UU Victim of the Week! (Week Twenty-Seven: Contrary Serperior)

[dingbat]

Reserving dugtrio as check lmfao

I am one lazy ass madafaka .-.

Dugtrio @ Choice Band
Ability: Arena Trap
4 HP, 252 Atk, 252 Spe
Jolly Nature

Basically, throw (healthy) Dugtrio against Nidoking on a free switch-in and watch it die, nice 'n quickly. LO Sucker Punch from King doesn't even OHKO it too, will show calcs later

 

[glock in my toyota]

I'd like to nominate SpDef Seismitoad as a check.

Seismitoad @ Leftovers
Ability: Water Absorb
EVs: 232 HP / 24 Atk / 252 SpD
Careful Nature
- Earthquake
- Scald
- Stealth Rock
- Toxic / Knock Off

Now I know what you must be thinking... "uh dood wtf that isnt viable at all stop pls" but hear me out. Toad resists Nidoking's most powerful move, Sludge Wave, and takes Earth Power quite well (252 SpA Life Orb Sheer Force Nidoking Earth Power vs. 232 HP / 252+ SpD Seismitoad: 161-191 (39.3 - 46.6%) -- guaranteed 3HKO) as well as taking his other viable options (Ice Beam, Superpower, TBolt). Toad's ability to come in on any move from King and be guaranteed to live 2 hits is impressive, and Toad can proceed to likely OHKO King in retaliation (24 Atk Seismitoad Earthquake vs. 4 HP / 0 Def Nidoking: 264-312 (86.8 - 102.6%) -- 50% chance to OHKO after Stealth Rock).

Now for the whole "Be viable outside of just being a certain couner to one mon" part. I would just like to point out how good Toad is for countering Mega Blastoise. It takes its Special Hits with ease, and is immune to it's STAB moves, actually gaining HP from them. Seismitoad works much like a specially defensive Swampert, setting up Stealth Rock, having the ability to Burn things w/ Scald, having a semi-offensive STAB Earthquake, but Toad also has the ability to Knock Off some important items (Specs, Scarf, Life Orb etc.) to reduce the amount it takes from stronger hits. OR it can spread Toxic onto things like Swampert, or other bulky mons.

TL;DR: Use Toad, its a Specially Defensive Swampert.

 

[President Shinra]

Snorlax @ Assault Vest
Ability: Thick Fat
EVs: 252 Atk / 252 Def / 4 SpD
Adamant Nature
- Return
- Pursuit
- Earthquake
- Crunch

252 SpA Life Orb Sheer Force Nidoking Earth Power vs. 0 HP / 4 SpD Assault Vest Snorlax: 114-136 (24.7 - 29.5%) -- 100% chance to 4HKO
252 SpA Life Orb Sheer Force Nidoking Sludge Wave vs. 0 HP / 4 SpD Assault Vest Snorlax: 121-144 (26.2 - 31.2%) -- guaranteed 4HKO
252 SpA Life Orb Sheer Force Nidoking Ice Beam vs. 0 HP / 4 SpD Assault Vest Thick Fat Snorlax: 39-47 (8.4 - 10.1%) -- possibly the worst move ever
4 Atk Life Orb Nidoking Superpower vs. 0 HP / 252 Def Snorlax: 237-281 (51.4 - 60.9%) -- guaranteed 2HKO

252+ Atk Snorlax Earthquake vs. 4 HP / 0 Def Nidoking: 264-312 (86.8 - 102.6%) -- 18.8% chance to OHKO
252+ Atk Snorlax Earthquake vs. -1 4 HP / 0 Def Nidoking: 398-470 (130.9 - 154.6%) -- guaranteed OHKO
252+ Atk Snorlax Return vs. -1 4 HP / 0 Def Nidoking: 306-360 (100.6 - 118.4%) -- guaranteed OHKO

Snorlax can take 2 Superpowers barring crazy max damage (considering the -1 attack), and can take a STAB special move + Superpower after rocks (again barring max damage), and after -1 can KO with Return or EQ. If Superpower is not used, Snorlax 2HKOes, but Nidoking cannot 3HKO and will still lose.

