Mareep can be found on Routes 32, 42 and 43. Flaaffy can also be found on Routes 42 and 43. It is most common on Route 42, and generally tends to be more common during the daytime rather than at dawn or night. This line is exclusive to Gold and Silver, and cannot be found in Crystal.
An emblematic Pokémon for all Johto players, Mareep is the go-to choice for anyone who wishes to have an Electric-type in the region. It is by far the most common of all, it can be accessed from a very early point in the game, and it evolves quickly, as well as having excellent stats - almost beastly for the setting it is found in. The substantial lack of Earthquakes until much later in the game, as well as the general absence of major threats to Electric-types, make Ampharos' bulk even greater than its defenses nominally indicate, and it is one of the least likely Pokémon to die on any player that is sensible and not too careless. There is much that Ampharos has to offer in this game, and in many other games as well.
Gym #2 - Bugsy (Azalea Town, Bug-type): Flaaffy is excellent in this matchup. Aside from beating Metapod and Kakuna, which is not a difficult task to accomplish, it gets the best of Scyther very easily if it already knows Thunder Wave: a first-turn paralysis and ThunderShock spam will averagely 3HKO it, and Scyther can only KO at the fourth consecutive turn of Fury Cutter.
Rival (Azalea Town): Flaaffy's ThunderShock disposes of Gastly and Zubat in an average of two hits; Croconaw is 3HKOed. Quilava's Ember is about as powerful as ThunderShock, but Flaaffy is slower, and needs to use Thunder Wave first, in order to win. Flaaffy can also paralyse Bayleef before switching out, but should not attempt to actually fight it, as its Razor Leaf is strong and has a high critical hit ratio.
Gym #3 - Whitney (Goldenrod City, Normal-type): It is advised to invest on a ThunderPunch TM before fighting against Whitney. This will allow Flaaffy to 3HKO Clefairy, significantly reducing the threat of it Metronoming either Selfdestruct or Explosion, the only moves that can kill Flaaffy from full health; Flaaffy can also Thunder Wave it on the first turn, to improve its chances of dodging hits. Miltank is averagely 4HKOed by ThunderPunch, but can 3HKO with Stomp, and Rollout outdamages ThunderPunch starting at the third turn; Flaaffy can win by paralysing it on the first turn, then spamming ThunderPunch and hoping that Miltank stays paralysed at least one turn, which will break the Rollout streak in time to avoid a disastrous fate.
Rival (Burned Tower): Flaaffy can 2-3HKO Haunter with ThunderPunch, which is just strong enough to prevent it from using its dangerous Mean Look and Curse combo. Zubat is 1-2HKOed by ThunderPunch, and Magnemite is 2HKOed by Fire Punch. Croconaw is easily 2HKOed, and Quilava can be beaten by paralysing it first, though Bayleef will require an average of three hits; its Razor Leaf is nowhere near as strong as Fire Punch, but Flaaffy should be shielded from critical hits if its health is below half.
Gym #4 - Morty (Ecruteak City, Ghost-type): Flaaffy 2HKOs Gastly with ThunderPunch. It can also 2-3HKO the level 21 Haunter with the same move, but should be wary of its Hypnosis and Curse combination, which can make it difficult to hit with the right dosage of luck; however, if Flaaffy manages to land one hit, using Curse will generally off Haunter, or almost. The level 23 one requires an average of three hits, but also does not know Curse, only Mean Look; Flaaffy should switch out if a Curse has been laid upon it, but can continue the battle otherwise. Flaaffy should preferably not fight Gengar; although Thunder Wave is a very useful asset against something as fast as Gengar, Mean Look and Shadow Ball spam will do Flaaffy in before it can KO with ThunderPunch, unless paralysis kicks in. This is also assuming that Flaaffy will manage to paralyse Gengar at all, which is not guaranteed, given Gengar's higher Speed and Hypnosis.
