Mega Delphox + Vivillon Balance

Delphox is the star of the team. It is extremely fast, able to outspeed Mega Aerodactyl and Mega Gengar. It always survives Power Gem from Modest Glimmora, as well as a Rock Slide from Jolly Mega Aerodactyl. Try to keep Delphox safe as much as possible to take advantage of its speed and power. Watch out for physical attacks especially as Delphox has poor physical bulk. Delphox can be a powerful late game sweeper or burst damage lead, and matches well into Charizard Y, Floette, Sneasler, Froslass, Venusaur, and Mega Gengar. Watch out for Kingambit, who always OHKOs with Sucker Punch, Garchomp, especially with Choice Scarf, Incineroar, and Tyranatar.

Floette matches well into the Dark types that Delphox does not enjoy going up against. This set has Calm Mind but does not need to set up to do massive damage with Moonblast and Dazzling Gleam. Floette matches well into rain teams as well, threatening Sableye and Archaludon with a lot of damage. Rain teams often don't have a Fairy resist, so with support Floette can often sweep them on its own.

The role of this support Pokémon is to protect its partners, especially Delphox and Floette. Being able to redirect Sucker Punches from Delphox and Dire Claws from Floette can give them a chance to sweep. Additionally, Vivillon can put slower foes to sleep with Sleep Powder, such as Incineroar, Kingambit, and Modest Charizard Y. This is extremely potent against many Trick Room teams, as putting their setter to sleep often will cripple their game plan on Turn 1. Vivillon hates Rock Slides and is often slower than Garchomp. It is also vulnerable to Fake Out breaking its Focus Sash, which it needs in order to make up for its extreme frailty.

With its many strong resistances and great offensive prowess, Garchomp is able to help with defensive pivoting as well as hitting Earthquakes next to Delphox or Vivillon. It is great into Charizard Y and Aerodactyl, but hates going up against Alolan Ninetales, Froslass, and Floette.

Black Glasses Sucker Punch hurts. A lot. Kingambit pressures low HP opponents and can OHKO Fairies like Sylveon and Floette. It underspeeds Sylveon, Sinistcha, and Farigiraf in Trick Room. It also is a great answer to Aerodactyl and Basculegion.

Aegislash is really strong defensively, able to wall Pokémon like Aerodactyl and Sneasler. Spell Tag Shadow Sneak can finish off low HP targets, and Poltergeist deals massive damage to any target that doesn't resist. It is terrible against Kingambit though, as King's Shield will only raise its attack. It functions as a strong defensive switch-in and priority option.