For a rain team, look for abilities and moves that benefit from rain.
Some things:
- The Swift Swim ability. Doubles their speed in the rain. Includes Pokemon like Ludicolo, Basculegion, Overqwil, and Beartic (with the hidden ability). Tends to be the team's heavy hitter.
- Hurricane. Jumps up to 100% accuracy (from 70%) in the rain. Hits Grass types that might trouble a Water-heavy team otherwise. Already has that with Pelipper. Could take on someone like Dragonite too.
- Thunder. Same as Hurricane. Deals with other Water types well, on top of better coverage. Finds plenty of Pokemon with this. Mentions Raichu as one Pokemon with Lightning Rod (but not the only one) to keep your Water types safer from Electric moves. Could also switch in someone with a Volt Absorb (Lanturn, Jolteon, Kilowattrel) or Motor Drive ability if you expect something to fry Pelipper.
- Thundurus, Tornadus, and Landorus. Carries a move each that increases to full accuracy in the rain.
Consider having the means to set up rain without Pelipper too. Might lose rain because of an enemy weather Pokemon (like Torkoal, Tyranitar, Hippowdon, Abomasnow...). Do not forget about abilities like Cloud Nine (Golduck, Altaria) that suspend weather effects while on the field either.
Finds several more Pokemon in Blueberry Academy that fit pretty well on a rain team too. Leaves you to discover them.
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For a monograss team[ What are you weak to? Fire, Bug, Flying, Ice, and Poison. What Pokemon have a secondary typing to help with that? (Typically only wants dual-typed Pokemon here. Needs to bring a lot to the team to justify a pure Grass type.)
Some options:
- Ludicolo and Sinistcha (with its hidden ability, Heatproof). Helps versus Fire types.
- Toedscruel and Torterra. Beats Poison types. Delivers good damage against Fire types too.
- Ogerpon. Very adaptable with its masks. Depends if you want to use a legendary or not.
- Breloom, Chesnaught, Hisuian Decidueye, Hisuian Lilligant: Fighting for those Ice types. Helps versus Bugs...kinda.
- Arboliva: Free Grassy Terrain.
- Scovillian: Handy versus Bugs and Ice with its Fire typing.
- Rotom (Mow) and Hisuian Electrode: Electric for those pesky Flying types.
- Meowscarada: Does it help versus the above types? ...No. Works against a few different types, though, and is fairly strong for its typing.
Mentions one more thing: sun. Gave Grass types quite a few abilities beneficial in the sun. Names Chlorophyll in particular. Doubles your speed, much like Swift Swim. Must set that manually, however. Provides an additional benefit of instant Solar Beams and Solar Blades. Falls to you if you wish to pursue it.
Two good Chlorophyll Pokemon for the team:
- Victreebel: Solar Beam and Weather Ball. Brings Poison to boot.
- Scovillian: Solar Beam and already strong Fire moves.
Would personally forego the Chlorophyll option on a singles monograss team. Hates using weather manually, especially in singles.
Do not be afraid to go slow. Use your status moves (like Spore and Sleep Powder) to let your Pokemon buff themselves up with moves like Swords Dance, Bulk Up, Dragon Dance, Nasty Plot, Calm Mind, Victory Dance (on Hisuian Lilligant), and so on. Consider something like Leech Seed paired with Eerie Impulse/Charm as an alternative means of doing so. Brings up Strength Sap as another stellar move towards that same end. Recommends at least one fast, hard-hitting Pokemon with some power in case you need it, however, such as Meowscarada.
Personally picks a team of something like Meowscarada, Ludicolo, Breloom, Rotom (Mow), Torterra, and Lilligant. May notice Lilligant is a pure Grass type and not listed above. One reason: Quiver Dance. Becomes a big, fast threat on the special side with enough time.
Pre-post edit: Oh, right. Hydrapple. That over Torterra. Does not need two double Ice weaknesses. Also remembered Hisuian Lilligant's amazing Victory Dance move. Think about that one too.
Edit: Mentioned a Pokemon that returned in Blueberry Academy. Removed it.