A probably bad m-diancie team

Diancie-Mega @ Diancite
Ability: Magic Bounce
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Calm Mind
- Moonblast
- Power Gem
- Earth Power

Celesteela @ Leftovers
Ability: Beast Boost
EVs: 248 HP / 8 Def / 252 SpD
Sassy Nature
- Leech Seed
- Heavy Slam
- Flamethrower
- Protect

Kyurem-Black @ Expert Belt
Ability: Teravolt
EVs: 4 Atk / 252 SpA / 252 Spe
Naive Nature
- Ice Beam
- Earth Power
- Fusion Bolt
- Hidden Power [Fire]

Landorus-Therian @ Flyinium Z
Ability: Intimidate
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Swords Dance
- Earthquake
- Fly
- Stealth Rock

Latias @ Soul Dew
Ability: Levitate
EVs: 248 HP / 8 Def / 252 Spe
Timid Nature
IVs: 0 Atk
- Draco Meteor
- Psyshock
- Defog
- Healing Wish

Clefable @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
IVs: 0 Atk
- Moonblast
- Soft-Boiled
- Stealth Rock
- Thunder Wave

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A M-Diancie team for OU, taking advantage of diancie getting power gem and the auto speed boost to use a calm mind set. e-belt hp fire kyurem to take care of the annoying defensive cores + threaten scizor a bit more because this team is relatively weak to it, latios for defog + healing wish (feel free to change the EVs on this if you want), and dual stealth rock because I'm bad (feel free to substitute stealth rock on lando-t for smack down/gravity since otherwise you're hard walled by celesteela). Also gren can really mess this team up, as the check is basically spdef cele and clef if it doesn't have gunk shot.