Tympole and its evolutions can be found in both games. Tympole is found only in the outside area of Pinwheel Forest, while Palpitoad and Seismitoad is available in Route 8, Icirrus City, and in the Moor of Icirrus in every season except for winter.
How does it feel having a Pokémon with only one uncommon weakness and very well balanced stats? Great, of course, no less than what one would expect from Unova. Seismitoad is essentially the resident friendly neighbourhood poor man's Swampert, one of the very few Water Pokémon that does not learn Ice Beam or Blizzard, but still does very well even without them. The only real downside is how long it takes Tympole to evolve; after reaching Palpitoad status, with the help of the Eviolite, its survival should essentially be ensured. The relatively unimpressive Speed can also be boosted by Rain Dance and Swift Swim for those that have it. All in all, a solid and reliable choice for many nuzlockers to have, and probably one of the region's most splashable Water Pokemon.
N (Nacrene City): Be somewhat wary of Pidove's Leer and Quick Attack combination, which may become deadly if Super Luck activates; same for Timburr: if there is anything Tympole should do, that is using Supersonic and attack only if the enemy is already below half health, lest it use Bide and OHKO Tympole. The mirror match with N's Tympole should be easy with Round spam.
Gym #2 - Lenora (Nacrene City, Normal-type): No. Both of Lenora's Pokémon are way too strong for Tympole to handle.
Gym #3 - Burgh (Castelia City, Bug-type): An Eviolite Tympole has a somewhat hard time against Whirlipede due to its bulk, as well as Screech and the high likelihood of poisoning with Poison Tail; it can manage a 3HKO with some luck, however. Dwebble is better, but Leavanny is just unthinkable. An already-evolved Palpitoad will have an easy time against the first two, but still needs to steer clear from the third, even more so with the newly acquired double weakness.
Bianca (Castelia City): Both Tympole and Palpitoad need to stay away from Pansage and Servine, and Tympole specifically will find Herdier very hard to beat, and Dewott too, due to its Fury Cutter damage stacking up. Tympole may also have a hard time against Pignite's Arm Thrust, notwithstanding the Eviolite, but short of two consecutive turns of 4-5 hits, this will not be an issue: BubbleBeam 2HKOs Pignite without problems. The rest can be handled well by both evolutionary stages, with Palpitoad specifically having no real problems against anything but the Grass-types.
Cheren (Route 4): Liepard is too tough for Tympole and has Pursuit, which makes it a way too dangerous opponent, but Palpitoad can tackle it just fine and Tympole could theoretically manage with the Eviolite, but should avoid the matchup unless needed as its Sand-Attack means business. Pidove is not a problem for either evolutionary stage. For the rest, the same observations apply: no Grass-types, avoid Dewott and Pignite as Tympole if possible, the rest is okay for both Tympole and Palpitoad to fight against.
N (Nimbasa City): Everything except Sigilyph is easy for Palpitoad, but do not underestimate Scraggy's Swagger if it is used; a boosted Attack stat with confusion damage, together with Scraggy's own moves, can end a weakened Palpitoad. Sigilyph is hard for almost every single Pokémon in existence at this point, but Palpitoad can wear it down with BubbleBeam, at least until it gets in the critical zone and/or needs healing. The Eviolite will be needed, but it will also make the matchup much easier, as Sigilyph can at best score a 4HKO against an Eviolite Palpitoad, who can 3HKO in return.
Gym #4 - Elesa (Nimbasa City, Electric-type): Spam BubbleBeam against Emolga and Mud Shot against Zebstrika, heal as needed, GG. While we're on the subject, Eviolite Palpitoad is one of the best available answers to Elesa's Zebstrika since it resists Flame Charge and is immune to Volt Switch. Consider yourself lucky if you have it!
Cheren (Route 5): The evolution of Pidove into Tranquill did not significantly change the matchup. Palpitoad can defeat them all just fine, except Pansage and Servine.
Gym #5 - Clay (Driftveil City, Ground-type): Trickier than one would expect. Krokorok will likely Swagger on the first turn, and this is a problem since it is faster than Palpitoad; give Palpitoad a Persim Berry if available, or another item that heals confusion in battle. Palpitoad can then proceed to spam Muddy Water against everything, including Clay's own Palpitoad. However, if the Persim Berry is being held, Palpitoad cannot fight Excadrill in any way, since Clay's ace requires Palpitoad to hold the Eviolite in order to be successful. 72 HP EVs and 80 Defense EVs with a Defense-hindering nature avoid the 2HKO from unboosted Bulldoze, assuming Palpitoad holds Eviolite. If it starts using Hone Claws, a critical Bulldoze would kill Palpitoad from full health, and Muddy Water is only a 2HKO. This 2HKO is guaranteed with no investment if Palpitoad's nature is neutral or better with respect to Special Attack, and requires 64 EVs with a hindering nature.