 

[imaloony]

My personal brew; I've used it to great effect. I'll call it a check just because with rocks up it has a small chance to 2HKO with a predicted Sludge Wave followed by a second Sludge Wave.

Machamp@Assault Vest
252HP/232Att/24SpDef
Adamant Nature
Ability: Guts
- Close Combat
- Earthquake
- Knock Off
- Bullet Punch

Before you say anything, if you want to scoff this set because it isn't D-Punch No Guard, I'll point out that D-Punch No Guard AV Machamp also works, I just like this one better personally, but you still have to carry EQ over Stone Edge in that case.

On the Defensive:

252+ SpA Life Orb Sheer Force Nidoking Earth Power vs. 252 HP / 24 SpD Assault Vest Machamp: 153-181 (39.8 - 47.1%) -- guaranteed 3HKO
252+ SpA Life Orb Sheer Force Nidoking Sludge Wave vs. 252 HP / 24 SpD Assault Vest Machamp: 161-191 (41.9 - 49.7%) -- guaranteed 3HKO
4 Atk Life Orb Nidoking Superpower vs. 252 HP / 0 Def Machamp: 138-162 (35.9 - 42.1%) -- guaranteed 3HKO
4 Atk Life Orb Nidoking Sucker Punch vs. 252 HP / 0 Def Machamp: 45-55 (11.7 - 14.3%) -- possible 7HKO

On the Offensive:

232+ Atk Machamp Earthquake vs. 0 HP / 0 Def Nidoking: 294-346 (97 - 114.1%) -- 81.3% chance to OHKO
232+ Atk Machamp Bullet Punch vs. 0 HP / 0 Def Nidoking: 59-70 (19.4 - 23.1%) -- possible 5HKO

Eat the damage on the switch, hit it with an EQ, and if it survives, you finish it with a Bullet Punch. Quick and clean.
(And if anyone wants to know why I like this Guts Variant, it's because I like to be able to eat scalds and hit back with a surprise CC.)

 

[Mahmudkipz]

I'd like to nominate SpDef Seismitoad as a check.

Seismitoad @ Leftovers
Ability: Water Absorb
EVs: 232 HP / 24 Atk / 252 SpD
Careful Nature
- Earthquake
- Scald
- Stealth Rock
- Toxic / Knock Off

Now I know what you must be thinking... "uh dood wtf that isnt viable at all stop pls" but hear me out. Toad resists Nidoking's most powerful move, Sludge Wave, and takes Earth Power quite well (252 SpA Life Orb Sheer Force Nidoking Earth Power vs. 232 HP / 252+ SpD Seismitoad: 161-191 (39.3 - 46.6%) -- guaranteed 3HKO) as well as taking his other viable options (Ice Beam, Superpower, TBolt). Toad's ability to come in on any move from King and be guaranteed to live 2 hits is impressive, and Toad can proceed to likely OHKO King in retaliation (24 Atk Seismitoad Earthquake vs. 4 HP / 0 Def Nidoking: 264-312 (86.8 - 102.6%) -- 50% chance to OHKO after Stealth Rock).

Now for the whole "Be viable outside of just being a certain couner to one mon" part. I would just like to point out how good Toad is for countering Mega Blastoise. It takes its Special Hits with ease, and is immune to it's STAB moves, actually gaining HP from them. Seismitoad works much like a specially defensive Swampert, setting up Stealth Rock, having the ability to Burn things w/ Scald, having a semi-offensive STAB Earthquake, but Toad also has the ability to Knock Off some important items (Specs, Scarf, Life Orb etc.) to reduce the amount it takes from stronger hits. OR it can spread Toxic onto things like Swampert, or other bulky mons.

TL;DR: Use Toad, its a Specially Defensive Swampert.

