
Gardevoir @ Gardevoirite
Ability: Trace - Pixilate
Nature: Timid
EVs: 252 SpA / 252 Spe / 4 SpD
-Hyper Voice
-Psyshock
-Focus Blast
-Shadow Ball
I built this team around Mega Gardevoir because it is just so amazing. Its stats are to die for, it has a great ability, and it has good coverage. Anyway, down to business. Gardevoir's role is covering for Bisharpp and being an insanely powerful sweeper. Gardevoir is very dangerous with Tailwind support from Talonflame. Hyper Voice for powerful Fairy STAB, Psyshock to hit specially defensive walls, Focus Blast for steels, and Shadow Ball because this set is walled by Psychic types otherwise. Gardevoirite obviously because that's what Gardevoir needs to be mega.

Rotom-Wash @ Leftovers
Ability: Levitate
Nature: Calm
EVs: 252 HP / 126 SpD / 126 Def
-Hydro Pump
-Volt Switch
-Will-o-Wisp
-Pain Split
Rotom-Wash is on this team because I need a wall, and Rotom is a great one. It also 4x resists steel-types that really hurt Gardevoir. Rotom's role is switching in on basically every attack that I don't want something else taking and crippling physical attackers. It can also give me momentum with Volt Switch. I run Hydro Pump because it is decently powerful and it is the only good water-type STAB that Rotom gets. Volt Switch is electric STAB and momentum, and Will-o-Wisp destroys physical attackers that trouble Gardevoir. Finally, Pain Split to get health back. Leftovers is great for recovery.

Talonflame @ Life Orb
Ability: Gale Wings
Nature: Adamant
EVs: 252 Spe / 252 Atk / 4 Def
-Brave Bird
-Flare Blitz
-U-turn
-Tailwind
I put Talonflame on this team because it is a great physical attacker and priority Brave Bird is just too strong. Talonflame's roles on this team are cleaning up late-game, setting up Tailwind, and scouting. I put on Brave Bird because it is the best move ever with Gale Wings. Flare Blitz is there for powerful fire-type STAB and to take care of steel-types that scare Mega Gardevoir. U-turn is good for scouting. Lastly, Tailwind is good because Mega Gardevoir is not really that fast. Life Orb is good for a little extra damage.

Bisharp @ BlackGlasses
Ability: Defiant
Nature: Adamant
EVs: 252 Atk / 252 Spe / 4 Def
-Knock Off
-Iron Head
-Sucker Punch
-Pursuit
Bishop is on this team because he provides Pursuit support for Gardevoir and I needed a Steel type. His role on the team is providing support with Pursuit and Knock Off. My team can also cover for his Fighting type weakness really well. As said before, he has Pursuit for the Ghost types that are problems for Gardevoir. Knock Off is great for removing items and Sucker Punch is great priority. Finally, Iron Head takes care of any Fairies. BlackGlasses is my item because Bisharp has three dark type moves.

Haxorus @ Lum Berry
Ability: Mold Breaker
Nature: Jolly
EVs: 252 Atk / 252 Spe / 4 Def
-Dragon Dance
-Outrage
-Poison Jab
-Earthquake
I decided to use Haxorus because I needed a Dragon type and I love it's huge Attack stat. It's uncommon typing is very manageable, and it's speed is great with Tailwind support. Its role is Setup Sweeper and overall physical threat. Dragon Dance is a fantastic setup move, and at +1 or +2, Outrage destroys everything. Poison Jab is there for Fairies and because Togekiss walls my set otherwise. Last but not least, Earthquake combined with Mold Breaker is just too good. I run Lum Berry because everyone likes statusing Haxorus.

Lucario @ Focus Sash
Ability: Steadfast
Nature: Timid
EVs: 252 SpA / 252 Spe / 4 Def
-Nasty Plot
-Vacuum Wave
-Flash Cannon
-Aura Sphere
Finally, Lucario. I chose Lucario for this team because it 4x resists Rock, which is a problem for Talonflame. It's role is a special setup sweeper and a hard counter for Rock types. He also has some nice fighting priority. Nasty Plot for nasty setup and Vacuum Wave for priority. Finally, Flash Cannon and Aura Sphere for powerful STAB. Focus Sash is my favorite item for this set because it guarantees that Lucario set up at least one Nasty Plot and it helps with it's very low defenses.
Thanks for reading!