Gym #5 - Chuck (Cianwood City, Fighting-type): ThunderPunch 2-3HKOs Primeape easily, and 2HKOs Poliwrath. Ampharos should start off the fight against Poliwrath with Thunder Wave as a safety measure, as it makes Hypnosis easier to work around, and its Mind Reader and DynamicPunch combination much harder to use; a DynamicPunch from Poliwrath averagely 3HKOs Ampharos, which may become problematic if Ampharos also hits itself in confusion.
Gym #6 - Jasmine (Olivine City, Steel-type): Ampharos can 1-2HKO both of the Magnemite with Fire Punch, and also 2-3HKOs Steelix, which lacks Ground STAB altogether and is therefore not threatening.
Rocket Executive battle #1 (Team Rocket HQ): Both Flaaffy and Ampharos have a good matchup. ThunderPunch OHKOs Zubat regardless of evolutionary stage, 2HKOs or 3HKOs Raticate depending on whether Flaaffy is evolved or not, and ThunderPunch 1-2HKOs Koffing, which is a non-issue even as Flaaffy because Flaaffy can take a non-critical Selfdestruct (Ampharos is capable of taking a critical hit, too).
Rocket Executive battle #2 (Team Rocket HQ): Flaaffy scores 2-3HKOs with ThunderPunch and Fire Punch all across the board, without taking any risks. Ampharos averagely KOs each Pokémon in one less hit.
Gym #7 - Pryce (Mahogany Town, Ice-type): Ampharos' ThunderPunch 1-2HKOs Seel and 2HKOs Dewgong; Fire Punch averagely 3HKOs Piloswine. The latter knows no Ground moves, so Ampharos is not at a risk against it; its Blizzard deals little more than half the damage Fire Punch can deal.
Rocket Executive battle #3 (Goldenrod Radio Tower): Each Koffing can be 2HKOed with ThunderPunch, but Ampharos cannot take more than one Selfdestruct. It must also keep away from Weezing, whose Explosion is a near-OHKO; it can, however, Thunder Wave it before switching out.
Rival (Goldenrod Underground): ThunderPunch 1-2HKOs Golbat, Fire Punch averagely OHKOs Magnemite. Haunter and Sneasel are both 2HKOed. Feraligatr is 2HKOed by ThunderPunch, Quilava and Meganium are 2-3HKOed depending on damage variation.
Rocket Executive battle #4 (Goldenrod Radio Tower): Murkrow goes down to one ThunderPunch. Arbok and Vileplume are both 2-3HKOed by the right elemental punch.
Rocket Executive battle #5 (Goldenrod Radio Tower): ThunderPunch 2HKOs Houndour and Koffing. Against Houndoom, the move is a 3-4HKO, so using Thunder Wave beforehand is advised, as it will help Ampharos avoid Bite-induced flinching and/or reduce the impact of possible Smog poisoning.
Gym #8 - Clair (Blackthorn City, Dragon-type): Ampharos' ThunderPunch is actually stronger than any of the Dragonair's moves by a substantial amount, dealing almost 50% more damage despite being not very effective. Thus, Ampharos can take on all three Dragonair, potentially; it needs Thunder Wave as well, and the fight will still be painful, because all three of the Dragonair also know the move. Winning against Kingdra is more complicated, but less tedious: Ampharos still needs to open with Thunder Wave, then switching to ThunderPunch until Kingdra is KOed. Kingdra's Hyper Beam is a 3HKO against Ampharos' average 4HKO ThunderPunch, but Hyper Beam requires recharge turns, and paralysis is helpful.
Rival (Victory Road): Ampharos scores 2HKOs all across the board against the rival's non-starter Pokémon, either with Fire Punch (Magneton) or ThunderPunch (everything else). The starters are respectively 2HKOed in the case of Feraligatr, or 3HKOed with ThunderPunch if Typhlosion, Fire Punch if Meganium.
