This core utilizes the Parting Shot/U-turn core of Alolan Persian and Swellow to gain momentum versus their respective checks and counters, as each other take advantage of the Pokémon they lure in respectively. Persian lures in Fighting and Dark Types, as well as dedicated physically defensive Pokémon that Swellow loves to nuke, such as Scrafty, Pangoro, and Donphan, while Swellow lures in stuff like Bronzong and Cresselia, stuff that Persian loves to mess around with.
Persian acts as a pivot to Swellow, it checks a good portion of the metagame thanks to it´s ability Fur Coat, and it also acts as a stallbreaker to make it even more easier for Swellow to break down the opposing team, thanks to Taunt and Toxic respectively, and it also has acces to Foul Play to stop setup sweepers such as Feraligatr and Doublade. Parting Shot is a really cool move as it does essentially the same thing as Volt Switch and U-turn, but instead of dealing damage it reduces the Atk and SpA of the opposing Pokémon by 1 stage, making it easier for the Pokémon that will come in place of Persian. And to make it even better, Persian also comes with an ace in the hole, which is Z-Parting Shot. This Z Move will make Persian use Parting Shot, but this time it´s replacement will recover it´s entire health, giving a potentially weakened Pokémon a 2nd chance in the match. The EVs spread allows Persian to outspeed Lycanrock Midday Form, the rest was put in Def to increase it´s bulk.
I´m pretty sure I don´t need to explain what Choice Specs Swellow does. It´s one of the best wallbreakers in the tier, and for a good reason. With a base speed of 125, Swellow outspeeds the vast majority of the unboosted metagame, which makes it a very scary late game cleaner once it´s checks and counters have been weakened/removed. Boomburst will be your main STAB and the move you will go for most of the time, being a 140 base power move with no drawbacks that very few Pokémon can switch into, and thanks to Swellow´s ability Scrappy, Boomburst also ignores the inmunity that Ghost Types have against Normal Type moves, which coupled with it´s acces to Heat Wave, leaves Rock Types as the only solid answer to Swellow. U-turn as the 3rd move to take advantage of the switches that Swellow forces as well as gain momentum. The last move slot can be toyed around with.
I decided to pair them with Feraligatr, as Persian doesn´t have the offensive pressence to heavily weaken Swellow´s switch-ins. Feraligatr is another very potent threath in the RU metagame thanks to it´s ability Sheer Force, which boosts the strength of it´s attacks that have secondary effects by 30%, and nullifies Life Orb recoil on top of that, giving Feraligatr a tremendous wallbreaking/late game sweeper potential. Feraligatr also goes really well with Persian and Swellow, as it can help them deal with most stuff that each other lure in, and overload some checks and counters they share. And last but not least, it takes full advantage of Persian´s Parting Shot and Z-Parting Shot, as it gives Feraligatr much more freedom and opportunities to set up. Feraligatr´s set and coverage can change depending on what the rest of the team needs. On the Dragon Dance set however, Jolly is the preffered nature, as it allows Feraligatr to outspeed the entire unboosted metagame (barring Accelgor), and even some Choice Scarf Pokémon, after a Dragon Dance.