable amount of damage compared to most other attacks. Alternatively, if you have a Nidoran (male or female), it will learn Double Kick at level 12 (Yellow version only), which is super effective to Rock types because the move is a Fighting type. Remember that Poison- and Rock-type attacks don't do very well against Geodude, and Electric attacks have no effect at all.
Also feel free to use TM01, which teaches Mega Punch. It's a pretty powerful Normal-type attack, although it's slightly inaccurate. It will be outclassed by other attacks such as Strength, Body Slam, and Double-Edge later on.
Mt. Moon B1 encounters
Zubat
60%
60%
65%
Geodude
26%
26%
20%
Paras
10%
10%
10%
Clefairy
4%
4%
5%
More Battles Await
Two nasty surprises await at the end of Mt. Moon (to get to the end, take ladder C to F to G). Red and Blue players may simply want to avoid Rocket #3, since his Level 16 Raticate can easily slay a Pokémon with Hyper Fang. Yellow players can't avoid their extra battle, though. Use an Escape Rope and come back with a healed party, or heal up with Potions as needed. Yellow players should also watch out for the infamous Team Rocket Duo Jessie and James, who will unexpectedly ambush you at the end after the battle over the fossils.
Which fossil should you take? When you get the Dome Fossil cloned (much later in the game), it will become Kabuto. The Helix Fossil will yield an Omanyte. You can't go wrong with either one, since chances are you won't want to exchange a member of your high-level team by that time. To get the other one, you'll either have to trade for it, or receive one as a prize in Pokémon Stadium.
Mt. Moon B2 encounters
Zubat
54%
54%
60%
Geodude
25%
25%
15%
Paras
15%
15%
15%
Clefairy
6%
6%
10%
Map key:
1
Rocket
330
Sandshrew
LV11
Rattata
LV11
Zubat
LV11
2
Rocket
360
Zubat
LV12
Ekans
LV12
3
Rocket
390
Raticate
LV16
Rattata
LV13
Zubat
LV13
Trainers and
4
Rocket
390
Rattata
LV13
Zubat
LV13
5
Super Nerd
300
Grimer
LV12
Voltorb
LV12
Koffing
LV12
6
Jessie & James
420
Ekans
LV14
Meowth
LV14
Koffing
LV14
Items
A
TM 01
B
Ether
C
HP Up
D
Moon Stone
Secrets of the Moon Stones
The Moon Stone you pick up here is a crucial item, and one of only five Moon Stones in Pokémon Red, Blue, and Yellow. Moon Stones are the one and only way to make certain Pokémon evolve, of which there are exactly four: Nidorino (Nidoking), Nidorina (Nidoqueen), Jigglypuff (Wigglytuff) and Clefairy (Clefable). But don't go using that Moon Stone quite yet: all four of these Pokémon stop learning moves once they're evolved (although the Nidos do get one new move each: Nidoking gets Thrash and Nidoqueen gets Body Slam at level 23, which are both excellent moves), so before you evolve any of them, check the Pokédex and make sure they've learned all the skills you want out of them. Note, though, that all four can still learn a wide variety of skills from TMs and HMs.
There is one Moon Stone here in plain sight, and another hidden in one of the basements. Before you take on Trainer #5 near the two fossils, search the dead end marked D for a second Moon Stone.
#41 Zubat
#74 Geodude
Zubat isn't that good. It's a Poison and Flying-type (although it doesn't learn any Poison attacks), so it's weak to many types. Leech Life's draining ability is useful, but is extremely weak at 15 power. It's hard to damage most things with it. It does however have the status move Supersonic, which can confuse opponents despite its poor accuracy, which can be later upgraded with Confuse Ray that has almost perfect accuracy.
Geodude is painfully slow, and its double weaknesses to Grass and Water can be devastating. However, its Attack and Defense can grow to high levels, and it can gain Rock and Ground attacks without the use of TMs. Geodude's strength against Electric, Flying, Fire and Normal attacks is also very useful throughout the game. While it is needed to trade as a Graveler for it to evolve into its final evolution, Golem, it can become a great Pokémon to use overall in teams.
#35 Clefairy
#46 Paras
Clefairy and Jigglypuff are very similar; both are pink, puffy Pokémon that evolve with a Moon Stone, have a ton of HP, and can use just about any TM. However, Clefairy has much better stats overall. Clefairy isn't very useful for adventuring, but can become fairly useful in link battles with the help of TMs. Clefairy is definitely better than Jigglypuff, and it can learn Water Gun from that TM12 you obtained recently. Note that if you are playing Yellow, you may wish to catch a second Clefairy because later on Route #2 you can trade the extra Clefairy for a Mr. Mime.
A unique Bug and Grass-type Pokémon, Paras is however, very weak in general. Many claim it's a "Psychic stopper", given its Bug-type (which is the only type in Generation I whose attacks are super effective on the dominating Psychic-types), lack of a Poison-type, and its Leech Life Bug-type attack. Unfortunately, this just isn't the case. Leech Life is extremely weak no matter what, and Paras' stats are mediocre. Paras' only saving grace is Spore, the only Sleep-inducing attack with a nearly perfect accuracy that is great for catching Pokémon and useful in Pokémon battles. Unfortunately, since Paras and its evolution Parasect are so slow, it will likely lose most of its HP before hitting anything with it.