SpDef Toad is also a really nice answer to non-HP Grass Ampharous which is really cool ;o

 

[CoolStoryBrobat]

Top 3 Checks/Counters to Mixed Nidoking have been chosen (In no specific order):

Top 3 Counters:

Vaporeon - Sleepless
Porygon2 - Colbrushie
Cresselia - Billtodamax

Top 3 Checks:

Snorlax - President Shinra
Machamp - imaloony
Seismitoad - ~Volbeatdown~

Congratulations President Shinra, you've earned 1 Leaderboard Point for winning 3 times. OP will be updated accordingly. Next week's Victim is something that's gonna require a bit of innovation to take on once it gets going...At least, I hope:

Cloyster @ Life Orb / White Herb
Ability: Skill Link
EVs: 252 Atk / 4 SpA / 252 Spe
Naughty / Adamant Nature
- Hydro Pump / Explosion / Ice Shard
- Icicle Spear
- Rock Blast
- Shell Smash

 

[slated]

reserving quaggy

 

[Water Drone]

reserving magneton as a solid check

 

[dodmen]

Nasty Plot Lucario as a check.

Lucario @ Life Orb
Ability: Inner Focus
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
- Nasty Plot
- Aura Sphere
- Flash Cannon
- Vacuum Wave

The very very worst that could happen after you come in on a free switch:
+2 252+ Atk Life Orb Cloyster Ice Shard vs. 0 HP / 0 Def Lucario: 100-118 (35.5 - 41.9%) -- guaranteed 3HKO

The very very least that you could possibly do to it (assuming White Herb has activated):
252+ SpA Life Orb Lucario Vacuum Wave vs. 0 HP / 0 SpD Cloyster: 322-382 (133.6 - 158.5%) -- guaranteed OHKO

You can't even get flinched by King's Rock Ice Shard n_n so yeah Vacuum Wave Lucario 100% checks Cloyster no matter what and that's all there is to it.

 

[Kink]

Check

Aggron-Mega @ Aggronite
Ability: Filter
EVs: 252 HP / 4 Atk / 252 SpD
Careful Nature
- Head Smash/Low Kick
- Rest
- Sleep Talk
- Roar

Plain and simple, observe the calcs below. I will provide a short blurb after.

If Cloyster Switches In:
0 Atk Mega Aggron Head Smash vs. 0 HP / 0 Def Cloyster: 172-204 (71.3 - 84.6%) -- 68.8% chance to OHKO after Stealth Rock
0 Atk Mega Aggron Low Kick (100 BP) vs. 0 HP / 0 Def Cloyster: 116-138 (48.1 - 57.2%) -- guaranteed 2HKO after Stealth Rock

If 1vs1 w/out smashing:4 SpA Life Orb Cloyster Hydro Pump vs. 252 HP / 252 SpD Mega Aggron: 122-146 (35.4 - 42.4%) -- guaranteed 3HKO
0 Atk Mega Aggron Low Kick (100 BP) vs. 0 HP / 0 Def Cloyster: 116-138 (48.1 - 57.2%) -- guaranteed 2HKO after Stealth Rock

If 1vs1 w/ smashing:
+2 4 SpA Life Orb Cloyster Hydro Pump vs. 252 HP / 252 SpD Mega Aggron: 246-290 (71.5 - 84.3%) -- guaranteed 2HKO
0 Atk Mega Aggron Head Smash vs. -2 0 HP / 0 Def Cloyster: 344-406 (142.7 - 168.4%) -- guaranteed OHKO
0 Atk Mega Aggron Low Kick (100 BP) vs. -2 0 HP / 0 Def Cloyster: 230-272 (95.4 - 112.8%) -- guaranteed OHKO after Stealth Rock


The one thing M-Aggron cannot do is switch in on a neutral Hydro Pump as Aggron, however, cloyster will seldom choose that option, as most people will not assume M-Aggron to be a 1vs1 counter. It's pre-mega status is the only thing that keeps this guy a check.

Another note of interest is that one can simply go sturdy with Aggron and headsmash prior to mega-evolving if in a 1vs1 situation. However, the reliability of the M-Aggron set makes that a less favourable, if not a still effective option.

