Mewtwo-Mega-Y @ Choice Specs  
Ability: Psychic Surge  
EVs: 252 HP / 252 Def / 252 SpA / 252 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Psycho Boost  
- Psystrike  
- Moongeist Beam  
- Volt Switch  

Tyranitar-Mega (M) @ Choice Band  
Ability: Tough Claws
EVs: 252 HP / 252 Atk / 252 Def / 252 SpD / 252 Spe  
Adamant Nature  
- Knock Off  
- Pursuit  
- U-turn  
- Switcheroo  

Giratina @ Toxic Orb  
Ability: Poison Heal  
EVs: 252 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD  
Relaxed Nature  
IVs: 0 Spe  
- Core Enforcer  
- Wish  
- Spiky Shield  
- U-turn  

Diancie-Mega @ Pixie Plate  
Ability: Pixilate  
EVs: 252 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe  
Hasty Nature  
- Fake Out  
- Extreme Speed  
- Boomburst  
- Stealth Rock  

Groudon @ Rocky Helmet  
Ability: Soundproof  
EVs: 252 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD  
Relaxed Nature  
IVs: 0 Spe  
- Thousand Waves  
- Parting Shot  
- Milk Drink  
- Defog  

Chansey @ Choice Scarf  
Ability: Imposter  
EVs: 252 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD  
Relaxed Nature  
IVs: 0 Spe  
- Metal Burst  
- Whirlwind  
- Soft-Boiled  
- Trick