Basic Overview
I see this is a Groudon + Rayquaza core with Gengar, Froslass, Crobat as support and Metagross as the Mega. Although this core is used rarely, I can see it working. Firstly, I'll review each Pokémon.
Groudon
All seems fine, but replacing Stone Edge with Rock Slide will help out a lot, as Stone Edge's accuracy is quite poor.
Rayquaza
This is a mixed Rayquaza, which is viable but not the very best like no-one ever was . As Rayquaza has Air Lock, having a Water type move (Waterfall) can br used to defeat other Groudon. Even Surf is a good option. Currently I see no problem with this Rayquaza though.
Metagross
An interesting choice, Metagross is. Although it has high power and ability to counter Xerneas, Mawile fills that spot better and isn't allergic to Knock Off.
Mawile @ Mawilite
Nature: Jolly (+Spe, -Sp.Atk)
EVs: 252 Spe / 252 Att / 4 HP
Ability: Intimidate ---> Huge Power
- Protect
- Sucker Punch
- Play Rough
- Iron Head
This counters the heck out of Xerneas. Using Sucker Punch is for quick revenge kills, while Play Rough + Iron Head nukes everything but Groudon. This set assumes Tailwind is up, and can even outspeed Ylvetal.
Crobat
Having used this very Pokemon, let me tell you that you do not want Cross Poison. Crobat's job lies in halving the HP of bulky Pokémon, setting up Tailwind etc. However you do not have Taunt on your Crobat, which is essential at stopping Xerneas that are Geomancing, and move the 8 EVs back to HP, and replace Jolly with Timid, to lessen the power of Foul Play. Use a Lum Berry instead of a Mental Herb, so you can shut down Smeargle.
Froslass
I see Froslass as mainly a niche option. Although it looks good on paper, it loses to the two primals and is terribly allergic to Knock Off. I would suggest Weavile instead.
Weavile @ Focus Sash
Ability: Pressure
EVs: 252 Spe / 252 Att / 4 SPD
Nature: Jolly (+Spe, -SpAtk)
- Knock Off
- Icicle Crash
- Feint
- Fake Out
Simple but effective. Fake Out to help an ally set up, and to break Focus Sash's. Feint is used for Protect predictions, and for a quick move to revenge kill. Icicle Crash + Knock Off are STAB.
Gengar
You seem to have built a quick sweeper with Gengar, although you have a Sitrus Berry as the item. I would recommend changing the moveset to:
- Will-O-Wisp
- Protect
- Sludge Bomb
- Icy Wind
This allows you to decrease an opponent's speed, further helping with your Speed based team. Will-O-Wisp physical attackers and Sludge Bomb the world.
Hope I helped!
