WooHoo New Drops!
Personally I think that it's kind of a shame that we only really got offensive juggernauts through the Tier shifts and lost a defensive staple, which is definitely an overall net loss for fat in general. But then again I am le big stall player so take that with a grain of salt, especially since I seriously doubt that fat teams that previously weren't using Slowking are gonna change significantly. As for the individual drops I think they're all (aside from the Owl) gonna summent themselves as either Tier staples or even be somewhat broken depending on how their sets develop, but personally I've not really been struggling with any of them as of late. Anyhow I'd like to give my thoughts about each individual mon and how I think they will (or won't) affect the metagame, starting with the weakest one.
Owl City
Starting off with the weakest mon is kind of a cop out, but I want an excuse to theorymon so hush. Decidueye has absolutely no business staying UU by usage at the end of the month unless someone figures out some kind of super cracked niche it randomly has access to before next May shifts. Generally I doubt that Offensive sets will be very worthwhile in the current metagame because of how stiff the Ghost-type competition is in UU, but Defensive sets definitely look atleast somewhat decent despite the numerous flaws they have attached to them.
Defensive Sets
Initially it's stats and movepool looks promising with access to a plethora of Utility options like Knock Off, U-Turn, Defog and Roost which allow it to play defense decently. This alongside the useful resistances to Ground, Electric, Water and the ever important Fighting Immunity would lead you to believe that it could somewhat consistently come in to get these tools off, right?
The main issue with this however is that it really just is not built for this role because of how it's Defensive Typing doesn't synergize with it's Defensive Stats whatsoever. It's built like a Specially Defensive mon but it's typing only really let's it check Shocks with such a spread, however as a Physically Defensive tank it has to rely on 78/75 bulk which is just awful. Personally I still think that these tools are the main thing Decidueye can do to differenciate itself from the superior options because of how it's the only mon with the Knock Off + Defog combination in the entire dex, but it's just so bleh.
Offensive Sets
Generally I don't think that Specially Offensive sets are going to see much usage because they're mostly outclassed by Gengar. This is mainly because Decidueye is both weaker and slower, while not really having a big leg up defensively either (the Fimp Resistance makes Gar much harder to revenge kill ironically enough). The tier is full of good Ghost resists which run a lot of special bulk specifically to deal with Gengar, which is why I don't think that sets focused on Special Offense are going to be very prevelant.
The afforementioned reasons are mainly why I think that Choice Band is the set with the most potential, mainly because of how it has a couple of tools which make it unique in comparison to the other attackers in the tier. Long Reach gives it the freest punish on Talonflame ever thanks to Knock Off and also makes clicking stuff like Leaf Blade, U-Turn and Shadow Sneak a lot easier. Access to a decent Physical Ghost Stab in Spirit Shackle fixes the main issue most Physical Ghosts have to deal it while also making it rougher to pivot around in comparison because of the trapping effect. I still don't think this set will be very good because of how mediocre it is defensively and how it has to choose between more than 4 options, but it looks somewhat ok atleast.
Anyway now that I'm done with the bad one it's time to tackle the drops people are actually excited for, those being Iron Leaves and Pelipper and Quaquaval. I predict that all of them are going to have a gigantic impact on the UU metagame because of the many unique tools they bring to the table.
5G Brainrot
Iron Leaves is an interesting mon that I really don't have a lot to say about because of how extremely obvious it's intended playstyle is. It has access to decent coverage alongside Swords Dance so it's obviously inclined to run that, which means that it'll most likely become a Hyper Offense staple overnight. Generally it has a lot going for it such as being one of the few
good Offensive Grass-Types we have access to in the tier, which alongside it's solid bulk allows it to use mons like Scarf Pawmot, Tera Blastless Sandy Shocks, Gastrodon and Tauros-Water as setup fodder. Being a setup sweeper that also shits on Quagsire is also a nice bonus, especially since unlike other alternatives like Gyarados and Hawlucha the opportunity cost isn't as severe. Grass + Psychic + something for Steels can be a pretty rough combination to switch into as seen with Gallade, which Iron Leaves also has access to thanks to Close Combat or even Tera Blast Fire. 104 base Speed is also just a good speed tier in general, but also comes with the bonus of putting you above the likes of every Scarfer slower than Pawmot after a Booster Energy.
Now this looks all fine and dandy on paper, but the real issue with the SD variant is mainly just how easy it is to revenge kill. 90/88 Physical Bulk is nothing to sneeze at as far as Offensive mons go, but the real kicker comes with the typing. It can not be understated just how awful Psychic/Grass is defensively in this tier because of how dominated it currently is by strong Bug, Flying, Dark and Ghost types. The lack of a resistance to common priority like Bullet Punch and Extreme Speed is further exhasperated by the weakness to First Impression and Sucker Punch and it's Speed Tier is just bellow mons which carry Super Effective STAB moves like Gengar, Iron Jugulis, Kilowattrel and Noivern.
However this is where Terastilization as a mechanic comes in and basically saves this mon from the majority of it's flaws. Not only can it potentially use this mechanic Offensively by using a Tera which makes either Stab stronger or use something like Tera Blast Fire in order to smack fat mons that can tank it's type combo, but it can also use Tera defensively in order to circumvent it's biggest issue; the awful typing. Personally I've been experimenting with Tera Fire as the defensive typing since gives you a resistance to Bug and Steel while also making you immune to Talonflames omnipresent burns. There are still a lot of issues with this set of course like how Choice Banded Lokix can still OHKO you with Tera Bug First Impression, but hey you win some you lose some amirite :>.