Bianca (Driftveil City): Munna is now a Musharna, but Palpitoad should still be able to take it on, thanks to the Eviolite. However, this fight can become difficult due to Musharna's special bulk, and Palpitoad's moves being largely special; leave it to something with Dark coverage if available. The rest, apart from the Grass-types, is fine; Palpitoad can defeat everything without much of a problem.
N (Chargestone Cave): Boldore is laughable, and Ferroseed does not have a damaging Grass move, so it is not dangerous. Joltik and Klink are possibly even easier than Boldore, as they do not have Sturdy. STAB spam is the way to win here.
Gym #6 - Skyla (Mistralton City, Flying-type): An Eviolite Palpitoad should outmatch Swoobat and Unfezant, but due to its slowness and their relatively powerful attacks, it may not be able to fight both unless healed; if healing items are in play, Palpitoad will have no problems, as Swoobat can 3HKO at best and Unfezant's moves are even weaker, whereas Palpitoad averages on a 2HKO bordering a 3HKO (2HKO is almost guaranteed against Swoobat with Muddy Water). Swanna is not advised, as it resists BubbleBeam/Muddy Water and is immune to Ground moves; it can also retaliate with STAB Air Slash. Seismitoad will have an easier time against the first two, but lacks substantial responses for Swanna as well; it would be a doable stall fight factoring healing items into the equation, but it will be stall.
Cheren (Route 7): Again, avoid Simisage and Servine. Nothing else is threatening for a Seismitoad, though Unfezant can be annoying with Air Slash and its high critical hit ratio; Muddy Water still outdamages it, though, so only low health Seismitoad will need to watch out for this.
Gym #7 - Brycen (Icirrus City, Ice-type): Do not underestimate Cryogonal's Frost Breath, though Vanillish's is much weaker. Surf can KO all three of Brycen's Pokémon, but Beartic can get annoying with Swagger. However, because it is slower than Seismitoad, the confusion will be easier to work around. Seismitoad should be healed as needed, especially if it is low on health, due to Beartic's Slash. Swagger can even be exploited in Seismitoad's favour after healing: one Surf and one Swagger-boosted Dig will do Beartic in. If Seismitoad needs to fight Cryogonal as well, it should use Return, which is the only move available to Seismitoad that can score a 2HKO; Seismitoad can also set up Rain Dance, which will help Seismitoad outspeed Cryogonal if its ability is Swift Swim.
Bianca (Route 8): Again, do not do the Grass-types. Consider carefully whether or not to fight Stoutland as well; it has a pretty sizable chance of outspeeding Seismitoad, plus it has Work Up and is unlikely to be 2HKOed. Swift Swim Seismitoad have it easier, as they can set up Rain Dance the first turn and then hit Stoutland with Surf until it goes down; Rain-boosted Surf will usually net the 2HKO, but the move would otherwise only 3HKO. Musharna and the non-Grass monkeys are also fine.
Gym #8 - Iris/Drayden (Opelucid City, Dragon-type): Seismitoad sadly gets no Ice coverage whatsoever, which makes this fight difficult. Dig is the best it can do, and it is no weapon against Fraxure and Haxorus, both of which can use the underground turn to set up Dragon Dances; those two should be avoided, since if Seismitoad cannot defeat them, they will become very dangerous. Return 3HKOs Fraxure, which is still not enough to prevent it from wreaking Dragon Dance-based havoc. Druddigon is easier, though still very powerful and not to be underestimated; however, unlike its colleagues, there is no risk in using Dig against it.
Cheren (Route 10): Seismitoad should never fight against the Grass-types, but everything else is good. Keep an eye on Liepard and Unfezant, as they can score cheap crits on a low-health Seismitoad; at any rate, Seismitoad should already have Drain Punch to dispose of Liepard and enough health to shrug off their normal hits. The rest goes down to Surf or Dig, depending on typing.
Elite Four Shauntal (Pokémon League, Ghost-type): Cofagrigus has Grass Knot and Jellicent has Energy Ball, meaning Seismitoad can fight neither. On the upside, Golurk and Chandelure should both be easy, as they are weak to Water. While Surf is a great move to use, bear in mind that if Golurk is not OHKOed by it and lays a Curse on Seismitoad, it needs to switch out before Chandelure comes in, because Chandelure will also live a hit and OHKO back with the residual Curse damage; on average, Shadow Ball deals about 50% to Seismitoad. Swift Swim specimen may benefit from setting up Rain Dance before attacking.