 

[Thisbemyalt]

Porygon2 @ Eviolite
Ability: Download/Analytic
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
- Thunderbolt/Ice beam
- Tri Attack
- Toxic
- Recover
I'm using Porygon-2 as a check. Porygon-2 can reliably come in on any move that cloyster can dish out. Pory comes in on a setup move and either kills or forces closyter out. If cloyster setup the turn you brought in pory then you can just ohko is but if closter tried to do damage well then congratulations on a yummy snack cause you are gonna be able to get off a clean recover back to full if cloyster sets up on your recover well then it is about to die next turn cause you are living any hit. Now I suppose I should address one way cloyster can kill pory with the set you have provided, that would be the rarest and hugest set of which I have never seen, LO explosion. LO is almost never run on a cloyster but at least I have seen it before while explosion is just no where that I have seen. If cloyster is plus two it has a small chance to kill pory with LO explosion. This however really does not matter as I stated these two by themselves are rare but together are just too huge for anyone on UU ladder and even if it does kill you the monster that is cloyster after setup is dead. Also as Im sure you all know pory is a great wall overall and can dish out some powerful moves so he is very viable outside of cloyster.

calcs from cloyster

252+ Atk Life Orb Cloyster Icicle Spear (5 hits) vs. 252 HP / 252+ Def Eviolite Porygon2: 125-155 (33.4 - 41.4%) -- guaranteed 3HKO
252+ Atk Life Orb Cloyster Explosion vs. 252 HP / 252+ Def Eviolite Porygon2: 161-191 (43 - 51%) -- 5.1% chance to 2HKO
+2 252+ Atk Life Orb Cloyster Icicle Spear (5 hits) vs. 252 HP / 252+ Def Eviolite Porygon2: 255-300 (68.1 - 80.2%) -- guaranteed 2HKO
+2 252+ Atk Life Orb Cloyster Explosion vs. 252 HP / 252+ Def Eviolite Porygon2: 322-380 (86 - 101.6%) -- 12.5% chance to OHKO

calcs against cloyster

+1 0 SpA Porygon2 Thunderbolt vs. 0 HP / 0- SpD Cloyster: 420-496 (174.2 - 205.8%) -- guaranteed OHKO
+1 0 SpA Porygon2 Tri Attack vs. 0 HP / 0- SpD Cloyster: 280-331 (116.1 - 137.3%) -- guaranteed OHKO
Or if you are analytic:
0 SpA Analytic Porygon2 Tri Attack vs. 0 HP / 0- SpD Cloyster: 244-288 (101.2 - 119.5%) -- guaranteed OHKO

 

[President Shinra]

EBelt Jirachi as an offensive check:

Jirachi @ Expert Belt
Ability: Serene Grace
EVs: 252 Atk / 4 SpA / 252 Spe
Naive Nature
- Iron Head
- Fire Punch
- Energy Ball
- Stealth Rock

This set can take (most) of Cloyster's hits and crush it in return with Energy Ball. I say (most) because this does not include LO Explosion, which usually OHKOes at +2. Barring this, most moves will fail to kill Rachi, even at +2.

+2 252+ Atk Life Orb Cloyster Icicle Spear (5 hits) vs. 0 HP / 0 Def Jirachi: 235-280 (68.9 - 82.1%) -- guaranteed 2HKO after Leftovers recovery
+2 252+ Atk Life Orb Cloyster Rock Blast (5 hits) vs. 0 HP / 0 Def Jirachi: 155-190 (45.4 - 55.7%) -- approx. 4.3% chance to 2HKO after Leftovers recovery
+2 4 SpA Life Orb Cloyster Hydro Pump vs. 0 HP / 0- SpD Jirachi: 300-355 (87.9 - 104.1%) -- 25% chance to OHKO (Both pretty shaky and pretty uncommon)
+2 252+ Atk Life Orb Cloyster Explosion vs. 0 HP / 0 Def Jirachi: 312-368 (91.4 - 107.9%) -- 50% chance to OHKO

In return:
4 SpA Jirachi Energy Ball vs. 0 HP / 0- SpD Cloyster: 272-320 (112.8 - 132.7%) -- guaranteed OHKO

 

[glock in my toyota]

god damn i wanted empoleon

For this poor victim, I will be using Registeel as a counter.

