I've always been fond of rain teams, and after seeing that Carson Confer won the Latin American International Championships with one, I decided to give rain another try.

Ludicolo @ Waterium Z
Ability: Swift Swim
Level: 50
EVs: 4 HP / 252 SpA / 252 Spe
Modest Nature
- Hydro Pump
- Energy Ball
- Ice Beam
- Fake Out

Pretty standard Ludicolo. Hydro Vortex in the rain is insanely powerful.

Politoed @ Eject Button
Ability: Drizzle
Level: 50
EVs: 252 HP / 228 Def / 28 SpD
Sassy Nature
IVs: 0 Atk / 0 Spe
- Scald
- Helping Hand
- Encore
- Protect

Utility Politoed. Its main goal is bringing in the rain, but it can do other things like Encore a Fake Out or a status move, or power up a partner's attack with Helping Hand. I'm on the fence about the Eject Button... it has been both helpful and harmful at times. I'm not sure what the EVs do, but Carson used Sassy with this moveset, and this is the most commonly used Sassy spread on Pikalytics.

Landorus-Therian @ Assault Vest

Ability: Intimidate
Level: 50
EVs: 244 HP / 12 SpD / 252 Spe
Adamant Nature
- Earthquake
- Rock Slide
- Knock Off
- U-turn

Basic physical Landorus-T. Carson used a special Landorus-T on his team, but I went with a physical variant instead since I needed more physical offense on my team. EVs are from Wolfe's guide to Landorus-T on YouTube.

Gengar-Mega @ Gengarite
Ability: Cursed Body
Level: 50
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Sludge Bomb
- Shadow Ball
- Icy Wind
- Protect

Pretty standard Gengar. Max Speed to at worst tie with Tapu Koko. I don't use Icy Wind much and am thinking of dropping it for something else, such as Substitute. My thought process behind Gengar was to trap opposing weather-setters and deal with them so they cannot switch in and out, but it's so frail that I'm not sure if it's worth keeping.

Celesteela @ Leftovers
Ability: Beast Boost
Level: 50
EVs: 252 HP / 164 Def / 92 SpD
Sassy Nature
- Heavy Slam
- Flamethrower
- Leech Seed
- Protect

Rain lessens Celesteela's Fire weakness. I originally had Ferrothorn in this slot, who I had success with in rain teams in past years, but Celesteela brings Flamethrower for Scizor, Ferrothorn, and Kartana. If needed, I should be able to stall out the rain in order to use it. EVs are made to make defenses nearly equal but give Special Defense a boost with Beast Boost. I'm not sure if that's what I want or not.

Tyranitar @ Weakness Policy
Ability: Unnerve
Level: 50
EVs: 252 HP / 252 Atk / 4 Spe
Adamant Nature
- Rock Slide
- Crunch
- Low Kick
- Protect

Tyranitar is here to counter some Pokémon that my team has trouble with, namely Zapdos and Charizard (if I don't have rain up). I chose Unnerve over Sand Stream to not interfere with my rain, but I'm considering going with Sand Stream since sand doesn't hurt half my team, it overwrites Drought, and it buffs Tyranitar's Special Defense. I'm sure there's probably a better EV spread I could use.