Your (Diancie-Mega) @ Choice Specs  
Ability: Pixilate  
EVs: 252 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe  
Naive Nature  
- Boomburst  
- Blue Flare  
- Extreme Speed  
- Steam Eruption  

Spirit (Arceus-Poison) @ Earth Plate  
Ability: Ice Scales  
EVs: 252 HP / 252 Def / 252 SpA / 252 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Judgment  
- Thunder Cage  
- Take Heart  
- Strength Sap  

And (Groudon-Primal) @ Assault Vest  
Ability: Regenerator  
EVs: 252 HP / 252 Atk / 252 Def / 252 SpD  
Sassy Nature  
IVs: 0 Spe  
- Precipice Blades  
- Fire Lash  
- U-turn  
- Mortal Spin  

My voice (Celesteela) @ Covert Cloak  
Ability: Primordial Sea  
EVs: 252 HP / 252 Atk / 252 Def / 252 SpD  
Relaxed Nature  
IVs: 0 Spe  
- Stone Axe  
- Flip Turn  
- Sticky Web  
- Shore Up  

In one (Palkia-Origin) @ Ability Shield  
Ability: Fur Coat  
EVs: 252 HP / 252 Def / 252 SpA / 252 SpD / 252 Spe  
Timid Nature  
- Scald  
- Knock Off  
- Heal Bell  
- Recover  

Combined (Flutter Mane) @ Life Orb  
Ability: Magic Guard  
EVs: 252 HP / 252 Def / 252 SpA / 252 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Astral Barrage  
- Moonblast  
- Pain Split  
- Topsy-Turvy