Registeel @ Leftovers
Ability: Clear Body
EVs: 252 HP / 4 Def / 252 SpD
Careful Nature
- Iron Head
- Thunder Wave
- Stealth Rock
- Protect / Block

The functionality of this counter is simple: Switch in, Eat up hits (yes even hydro pump), Thunder Wave it, Paraflinch it. Registeel Oh my lord, you take NOTHING from Cloyster. Registeel is an extremely safe switch-in to Cloyster, as it resists both it's STAB moves and explosion, taking nearly NO damage from any move from Cloyster. Registeel then proceeds to Thunder Wave the Cloyster, severely crippling it, and it can paraflinch the Shell of Doom with Iron Head. Stealth Rock is standard on Registeel, so you can make yourself even more useful by setting up hazards. Protect is here for scouting out moves from other Pokemon, namely Infernape, to see if it is Physical or Special. Hell, if you really hate Cloyster, you can run block, so that it cannot switch out as it gets paraflinched to death. Registeel acts as a nifty counter to (Non-SubToxic) Jirachi. It can T-Wave the Rachi, making it not nearly as useful.

+2 252+ Atk Cloyster Icicle Spear (5 hits) vs. 252 HP / 4 Def Registeel: 125-150 (34.3 - 41.2%) -- approx. 77.4% chance to 3HKO after Leftovers recovery
+2 252+ Atk Cloyster Rock Blast (5 hits) vs. 252 HP / 4 Def Registeel: 85-100 (23.3 - 27.4%) -- possible 5HKO after Leftovers recovery
+2 4 SpA Cloyster Hydro Pump vs. 252 HP / 252+ SpD Registeel: 111-132 (30.4 - 36.2%) -- guaranteed 4HKO after Leftovers recovery
0 Atk Registeel Iron Head vs. 0 HP / 4 Def Cloyster: 42-49 (17.4 - 20.3%) -- possible 5HKO --(Paralysis is enough if you are really unlucky with Flinch)--

TL;DR -- Registeel beats Cloyster, as it eats up it's hits and cripples it right back.

 

[dingbat]

reserving Blastoise-Mega as a check

Blastoise @ Blastoisinite
Ability: Rain Dish --> Mega Launcher
EVs: 132 HP, 252 SpA, 124 Spe (this spread was originally made in order to outspeed Victini creepers, but w/e)
Modest Nature
-Hydro Pump
-Dragon Pulse
-Aura Sphere/Dark Pulse
-Rapid Spin

Mega Blastoise in general is an excellent spinner/bulky attacker that fits on a plethora of teams as it is able to threaten a vast portion of this tier from just three of its attack moves.
Sucks that Mega Blastoise can't handle a WTFBOOM from Cloyster, but otherwise it is a solid check that can come in on the Shell Smash, tank a +2 move from Cloyster, and proceed to KO it back with absolutely no effort.

+2 252+ Atk Life Orb Cloyster Rock Blast (5 hits) vs. 132 HP / 0 Def Mega Blastoise: 275-325 (82.8 - 97.8%)
+2 252+ Atk Life Orb Cloyster Explosion vs. 132 HP / 0 Def Mega Blastoise: 534-629 (160.8 - 189.4%) That's the WTFBOOM I'm talking 'bout

252+ SpA Mega Blastoise Hydro Pump vs. -1 0 HP / 0- SpD Cloyster: 318-375 (131.9 - 155.6%) heck, even Scald almost guarantees the OHKO

 

[Sage]

Sniping Empoleon since it's been up for way more than 6 hours sorry BoltsandBombers. Anyway, Empoleon As a Counter to each and every Cloyster.

Empoleon @ Leftovers
Ability: Torrent
EVs: 252 HP / 248 Def / 8 SpD
Calm Nature
- Flash Cannon
- Scald
- Defog
- Stealth Rock / Roar

He resists every move our shell smasher carries and tanks them. Using a Mixed Wall spread with 248 Def EVs and 8 SpD Calm because it's good for general defogging and the likes. On my phone, can't copy paste calcs, all are with +2 Adamant Life Orb to show Empoleon takes the strongest hits.