Elite Four Will (Indigo Plateau, Psychic-type): ThunderPunch 1-2HKOs both of the Xatu, 2HKOs Slowbro, and Fire Punch 2HKOs Exeggutor and Jynx.
Elite Four Koga (Indigo Plateau, Poison-type): Fire Punch is a 2HKO against Ariados and Venomoth, and also OHKOs the otherwise dangerous Forretress, carrier of Explosion. Muk can be 3-4HKOed, though Ampharos should resort to Thunder Wave first, to minimise the probability of getting badly poisoned by either Toxic or Sludge Bomb, as well as reducing the likelihood of Muk using Minimize. Crobat knows Double Team and Toxic, but if kept healed, Ampharos has nothing to fear against it, and will 2HKO with ThunderPunch.
Elite Four Bruno (Indigo Plateau, Fighting-type): Ampharos should lead off against Hitmontop with Thunder Wave, which minimises the probability of its Dig carrying through with execution. Despite the type effectiveness, Dig can only KO Ampharos in five or more turns, either way; ThunderPunch, instead, is a 3HKO, also against Hitmonchan and Hitmonlee. Hitmonlee should be paralysed first, as its Swagger can impair Ampharos' sweeping. Ampharos should avoid Onix, due to its unfortunate typing, but may be able to overcome Machamp; Thunder Wave support is essential, as Cross Chop 3HKOs - whereas ThunderPunch oscillates between 3HKO and 4HKO - and also has a high critical hit ratio. Ampharos must be kept healthy at all times until Machamp's Cross Chop PPs run out.
Elite Four Karen (Indigo Plateau, Dark-type): Umbreon's Mean Look and Sand-Attack may become annoying in the long run, but Ampharos can outdamage it easily; if in-battle items are allowed, an X Accuracy will solve all of Ampharos' accuracy problems, and Thunder Wave will make the job easier as well. Ampharos also OHKOs Murkrow with ThunderPunch and 2HKOs Vileplume with Fire Punch. Gengar is an average 2-3HKO, but must be paralysed first; its Destiny Bond is likely to kill Ampharos if Gengar can outspeed. Lastly, Houndoom is also a 3HKO, and can be defeated more easily with the help of paralysis.
Champion Lance (Indigo Plateau, Flying-type): Gyarados is OHKOed by ThunderPunch, which also 2HKOs Aerodactyl and Charizard. Ampharos can also take on either or both of the level 47 Dragonite, throwing a Thunder Wave at them before starting the ThunderPunch spam; their Hyper Beam can 3HKO at best, and ThunderPunch is an average 4HKO. The ace is more dangerous, its Hyper Beam hitting the (unlikely) 2HKO range, but Ampharos can still paralyse it and then switch out, or remain on the battlefield and be healed as needed to prevent critical hits from killing it before it gets the job done.
From this point onwards, you can fight the gyms in any order, though you will need to retrieve the Machine Parts from the Cerulean City gym before you have access to the earlier portion of Kanto. Feel free to anticipate or postpone any battles as needed.
Gym #9 - Brock (Pewter City, Rock-type): ThunderPunch 1-2HKOs Omastar and Kabutops, but Ampharos must avoid Graveler and Rhyhorn, both of which pack Earthquake. Onix has no Ground STAB, and Ampharos can theoretically beat it, but Fire Punch deals underwhelming amounts of damage and Sandstorm and Bide combined are much more likely to work than Fire Punch spam; a better Pokémon should be used against it.
Rival (Mt. Moon, optional): Sneasel, Golbat and Magneton are 2HKOed by either Fire Punch or ThunderPunch; the latter 2-3HKOs Gengar and Alakazam. Alakazam should be paralysed first, as it knows Recover and can work around ThunderPunch damage if it outspeeds. Feraligatr is still 2HKOed by ThunderPunch, Typhlosion is averagely 3HKOed, and Meganium is 2-3HKOed by Fire Punch.
