Probably not very good 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