Explosion: 72 to 84.9
Icicle Spear: 25.5 to 30.9
Rock Blast: 37.2 to 43
Eats up Hydro and Ice Shard with around 35% for +2 LO former, Ice Shard does like 15

Flash Cannon OHKOes minus 1 SpD, and White Herb can't 2HKO you without Explosion which you can't use twice lol. GG Cloyster. I'll edit calcs later sorry Brobat.

EDIT: Gave back to BoltsandBombers, he was unaware of time limit.

 

[boltsandbombers]

Sage of the 6 Meh, oh well. I knew that there was a time limit for how long you could reserve something without posting it, but I didn't know it was 6 hours.

 

[Sage]

Yeah sorry bud, if you really want it take it since you didn't know.

 

[glock in my toyota]

King UU, I would like to point out that in your calc, M-Aggron's attacks on Cloy is against a -2 Defense Cloyster. Shell Smash leaves you at -1 Defense, not 2. Please Fix.

 

[Sage]

Cobalion as Check

Cobalion @ Leftovers
Ability: Justified
EVs: 252 HP / 32 Atk/ 224 Spe
Jolly Nature
- Stealth Rock
- Volt Switch
- Close Combat
- Thunder Wave

 

[boltsandbombers]

Empoleon as a Counter

Happy Feet (Empoleon) @ Leftovers
Ability: Torrent
EVs: 248 HP / 252 Def / 8 SpD
Calm Nature
- Scald
- Roar
- Defog
- Stealth Rock

Empoleon is a great counter to all Cloyster variants due to its respectable bulk and water steel typing. No matter what Cloyster goes for, Empoleon is always a safe switch in. If it tries to boost up, Empoleon can phase it out with roar or fish for a burn with scald taking advantage of its pitiful special defense. It can easily eat up icicle spear and rock blast, quad resisting its main stab as well, which make up Cloysters main offensive moves (even with a life orb and +attack nature). However, while a mixed defensive spread isnt always the best on pokemon such as empoleon, it is necessary to survive the OHKO from +2 Adamant Life Orb Explosion after stealth rock damage.

Calcs:
+2 252+ Atk Life Orb Cloyster Icicle Spear (5 hits) vs. 248 HP / 252 Def Empoleon: 95-115 (25.6 - 30.9%) -- approx. 94.9% chance to 4HKO after Stealth Rock and Leftovers recovery
+2 252+ Atk Life Orb Cloyster Rock Blast (5 hits) vs. 248 HP / 252 Def Empoleon: 135-160 (36.3 - 43.1%) -- guaranteed 3HKO after Stealth Rock and Leftovers recovery
+2 252+ Atk Life Orb Cloyster Explosion vs. 248 HP / 252 Def Empoleon: 268-316 (72.2 - 85.1%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery

0 SpA Empoleon Scald vs. -2 0 HP / 0- SpD Cloyster: 198-233 (82.1 - 96.6%) -- guaranteed 2HKO (basically kills after one round of life orb recoil or after rocks, and the burn chance is always nice)

Here is why max defense is needed to fully counter cloyster:

+2 252+ Atk Life Orb Cloyster Explosion vs. 248 HP / 0 Def Empoleon: 347-409 (93.5 - 110.2%) -- 93.8% chance to OHKO after Stealth Rock

 

[Venduria]

Special Sweeper Toxicroak as a CHECK

Toxicroak @ Life Orb
Ability: Dry Skin
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Vacuum Wave
- Nasty Plot
- Sludge Wave
- Dark Pulse

252 SpA Life Orb Toxicroak Vacuum Wave vs. 0 HP / 0 SpD Cloyster: 242-289 (100.4 - 119.9%) -- guaranteed OHKO
That is best case scenario for Cloyster, running Adamant and White Herb.

If Cloyster is set up and is running Ice Shard, Toxicroak is 2HKOd.
+2 252+ Atk Cloyster Ice Shard vs. 0 HP / 4 Def Toxicroak: 163-193 (53 - 62.8%) -- guaranteed 2HKO

Can switch in on every move except Explosion, and survives unboosted Icicle Spear.
252+ Atk Cloyster Icicle Spear (5 hits) vs. 0 HP / 4 Def Toxicroak: 255-305 (83 - 99.3%) -- guaranteed 2HKO

Very similar to Lucario, except for the immunity to Hydro Pump. Toxicroak is pretty underrated as a threat, and can check/counter a good number of the bulky waters not named Swampert.

 

[The TurtleLord]

Jellicent (M) @ Leftovers
Ability: Water Absorb
EVs: 248 HP / 252 Def / 8 SpD
Bold Nature
- Scald
- Energy Ball
- Will-O-Wisp
- Recover

Jellicent is immune to hydro pump and explosion and takes small damage from icicle spear (26 - 32.2%). Jellicent can switch in on cloyster as it uses shell smash and then survive rock blast (+2 252+ Atk Life Orb Cloyster Rock Blast (5 hits) vs. 248 HP / 252+ Def Jellicent: 285-340 (70.7 - 84.3%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery) and then ohko with energy ball (0 SpA Jellicent Energy Ball vs. -1 0 HP / 0- SpD Cloyster: 354-418 (146.8 - 173.4%) -- guaranteed OHKO).

 

[imaloony]

I said Doublade, but after realizing my initial calculations were wrong, I have concluded that Doublade gets stomped all over by a Cloyster with Hydro Pump. As such, I present for your consideration (As a Check): Assault Vest Metagross (Defense creeped specifically for Cloyster)

Metagross@Assault Vest
252 HP/208 Att/48SpDef
Adamant Nature
Ability: Clear Body
- Hammer Arm
- Bullet Punch
- Earthquake
- Zen Headbutt/Meteor Mash/Rock Slide

When Cloyster comes in, it's your cue to switch out into the 'Gross on the predicted Shell Smash. At that point, you're one Hammer Arm and a Bullet Punch away from a dead Cloyster. Here are some fun time calcs.

On the Attack:

208+ Atk Metagross Hammer Arm vs. 0 HP / 0 Def Cloyster: 144-170 (59.7 - 70.5%) -- guaranteed 2HKO

On the Defense:

+2 4 SpA Cloyster Hydro Pump vs. 252 HP / 48 SpD Assault Vest Metagross: 144-169 (39.5 - 46.4%) -- guaranteed 3HKO after Stealth Rock
+2 252+ Atk Cloyster Icicle Spear (5 hits) vs. 252 HP / 0 Def Metagross: 145-170 (39.8 - 46.7%) -- guaranteed 3HKO after Stealth Rock
(Predict the switch and try to Hydro Pump/Icicle Spear the world without Smashing? Please, Metagross don't have time for that!)
4 SpA Cloyster Hydro Pump vs. 252 HP / 48 SpD Assault Vest Metagross: 72-85 (19.7 - 23.3%) -- guaranteed 5HKO after Stealth Rock
252+ Atk Cloyster Icicle Spear (5 hits) vs. 252 HP / 0 Def Metagross: 75-90 (20.6 - 24.7%) -- approx. 0.2% chance to 4HKO after Stealth Rock
(Get fed up at how amazing this blue monster in front of you is and try to blow up on it? Bomb Bunker Metagross doesn't even care!)
+2 252+ Atk Cloyster Explosion vs. 252 HP / 0 Def Metagross: 191-225 (52.4 - 61.8%) -- guaranteed 2HKO after Stealth Rock
(In all seriousness, the above WILL KO after a Hydro Pump, but you've successfully taken out Cloyster at that point, so I call it a win.)

 

[QuietHeatran]

Nominating standard defensive Swampert as check.

Swampert @ Leftovers
Ability: Damp
EVs: 252 HP / 252 Def / 4 SpD
Relaxed Nature
- Stealth Rock
- Scald
- Earthquake
- Roar

Either Swampert and Cloyster meet in lead matchup or Cloyster switches in on a mon that it can take a hit from.