Gym #10 - Misty (Cerulean City, Water-type): ThunderPunch 2HKOs Golduck, Lapras and Starmie, but Quagsire must be avoided due to Earthquake. Thunder Wave should also be the opener against Starmie, whose Confuse Ray and Recover combination can otherwise work around sheer ThunderPunch damage.
Gym #11 - Lt. Surge (Vermilion City, Electric-type): Raichu, Magneton and Electabuzz all eventually go down to Fire Punch, and their Electric STAB barely tickles Ampharos. The two Electrode are harder to beat; they can spam Double Team and then use Explosion, and though Ampharos has sufficient bulk to take one, it cannot take two, or a critical hit from that move. Ampharos should use Thunder Wave against them, and err on the side of caution while battling.
Gym #12 - Erika (Celadon City, Grass-type): Fire Punch scores 2HKOs all across the board except for Bellossom, which is 2-3HKOed. If any of Erika's Pokémon put up Sunny Day, Fire Punch will also 2HKO Bellossom.
Gym #13 - Janine (Fuchsia City, Poison-type): Crobat and Ariados are OHKOed by ThunderPunch and Fire Punch respectively, whereas the two Weezing are 2HKOed by ThunderPunch, and Venomoth by Fire Punch. Ampharos, however, can only take one Explosion, and should not fight the second Weezing unless healed.
Gym #14 - Sabrina (Saffron City, Psychic-type): ThunderPunch is an average 3HKO against all of Sabrina's Pokémon. While Mr. Mime can be simply attacked right away, Espeon and Alakazam should be Thunder Waved first, as their Sand-Attack and Recover can make it hard for Ampharos to hit, or defeat them. Ampharos should also switch out of battle, and then back in, if its accuracy is below normal after fighting Espeon.
Gym #15 - Blaine (Seafoam Islands, Fire-type): ThunderPunch is an average 3HKO against all of Blaine's team, and can outdamage Magmar's Fire Punch even under Sunny Day. Rapidash's Fire Blast, instead, can 2HKO under the sun, but Ampharos can lead with Thunder Wave and then put up Light Screen to maintain its advantage throughout the battle.
Gym #16 - Blue (Viridian City): ThunderPunch 2HKOs Pidgeot and 1-2HKOs Gyarados. Fire Punch normally 3HKOs Exeggutor, but can 2HKO if Exeggutor uses Sunny Day, which it likely will, because its only STAB move is SolarBeam. Arcanine's Flamethrower slightly outdamages Ampharos' ThunderPunch, but Ampharos can use Thunder Wave and Light Screen to rebalance the matchup; Arcanine still does have ExtremeSpeed, however, so Ampharos should be careful anywhere near one quarter of its health or below. Alakazam can be beaten using the same strategy as Arcanine, and is significanly less dangerous, its Psychic only being in the 3-4HKO range and having no priority moves. Ampharos must avoid Rhydon, due to Earthquake.
Rival (Indigo Plateau, optional): Sneasel, Magneton and the newly evolved Crobat are still 2HKOed by ThunderPunch or Fire Punch, depending on typing; Gengar and Alakazam are 3HKOed, and should both be paralysed before attacking, to avoid their Curse and Recover shenanigans respectively. ThunderPunch 2HKOs Feraligatr and Meganium is 3HKOed by Fire Punch; Typhlosion requires an average of four hits, but Thunder Wave and Light Screen can help whittle it down without taking much damage.