Outside of Swords Dance I really don't think anything else is worth theorymonning over at the moment, since Choice Band and Choice Scarf both look solid on papers, so they could realistically speaking see some usage. I could also talk about how it totally will revolutionize Electric Terrain as a playstyle and make it even remotely viable, but I'd rather leave the coping to the experts if you catch my drift. Overall there really isn't much else to say about Leaves, it's just extremely good at what it does while also being very Tera reliant.
"Skillless" does not even begin to describe this pokemon, I am beyond convinced at this point. After spending two months in OU they finally let this POS drop last minute because of some dumb weather wars they could've prevented by just banning the totally balanced Dinosaur. Anyhow because of OU's weather issues we now have to deal with this annoying playstyle, yaaaay. Outside of a rant I really don't have much to say about rain that hasn't already been said plenty of times already, especially since I both CT the shit out of it unintentionally and also never play it so it might aswell not exist.
Gay Duck
And finally we have Quaquaval which is definitely an interesting mon to theorycraft for solely because of how many tools it has at it's disposal. There's obviously an intended way to use it since it has access to some incredibly nutty tools in the form of Aqua Step + Swords Dance + Moxie, but it also has a lot of utility options alongside that. Options like Rapid Spin and Roost managed to make it's middle stage evolution viable in PU after all, so it wouldn't be surprising if we see something like that in UU aswell. Anyhow onto the actual theorycrafting, starting with offensive variants.
Generally I think that the main version of Quaquaval we're gonna be seeing for the rest of April is going to be some form of offensively spec'd Duck, mainly the Swords Dance variants. With access to a strong Water Stab that also boosts your Speed alongside a Life Orb Close Combat that can 2hko Quagsire, it very much seems like a strong choice in the current metagame, especially for Hyper Offense teams. Of course Swords Dance + 3 attacks isn't the only set it can run, since the speed boost you gain from Aqua Step can offset the mediocre speed you'd have by running a Bulky setup variant. You retain the ability to more consistently use Quagsire as setup fodder with Taunt + Roost and some Bulk, which also gives you more longevity. Pair this with either Bulk Up or Swords Dance and you've got yourself a solid, albeit one dimensional set. These are obviously two extremes as you could easily run something like Roost + SD + 2a or Taunt + SD + 2a or even Sub + SD + 2a, but theorycrafting every possible SD set would get kinda repetitive.
I also think that Choiced sets could potentially be decent. Choice Band is obviously the main set here and it's purpose is fairly obvious, it just hits really hard and ticks both the Priority and Pivot boxes thanks to Aqua Jet and U-Turn. Moxie + Aqua Step also makes it into a potentially formidable lategame cleaner even though it is initially a bit prediction reliant and also has to choose between a couple of moveslots. Scarf meanwhile sounds solid on paper because of how Moxie Scarfers typically end up being great cleaners, which alongside U-Turn and the spammable Close Combat makes it pretty formidable.
However I would also like to make a case for variants which use Rapid Spin, mainly the Offensively oriented ones akin to Tatsugiri. A general complaint I see regarding the formes of hazard removal in UU is that the mons which have access to them suck individually, which is understandable given that none of our Spinners would currently be UU by usage if not for Rapid Spin being in their arsenal. Quaquaval is interesting in this regard because it's just genuinely good as an individual pokemon, which might lead to Offensive Rapid Spin sets taking off and becoming standard. Granted this is just me theorymonning since I have never seen anyone actually use this yet, but it sounds interesting, especially since Quaquaval is the only Spinner with access to reliable recovery.
Alright so those are most of my thoughts regarding the drops we're gonna have to deal with throughout April. We definitely had a large metagame shakeup which I think is a good thing because to me UU has been feeling pretty stale as of late and desperately needed something to change. I could see Quaquaval and Iron Leaves being potentially broken in the future, but they've only been live for two days now and I haven't really played with or against them enough to form an opinion. Rain meanwhile is the worst and I want it gone >:(.
aka QUAVO. In isolation, it's already really constraining and unfun to play against. I've certainly encountered many variations of Quavo whether it's taunt, BU Roost, SD, or even scarf from experimenting on the ladder. 
has been mentioned as a common check and even that can't fit onto every team structure, not to mention Quavo could use tera grass/electric to overpower it, this is basically UU's version of Seismitoad being on every OU team just to not lose to Dracovish kinda moment but not as bad. 
feels like a band-aid solution since it doesn't resist cc and really should be paired with another intimidator such as 
, it honestly feels like you have to actively cheat ur defensive coverage just to not get rolled over by the duck and rain which I have def seen ppl run it on.
, 
and 
who resists both of Quavo's stabs although it does need to respect Ice Spinner with that said. 
and 
are also somewhat soft checks to Quavo just to prevent speed boosting if they are running Water Absorb and Storm Drain respectively. However, that has its own issues as Quavo would end up overpowering it with CC and maybe Taunt. Honestly if I saw 
, Floatzel 
, and Kilowattrel 
, with three filler slots that usually consist of some combo of a Steel (see: 
), a Grass-type hazard remover (see: 
), and one or more extra Rain abusers, usually something like Drednaw 
, Golduck 
, or Barraskewda 
.
