Diancie @ Weakness Policy  
Ability: Clear Body  
Tera Type: Rock  
EVs: 248 HP / 44 Atk / 92 Def / 124 SpD  
Sassy Nature  
IVs: 0 Spe  
- Diamond Storm  
- Play Rough  
- Trick Room  
- Encore  

Volcanion @ Choice Specs  
Ability: Water Absorb  
Tera Type: Fire  
EVs: 248 HP / 108 Def / 128 SpA / 16 SpD / 8 Spe  
Modest Nature  
IVs: 0 Atk  
- Steam Eruption  
- Overheat  
- Sludge Wave  
- Hyper Beam  

Cresselia (F) @ Covert Cloak  
Ability: Levitate  
Tera Type: Psychic  
EVs: 248 HP / 84 Def / 176 Spe  
Bold Nature  
IVs: 0 Atk  
- Calm Mind  
- Psychic  
- Icy Wind  
- Moonlight  

comp spdef diancie and comp specs volcanion, the cress is cloak so i cant get haxed by pecha and it works to beat garchomp too w icy wind