Gengar-Mega @ Choice Specs / Choice Scarf
Ability: Beads of Ruin  
Tera Type: Ghost  
EVs: 252 HP / 252 Def / 252 SpA / 252 SpD / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Moongeist Beam  
- Astral Barrage / Fleur Cannon
- Sludge Bomb / Fleur Cannon
- Volt Switch

Diancie-Mega @ Choice Specs  
Ability: Pixilate  
Tera Type: Rock  
EVs: 252 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe  
Rash / Naive Nature  
- Boomburst  
- Earth Power  
- Extreme Speed  
- Volt Switch