Dragapult: With its blistering speed and prodigious attack, Dragapult is the physical wallbreaker. It can hit hard with moves like Phantom Force, Outrage, and Dragon Darts, boost its attack and speed even more with Dragon Dance, or use Sucker Punch to kill an unsuspecting foe.
Gengar: On the special side of things, Gengar cleans up nicely. Its Ghost-Poison typing allows it to pressure Fairies to switch out or force a trade. Sludge Wave, Shadow Ball, and Dazzling Gleam put pressure on opposing Fairies, other Ghosts, and Dark types, respectively, which would pose a huge threat if not taken care of. Focus Blast is there for more Dark coverage, and to scare away/force out Ice, Steel, and Rock types. Choice Scarf allows it to outspeed any unboosted Pokemon not in terrain.
Aegislash: It's kind of the utility guy on this team, but not in a normal way. See, what this team lacks is a reliable defensive backbone alongside G-Corsola. Sure, Polteageist can come in, but to have any offensive presence, it would have to either use Shell Smash or Poltergeist everything. Aegislash fills that role, while also, after a couple of Swords Dances/Weakness Policy activation, can be a fearsome physical attacker with Shadow Sneak and Iron Head for Fairy coverage/Close Combat for Steel coverage. King's Shield is good to change between Sword and Shield Forme, for offense or defense respectively.
Spectrier: It's basically the sample set of Spectrier: Grim Neigh is too OP if you get a few kills, Calm Mind boosts 130 BP Hex after Will-O-Wisp from G-Corsola. Shadow Ball is for when G-Corsola can't burn too many and/or you just need the extra BP. If you really need the extra power, I suggest going Specs + Shadow Ball + Grim Neigh for a good combo. However, Spectrier's poor coverage can leave it walled by Normal-types and Dark-types.
Polteageist: If the team needs some emergency offense, Polteageist can be a late game wincon with Shell Smash, Stored Power, and Poltergeist. If it gets low, you can use Strength Sap to restore a lot of HP and weaken physical Dark types.
Galarian Corsola: The main defensive core of the team; G-Corsola has incredible 400/400 Def/SpDef stats w/ Eviolite, making it a good SR setter and basically the only hazard setter on this team. Night Shade is G-Corsola's main source of damage (in case it gets Taunted), Will-O halves Attack (crippling Physical attackers), which is immensely useful, SR is self-explanatory, and Strength Sap keeping it healthy.