Managed to hit the top 5 with this team, so I thought I'd share it.





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It's a balance team with a pretty straightforward recipe. Two bulky pivots, two nukes, and two offensive* utility pokemon that can also pivot but more rarely. For both the bulky pivots and the nukes, one is physical and one is special. The goal is to dance around with the pivots until an opportunity arrises to unleash a nuke. Greninja lays spikes to take advantage of all the switching this team forces, and also provides revenge killing and priority. *Mew is offensive when it transforms into an opposing hard-hitter, but its primary effect is to force switches through Imprison Transform, while also offering a tool for weakening stall.
Also it CAN be an obnoxious win-con if it's still alive when the opponent is down to their last mon, but for this you more or less need to play a 5 vs 6 game so it doesn't happen often.
Most of the mons are pretty self-explanatory. The main innovation I suppose is RoostVest Decidueye. I really wanted to explore the new Regenerator-style mons provided by this format, and was hoping to find one that provided pivoting, Knock Off, and no weakness to Stealth Rock so that it can actually use Assault Vest comfortably, similar to Flipped Mienshao and Cyclizar. To my surprise, Decidueye ended up being the one to fit the bill. While its typing does have a lot of weaknesses, it pairs really well with Light Screen from Corviknight, which allows it to tank an amazing number of super effective hits, which it then heals off next time it comes in. Remember that its job is to absorb special hits and either Knock or U-turn the switchin. Decidueye usually can't stay in long as it doesn't have much attacking power, can't handle physical switch-ins, and needs to switch to stay healthy, so it's very rare for Spirit Shackle's trapping effect to actually get utilized, but on the few occasions it does, it's pretty sweet. I also tried the Hisui version but found it much worse because it just got destroyed by Hurricanes, and I like the immunity to Choiced Fighting moves and Rapid Spin. A couple (albeit rare) pokemon that Decidueye's typing does completely block are Sandy Shocks, Rotom-W, and Regieleki (very nice when the opponent uses the latter as their spinner). I do sometimes use Tera on Decidueye if the opponent has a lot of special attackers. Tera Water greatly expands its staying power, though I only do this if I have to.
The team struggles against certain attackers like Urshifu-R and DD Baxcalibur (as well as para spam but that'll be gone soon), against which my main defense is to Tera Water on Great Tusk to absorb the hit and KO back, along with wearing them down with Rocky Helmet and Spikes, and Transform Mew if I can get it in safely. The other two mons I Tera are Ground Volcarona if I see a window to sweep with it, and Water Greninja in case I really need more power behind its priority. I have never Tera'd Corv or Mew (as you can see by their lack of Tera assignments).
A quick aside. I don't see too many pokemon using Roost as a Trademark here, maybe because most are weak to SR and can't use AV, but I do see a decent number of Roost Corviknight, which seems like a good idea thanks to its SR neutrality, pivoting, and great typing. But I think this is a terrible option for Corv, because it completely invalidates its ability to switch into Ground attacks. All Flying types have this problem (this is another perk for Decidueye) but it is particularly bad for Corviknight. Whenever I see a Corv with a Roost TM, I prepare myself to go to town with Headlong Rush on Tusk.
Here are some replays that do a good job at showcasing Decidueye: