Mega Dos

Gyarados @ Gyaradosite
Ability: Intimidate
EVs: 100 HP / 252 Atk / 156 Spe
Adamant Nature
- Substitute
- Dragon Dance
- Earthquake
- Waterfall

Raikou @ Assault Vest
Ability: Pressure
Shiny: Yes
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Thunderbolt
- Volt Switch
- Shadow Ball
- Hidden Power [Ice]

Clefable @ Leftovers
Ability: Magic Guard
EVs: 248 HP / 252 Def / 8 Spe
Bold Nature
- Calm Mind
- Moonblast
- Flamethrower
- Soft-Boiled

Landorus-Therian @ Leftovers
Ability: Intimidate
EVs: 252 HP / 220 Def / 36 SpD
Impish Nature
- Stealth Rock
- Earthquake
- Stone Edge
- Knock Off

Latios @ Choice Scarf
Ability: Levitate
EVs: 4 HP / 252 SpA / 252 Spe
Timid Nature
IVs: null Atk
- Psyshock
- Draco Meteor
- Energy Ball
- Defog

Keldeo-Resolute @ Choice Specs
Ability: Justified
Shiny: Yes
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Hydro Pump
- Secret Sword
- Scald
- Hidden Power [Electric]