Serperior on grassy terrain breaks everything

Serperior @ Choice Specs
Ability: Contrary
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Leaf Storm
- Hidden Power [Fire]
- Glare
- Defog

Tapu Bulu @ Terrain Extender
Ability: Grassy Surge
EVs: 248 HP / 64 Atk / 124 Def / 72 SpD
Adamant Nature
- Horn Leech
- Leech Seed
- Substitute
- Nature's Madness

Tapu Koko @ Light Clay
Ability: Electric Surge
EVs: 56 HP / 200 SpA / 252 Spe
Timid Nature
IVs: 0 Atk
- Reflect
- Volt Switch
- Hidden Power [Ice]
- Light Screen

Hawlucha @ Electric Seed
Ability: Unburden
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Roost
- Swords Dance
- Acrobatics
- High Jump Kick

Magearna @ Assault Vest
Ability: Soul-Heart
EVs: 248 HP / 8 Def / 252 SpD
Modest Nature
- Fleur Cannon
- Hidden Power [Fire]
- Iron Head
- Volt Switch

Landorus-Therian @ Yache Berry
Ability: Intimidate
EVs: 248 HP / 160 Atk / 100 Spe
Adamant Nature
- Earthquake
- Explosion
- Stealth Rock
- Stone Edge