If lead matchup, Swampert can set up rocks, scald or earthquake to break Cloyster's sash on the predicted shell smash. The next turn you can roar out Cloyster. Swampert is really good at taking hits and roaring out Cloyster. It's only a check because 1) Swampert can be worn down over a battle and 2) Swampert really can't ko Cloyster.

Regardless, Swampert is an amazing check if only for the fact that nearly every UU team can benefit from defensive swampert (maybe not as much as in the era of Victini, but it's still hella viable). Swampert is one of the only checks I run to Cloyster myself and I have yet to lose to a Cloyster sweep which I think is indicative of how useful Swampert is as a check especially given Wish support.

Since Cloyster can't explode because of the amazing situational ability Damp, here's some relevant calcs of what Cloyster CAN do to Swampert (which honestly is most valuable because it can fit on almost every UU team).

If Cloyster attacks without setting up:

252+ Atk Cloyster Icicle Spear (5 hits) vs. 252 HP / 252+ Def Swampert: 140-170 (34.6 - 42%) -- approx. 83.7% chance to 3HKO after Leftovers recovery
252+ Atk Cloyster Rock Blast (5 hits) vs. 252 HP / 252+ Def Swampert: 45-55 (11.1 - 13.6%) -- possibly the worst move ever
0 SpA Cloyster Hydro Pump vs. 252 HP / 0 SpD Swampert: 114-135 (28.2 - 33.4%) -- 91.9% chance to 4HKO after Leftovers recovery (assuming you can hit 4)

If Cloyster sets up:

+2 252+ Atk Cloyster Icicle Spear (5 hits) vs. 252 HP / 252+ Def Swampert: 285-335 (70.5 - 82.9%) -- guaranteed 2HKO after Leftovers recovery (which to be fair is still really scary)
+2 252+ Atk Cloyster Rock Blast (5 hits) vs. 252 HP / 252+ Def Swampert: 95-110 (23.5 - 27.2%) -- possible 5HKO after Leftovers recovery
+2 0 SpA Cloyster Hydro Pump vs. 252 HP / 0 SpD Swampert: 226-267 (55.9 - 66%) -- guaranteed 2HKO after Leftovers recovery

Swampert's main reply would be to Roar to make stat boosts useless and accrue stealth rock damage on Cloyster upon reentry, but scald can do some damage too and sometimes gets a burn which is really nice to cripple Cloyster (it outdamages earthquake since Cloyster's defense is massive and Naughty Cloyster gets wrecked)

0 SpA Swampert Scald vs. 0 HP / 0- SpD Cloyster: 78-93 (32.3 - 38.5%) -- 97.9% chance to 3HKO
0 SpA Swampert Scald vs. -1 0 HP / 0- SpD Cloyster: 118-139 (48.9 - 57.6%) -- 95.7% chance to 2HKO

So if Cloyster's weak, you can still do serious damage with just attacking (maybe it would be safer in case of a switch?).

tl;dr Swampert's great and Swampy means Cloyster can just go icicle spear itself.

 

[CoolStoryBrobat]

Late update. Top 3 Checks/Counters to Cloyster have been chosen (in no specific order):

Top 3 Counters:

Registeel - ~Volbeatdown~
Empoleon - boltsandbombers
Jellicent - The TurtleLord

Top 3 Checks:

Lucario - Dudeman130498
Metagross - imaloony
Porygon2 - Thisbemyalt

OP will be updated accordingly. Next week's victim is a highly overlooked mon that I used on one of my first half-decent teams back when Blissey wasn't a thing in UU. And just in case people tend to trip up and do this...don't reserve something and change your reservation in the event that what you reserved wasn't as effective as you thought it was, seriously. Run some basic calcs first at least...if you change your reservation it's not counting, period.

Porygon-Z @ Life Orb / Lum Berry / Silk Scarf
Ability: Adaptability
EVs: 80 HP / 252 SpA / 176 Spe
Modest Nature
- Tri Attack
- Shadow Ball
- Nasty Plot
- Agility