Elite Four Marshal (Pokémon League, Fighting-type): While both Sawk and Conkeldurr have Grass Knot, their Special Attack is also low enough that it can only 3HKO Seismitoad. Still, keep it in mind, especially below half health, where a critical hit can bee lethal. If you can trick the AI into using Grass Knot all the time, this may actually be beneficial for Seismitoad, as all their other moves deal more damage than Grass Knot, even Throh's Storm Throw. Overall, Seismitoad can take on any of Marshal's Pokémon, but will probably be unable to defeat them all, because they are sturdy and one of them actually also has Sturdy (Sawk), so the damage will eventually pile up. If Seismitoad is healed as needed in between battles, it may be able to pull off a sweep, but do not take too many risks. Use caution against Mienshao unless your Seismitoad has Swift Swim and the rain is already up: Surf is only a 2HKO, with or without rain, and the foe's Swords Dance + Jump Kick combo kills Seismitoad from full health.
Elite Four Grimsley (Pokémon League, Dark-type): A good fight for Seismitoad overall, especially the matchup against Krookodile. Surf will work well for it, while Drain Punch takes care of the rest, healing up Seismitoad in the meantime; this is especially advantageous if Liepard or Bisharp come in before Krookodile, as Krookodile is faster than Seismitoad and will deal some damage before going down, while Liepard and Bisharp are perfect occasions to replenish Seismitoad's HP with Drain Punch. Note that the HP replenishing is actually useful, as Seismitoad will take some time to dispose of everything (Scrafty takes three hits to beat, everything else takes two). Your Pokemon will be in no danger, though, since none of their moves can kill even with a critical hit, except Krookodile's Earthquake (and that only with a high damage roll).
Elite Four Caitlin (Pokémon League, Psychic-type): Reuniclus is off limits due to Energy Ball, and do not fight Gothitelle with Seismitoad if you can help it, as it has Calm Mind and will put the entire team in danger with enough setups; Surf and Dig are 3-4HKOs, which is well beyond the danger zone for Gothitelle's Calm Mind. Sigilyph and Musharna are better; Sigilyph can 3HKO but is 2HKOed in return, if Seismitoad uses Surf supported by either Rain Dance (best option for Swift Swim ones) or the Mystic Water. Seismitoad is an especially good candidate to fight Musharna due to its Electric immunity, which prevents it from stacking up Special Attack boosts with Charge Beam.
Reshiram/Zekrom (N's Castle): Seismitoad's resistance to Fusion Flare and immunity to Fusion Bolt make both fights a lot easier than they would be for other Pokémon. Dig is a plain 2HKO against Reshiram, and achieves a certain 2HKO against Zekrom too (if Seismitoad holds the Soft Sand or the Expert Belt). DragonBreath is still fairly strong, especially when used by Reshiram, but only achieves a 3HKO in either case, so Seismitoad is safe.
N (N's Castle): The Tao dragon is more powerful than its wild equivalent, due to having Giga Impact or Hyper Beam, depending on version. Reshiram has Reflect as well, which could be very troublesome since Seismitoad's best asset against it is Dig. Zekrom carries Light Screen instead, but that, too, can be a problem after it goes down, because it nerfs Surf. Dig works well against Klinklang and Carracosta, and for Carracosta, Grass Knot is even better if Seismitoad has it; it has Sturdy though, and it also carries Aqua Jet, which is even more dangerous for a Seismitoad in the red. Archeops will be murdered by Surf, but not without getting an Acrobatics off first; while a regular hit is not a problem for Seismitoad's bulk, a critical will definitely kill, so something faster or with Aqua Jet should be used if available, as it will bring Archeops to Defeatist range. Vanilluxe will generally outdamage Seismitoad, but Seismitoad can make do with Drain Punch or Rain Dance + Surf, both of which also work for Zoroark once it's unmasked.
Ghetsis (N's Castle): Cofagrigus will annoy Seismitoad with Toxic, but is otherwise beatable if healing items can be used at will; Bouffalant is really tough, and its Head Charge is no fun to take, so withdraw any Seismitoad that is not running Drain Punch. Even with Drain Punch, the damage Head Charge deals will OHKO Seismitoad with a critical hit unless its Defense is well above average. The mirror match against Ghetsis' Seismitoad sees yours at a disadvantage: the enemy has access to Earthquake, and yours does not, so it should either leave the enemy Seismitoad to an appropriate teammate or set up Rain Dance if its ability is Swift Swim. In the latter case, Surf will be a 2HKO. Go with Drain Punch against Bisharp, then Surf again for Eelektross, whose Acrobatics is only a 3-4HKO; Surf can either 2HKO or 3HKO depending on whether the rain is up or not. Lastly, Hydreigon is also a Drain Punch candidate, but once again Seismitoad needs to make sure it is in safe conditions to fight it: it will be faster than Seismitoad unless Rain Dance is up and Seismitoad has Swift Swim, and its Dragon Pulse can do up to half Seismitoad's health. If you attempt this matchup, make sure there is a safe switch-out if Seismitoad needs to withdraw, whether the cause is Rain Dance wearing off or something else. Drain Punch will 3HKO it, with a 2HKO chance if Seismitoad holds the Expert Belt.
