[ORAS] Need help filling the last 2 slots for my Generation Showdown team.

[AttilatheFun87]

So I decided to plan out my team for the Generation Showdown competition that was announced for next month so I could have it all ready to go. I was hoping for suggestions of what to to fill in the remaining slots of my team with. Any other suggestions are appreciated. Yeah I know mega rayquaza is broke, but this will likely the only time I ever use him.

Rayquaza-Mega @ Life Orb
Ability: Delta Stream
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Extreme Speed
- Outrage
- Dragon Ascent
- Iron Head

Xerneas @ Power Herb
Ability: Fairy Aura
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Moonblast
- Flash Cannon
- Psyshock
- Geomancy

Landorus-Therian (M) @ Choice Band
Ability: Intimidate
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Earthquake
- Rock Slide
- Knock Off
- U-turn

Gengar @ Focus Sash
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Sludge Bomb
- Shadow Ball
- Dazzling Gleam
- Destiny Bond