Mega Altaria team by Frubblez

Altaria-Mega @ Altarianite
Ability: Natural Cure
EVs: 252 HP / 4 SpA / 252 SpD
Calm Nature
IVs: 0 Atk
- Moonblast/Hyper Voice
- Flamethrower
- Roost
- Cotton Guard

Dugtrio @ Groundium Z
Ability: Arena Trap
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Earthquake
- Substitute
- Toxic
- Screech

Keldeo-Resolute @ Choice Specs
Ability: Justified
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Hydro Pump
- Secret Sword
- Icy Wind
- Scald

Magearna @ Assault Vest
Ability: Soul-Heart
EVs: 200 HP / 56 SpA / 252 SpD
Calm Nature
- Fleur Cannon
- Flash Cannon
- Hidden Power [Fire]
- Volt Switch

Marowak-Alola @ Thick Club
Ability: Lightning Rod
EVs: 252 Atk / 4 Def / 252 Spe
Adamant Nature
- Fire Punch
- Shadow Bone
- Stealth Rock
- Swords Dance

Latios (M) @ Choice Scarf
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Draco Meteor
- Psyshock
- Energy Ball/Trick
- Defog