Post-Game: Just keep Seismitoad far away from Grass coverage as usual, and it will be highly unlikely for any one hit to kill it. It can still hold its own well.
Tympole's initial moveset consists of Growl, Supersonic, Round and BubbleBeam. It also learns Mud Shot at level 16, which is a good coverage move and will gain STAB after it evolves. At level 20, it gets Aqua Ring, which is another good option; the line has mixed stats and fairly good bulk, as well as sporting a single weakness to account for, one that is not commonly seen in Unova. Then, it gets Uproar at level 23, but this move is a double-edged sword: while it is fairly powerful in this generation, it keeps attacking until either all opponents are defeated or the user goes down for a maximum of three turns, and Tympole's frailty needs to be kept into account when using it. After evolution, Palpitoad learns Muddy Water at level 28; this move has good base power, but also imperfect accuracy, and should only be used side by side with BubbleBeam until Surf comes around. At level 33, the line gets Rain Dance, which is very useful; Swift Swim users will outspeed nearly anything with it, and Hydration users can profit of Rest and Leftovers to run a defensive set. However, Hydration users should keep in mind that upon evolving into Seismitoad, the ability will change into Poison Touch. Seismitoad learns Acid upon evolution, at level 36, but it is not really a move worth keeping; then, it gets Flail at level 39, but that move is pretty useless compared to the alternative options. Drain Punch, learned at level 44, is a very good option for recovery sets, and can work well for general coverage purposes on offensive sets. There is not much else to Seismitoad's natural moveset; it gets Echoed Voice at level 49, which is beyond useless, and then Hydro Pump at level 53, but Surf is generally better, thanks to its significantly higher accuracy. If Seismitoad ever gets there, it will also learn Hyper Voice at level 59, but again, this is not a move worth Seismitoad's last slot unless it's Modest or some similar circumstance is in play.
Seismitoad's TM movepool is very vast. Naturally, it gets Surf, its most reliable Water-type move; Scald also becomes an option later down the road, advised for defensive sets, as the burn chance can be useful to tank physical hits better. Sadly, its best Ground STAB available is Dig, as Earthquake is a postgame TM. Other coverage moves come in the form of Rock Slide, always a solid choice, or Grass Knot, though not usually all that great when there is already a solid Water STAB move available. Focus Blast is an option for those who prefer power over accuracy, and/or have a specially oriented Seismitoad and prefer to not run Drain Punch. There is also a multitude of Poison moves available, from Sludge Wave to Poison Jab, but Seismitoad is unlikely to need Poison moves; Toxic is another story, and would work well with defensive sets. Interestingly, Seismitoad is one of the few Water-types that cannot learn Ice Beam or Blizzard, though with its readily available coverage this will hardly ever be an issue.
Pokémon that are good against Grass-types: Seismitoad has only one weakness, which is very easily covered for, since Grass-types have many weaknesses and can be hit for super effective damage by countless other types. Additionally, many common Pokemon in Unova counter Grass types.
Fast hitters: While Seismitoad's Speed is not bad, there are several enemies in the game that a Seismitoad without Swift Swim simply cannot expect to hit first. Poison Touch users should be backed by a glass cannon or other similar fast damage dealer, in the event that Speed becomes mission critical in a matchup.
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.
Tympole Line Ratings
What Nature do I want? As Seismitoad's best sets are usually mixed, neither Attack nor Special Attack should be lowered, especially Attack. The best option may actually be a Speed-lowering nature, especially for Swift Swim users, who will not find it hard to compensate for that drop with Rain Dance. Brave should work best, but natures such as Quiet, Relaxed and Sassy will also do.
Which Ability do I want? Swift Swim. Hydration is only useful for as long as Tympole is not fully evolved, and Poison Touch is both underwhelming and unreliable, even if Seismitoad runs Venoshock.
At what point in the game should I be evolved? A Palpitoad will be needed before Elesa, and it should then be evolved into Seismitoad before fighting Skyla. In general terms, Tympole should be evolved as soon as possible because it is frail, but there is no particular hurry reaching Seismitoad status; just do not evolve it too late or Seismitoad will miss out on Drain Punch.
How good is the Tympole line in a Nuzlocke? Pretty good, despite the lack of specialisation and Earthquake being a postgame move. It can deal considerable damage, takes hits well, and has a wide enough movepool to not fall short against anything but Grass-types, the only things that give it trouble.
Tympole's type matchups:
Weaknesses: Grass, Electric
Resistances: Steel, Fire, Water, Ice
Neutralities: Normal, Fighting, Flying, Poison, Ground, Rock, Bug, Ghost, Psychic, Dragon, Dark