Red (Mt. Silver): Pikachu is 3HKOed by Fire Punch and deals pitiable damage. Thunder Wave is the best opener against Espeon, whose Mud-Slap can easily make it hard to hit; if Ampharos manages to keep its accuracy high enough, and/or an X Accuracy is used, ThunderPunch will 3HKO easily. Venusaur is 3HKOed by Fire Punch, but also very likely to use Sunny Day during the battle, as its entire moveset is based on it; if Sunny Day is used, Fire Punch becomes a 2HKO. ThunderPunch is a 2HKO against both Charizard and Blastoise, regardless of weather conditions; Charizard cannot 2HKO Ampharos even with a sun-boosted Flamethrower, nor can Blastoise with Surf and the aid of rain. Snorlax is the only Pokémon on Red's team that Ampharos has trouble fighting, its Body Slam consistently outdamaging ThunderPunch and Rest foiling any attempts at Thunder Wave; a physical set running Curse may work against it, but is discouraged, as it would sacrifice Ampharos' usefulness against the rest of Red's Pokémon.
Mareep's initial moveset, when caught at the earliest possible location, consists of Tackle and Growl. It then gets ThunderShock at level 9, which is very good STAB for the early game. The evolution may optionally be postponed until level 16 to have Flaaffy learn Thunder Wave early; Flaaffy gets it too, but only two levels later. The next move is only at level 27, and it is Cotton Spore, 100% useless since Mareep liners get access to Thunder Wave by level. Unlike Mareep, Flaaffy's evolution should not be delayed, as Ampharos learns ThunderPunch naturally at level 30, right after evolving; if it cannot evolve at that level for some reason, the move can still be learned, but only through the Goldenrod Dept. Store TM. Light Screen comes at 42, and is also a very useful move, considering that Ampharos only really learns two offensive moves that it should keep for the long haul, and the other two slots are best filled by support moves, for which Light Screen is a perfect candidate. Lastly, there is Thunder at level 57, but that is a move Ampharos will likely not have access to until the postgame; Thunder is also very inaccurate, and thus unreliable, unless Ampharos also knows Rain Dance.
The TM pool is fairly varied, but mostly on the tactical side. The only non-Electric special move Ampharos learns is Fire Punch, which is accessible starting in Goldenrod, and it provides good coverage for Grass-types. The Rain Dance and Thunder combo is also possible whenever Thunder is learned, but Rain Dance itself does not get along well with Fire Punch, and greatly limits Ampharos' offensive potential. Curse is a viable hipster option in fights where all else fails, as Ampharos' Speed is forgettable and the bulk is very much real. Toxic is good for more defensive sets, but it renders Thunder Wave useless, so Ampharos should only run one between Toxic and Thunder Wave. If running a Curse and Light Screen based set, and/or on a nuzlocke that limits or prohibits the usage of healing items in battle, Rest is also great.
Pokémon that are good against Ground-types: Water-types, Grass-types, and Flying-types are all useful against Ampharos' sworn enemies, in different ways. Flying-types provide a Ground immunity but without the good offensive response, while Water-types are good offensively but defensively neutral; Grass-types are the best individually, but not as useful as Water-types on a general level.
Fast hitters: Ampharos' slowness will generally not be a problem due to its good bulk, but it is still useful to have at least one glass cannon on the team; they can dispatch other fast Pokémon that Ampharos may struggle against, particularly those that inflict status conditions.
Minimum stats are calculated with 0 EVs, IVs of 0, and a hindering nature, if applicable.
Maximum stats are calculated with 252 EVs, IVs of 31, and a helpful nature, if applicable.
Mareep Line Ratings
At what point in the game should I be evolved? Having a Flaaffy by the time Bugsy is fought would be ideal, as the matchup against Scyther is definitely in its favour. As for Ampharos, evolving before Chuck is good; Ampharos serves a good purpose as a Poliwrath counter. In general terms, the evolution should not be delayed in either case; one of the major perks of this line is the early evolutionary levels, so there is no point waiting.
How good is the Mareep line in a Nuzlocke? Incredibly good, especially in a generation where not much can hit it physically, and Ground is the only type that Ampharos really fears. Johto does not even have much of it, which is part of what makes Ampharos so strong.
Resistances: Flying, Steel, Electric
Neutralities: Normal, Fighting, Grass, Water, Fire, Poison, Rock, Bug, Ghost, Psychic, Ice, Dragon, Dark