The Team
Diancie-Mega @ Diancite
Ability: Magic Bounce
EVs: 252 SpA / 4 SpD / 252 Spe
Hasty Nature
- Protect
- Moonblast
- Diamond Storm
- Earth Power
Mega Diancie is the first member of the team, and its role is to function as a lead, as a wallbreaker and as support for Volcarona. Not being the stealth rocker means that Diancie doesn't have to take any hits to set up rocks, increasing its longevity so that the threat of magic bounce is there longer. Having both earth power and diamond storm is also nice, because you can reveal one and make the opponent think you don't have the other so that later you can take out a Heatran or Tornadus or something.
Landorus-Therian (M) @ Choice Scarf
Ability: Intimidate
EVs: 232 Atk / 68 Def / 208 Spe
Jolly Nature
- Earthquake
- U-turn
- Explosion
- Defog
Landorus is the scarfer and defogger. With defog on this and magic bounce on Diancie, it's almost always possible to bring Volcarona in with no rocks. Landorus is also pretty much my only check to physical attackers, which is not ideal because it gets worn down pretty easily. I've got explosion over stone edge or whatever else so that I can make scary things go away, but that means the only way it can touch Rotom is by killing itself. Stone edge might be better, I'm not sure.
Greninja-Ash (M) @ Choice Specs
Ability: Battle Bond
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Hydro Pump
- Dark Pulse
- Water Shuriken
- U-turn
Ash Gren is probably my favorite pokemon in OU, and it seems like I can't make any team without putting it on there. The specific reason this one is here is because Volcarona sets up on most of its checks. That's why it has U-Turn, so that if a Ferrothorn or Magearna or something switches into it Volc can just come in immediately and win. Spikes might still be better though, let me know what you think. Other than that, Greninja acts as a wallbreaker and a secondary win condition, and it has the only form of priority on the team.
Volcarona @ Psychium Z
Ability: Flame Body
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Quiver Dance
- Fire Blast
- Psychic
- Hidden Power [Ground]
Finally we reach Volcarona, the mon this team is built around. Volc has psychium z so that it can get past Toxapex or do a strong neutral hit on somebody; the lack of a bug move isn't a huge problem because Tyranitar and the Latis are countered by most of the rest of the team. Surprisingly, this set can actually do pretty well against rain: bring it in while rain isn't up, quiver on the switch to Pelliper and then again on scald/hurricane (it doesn't do that much). Now you're faster than all the swift swimmers, and you can kill Pelliper with your z and get some big damage on whatever comes in next.
Keldeo @ Leftovers
Ability: Justified
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Calm Mind
- Scald
- Secret Sword
- Taunt
Keldeo is the stall/balance breaker, and it fits in surprisingly well with the rest of the team. Having both it and Ferrothorn means that opposing Ash-Gren is almost never a problem, and having both it and Ash-Gren gives this team a pretty okay matchup against rain. It's also an extra fire resist, taking hits from Heatran so that Diancie and Greninja don't have to. One thing I don't like about this set, though, is that going for a calm mind is almost never a good idea, even against stall. Sometimes it works out, but usually I just have a useless move slot.
Ferrothorn @ Leftovers
Ability: Iron Barbs
EVs: 252 HP / 24 Def / 232 SpD
Careful Nature
- Stealth Rock
- Leech Seed
- Power Whip
- Knock Off
Ferrothorn is the rocker of the team and a check to special attackers. It also has power whip, the only move on the team that's super effective against water types, which is not ideal; having a faster threat to mons like Tapu Fini and Mega Swampert would be better. Having another, faster mon with knockoff would also be nice. Even so, I'd say it does its job pretty well; it gets up rocks reliably (so that Diancie doesn't have to), heals up itself and its teammates with leech seed, and also has fairly strong attacks so that it isn't completely passive.
Threats
Tapu Fini - Tapu Fini is the main mon that this team struggles with. Our only super effective hit on it is Ferrothorn's power whip, which is almost impossible to actually use on it if your opponent isn't an idiot. Usually the best way to get rid of it is to get Volcarona to +2 and then OHKO it with z-psychic, but that's kind of hard to pull off.
Celesteela - The only way to really kill this thing is to fire blast it with Volcarona, which means that Volc might get worn down trying to do that. Volc can't usually set up on it either, because of leech seed and protect.
Hawlucha - This pokemon isn't impossible to deal with, but it can be a real problem if you can't outplay your opponent. Lucha + Lele is especially difficult because the spdef boost lets Lucha survive water shurikens that it otherwise wouldn't be able to, and then if your Landorus isn't healthy enough to survive an acrobatics and explode you're basically screwed.
Mold breaker Excadrill - Diancie can't stop this mon from setting up rocks, so sweeping with Volc is a lot more difficult.
Rain - There are some things about this team that make the rain matchup not nearly as bad as it could be (Ferrothorn, double water types, z-psychic on Volc) but the fact that Volc can't operate at full capacity makes it still kind of difficult.
Replays
I thought I knew how to save replays but I guess I didn't. I have a bunch of replays that I downloaded as html files, but I'm not sure how to put them in here. Here's the one replay that I can link to:
https://replay.pokemonshowdown.com/gen7ou-971512758
Pokepaste
https://pokepast.es/0e1a27c6409567a8