Overview
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Deoxys-S is one of those Pokemon that fills a specific role and excels at it [It is neither multiple pokemon nor able to fill more than 1 specific role at once, so make sure your subject and verb are the same number ;)]. After its ban last generation, it has come back to OU and made a splash. As a suicide hazard setter, no Pokemon can match Deoxys-S in reliability;it is guaranteed to set up Stealth Rock, typically gets at least one layer of Spikes, and can choose from any number of moves to wreck potential stops to it. As a revenge killer, it takes advantage of its blistering speed and incredibly wide offensive movepool (that gives it excellent super effective coverage(redundant), making it difficult to switch into. Its Speed also makes it an amazing dual screens user (I'd argue that prankster screens could rival it, so let's not hyperbolize), with its insane Speed ensuring that screens get up, which gives (using giving means that it's Deoxys being referenced again, not the dual screens) sweepers a layer of protection against opposing threats so that they can set up. The scariest part is that your opponent never knows exactly what it's going to do until it's already too late.
However, some factors have limited Deoxys-S's abilities this generation.(Personal preference, but since you brought up it's relegation to Ubers last gen, you can tie this paragraph to the least one with that--"However, there are reasons that Deoxys-S isn't still in Ubers; perhaps the most notable is the Defog buff;. With Defog everywhere, it's become harder to preserve hazards. Thundurus has returned to OU as well, bringing with him +1 priority Taunts thanks to Prankster, which are able to stop non-Magic Coat variants from setting up hazards. with its Prankster Taunt (as it was structured, was unclear syntactically what 'with taunt' was modifying). Additionally, traditional priority moves (again linking this drawback to the last thought) from the likes of Aegislash, Azumarill, Talonflame, (Mega) Scizor, and Mega Pinsir bypass Deoxys-S's excellent Speed, limiting its abilities. Despite these deterrents, Deoxys-S's terrifying versatility and efficiency cement it as one of the best Pokemon in OU.
Dedicated Hazard Lead
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name: Dedicated Hazard Lead
move 1: Stealth Rock
move 2: Spikes
move 3: Taunt
move 4: Fire Punch / Magic Coat / Superpower
item: Focus Sash
nature: Jolly / Timid
evs: 4 HP / 252 Atk / 252 Spe
Moves
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What is perhaps Deoxys-S's flagship set aims to lead and set up hazards. Stealth Rock and Spikes are the hazards you set up, wearing down opposing teams so that powerful teammates can rip them to shreds. Taunt is obligatory to prevent opposing setup and slower Taunt. With these three moves enabling Deoxys-S to meet its goals, the last slot aims to stop potential blocks. Fire Punch OHKOes Hasty Genesect, the standard, with the given Attack investment, which could otherwise bring Deoxys-S down to its Focus Sash and put it in range of a priority move, limiting it to only Stealth Rock. Magic Coat is another solid option to stop Taunt from opposing Deoxys-S in addition to Prankster Thundurus and Sableye. Finally, Superpower can be run to fell Tyranitar, which with Crunch followed by sandstorm damage can KO Deoxys-S, limiting it to only Stealth Rock. Knock Off is a possible alternative to hit Espeon, which is otherwise a hard stop to Deoxys-S thanks to its ability, Magic Bounce. It also cripples virtually every non-Mega foe by removing its item. This has utility against Choice Scarf users like Genesect, bulky walls with Leftovers, and much more.
Set Details
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Max Attack investment lets you always 2HKO Excadrill while giving a decent chance to 2HKO physically defensive Ferrothorn (33.2%) and a high chance to OHKO 4/0 Genesect (87.5%). It also gives an 81.3% probability to OHKO max HP Tyranitar with Superpower. With Magic Coat, run a Timid nature to minimize Foul Play and confusion damage, as well as max HP because you don't need any offensive investment without an attacking move. You can run Mental Herb for the item to block Prankster Taunt, eliminating the reliance on Magic Coat for this purpose.
Usage Tips
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You generally want to lead and start laying hazards immediately. Start with Stealth Rock, as it the most disruptive hazard, and proceed to set up as many layers of Spikes ('as many as possible' or just 'set up layers') until you die. Don't do anything besides set up hazards unless absolutely required, as you never want to risk not getting up anything, which would essentially leaving you to playing 5-6 against the opponent with no advantage. It is also unwise to lead against teams that carry a potential Defog user or Rapid Spin Excadrill. When you lead and set up hazards, you give the Defog user or Excadrill the entire match to try and get rid of them; thus, you should plan to set them up at some point later in the match unless you want to waste Deoxys-S entirely.
If you carry Fire Punch, you'll want to attack against opposing Genesect, Ferrothorn, and Excadrill. With Superpower, attack against Heatran and Tyranitar. Against opposing Deoxys-S leads, you'll want to use Magic Coat if you have it to block Taunt attempts and render the opposing Deoxys-S useless.
One question that must be addressed is the difference between this and Deoxys-D (This isn't a question ;) I'd say either 'one question is why you'd use this over Deoxys-D, or 'one issue is') . Deoxys-D is bulkier and thus has the opportunity to set up more layers of hazards in some cases, and is not reliant on Focus Sash, but is vulnerable to being 2HKOed by the many faster and powerful threats. It also has low offenses, which limit its capabilities on that front. Deoxys-S boasts insane Speed, which makes it more difficult to stop from setting up hazards, and can eliminate the extremely popular Genesect, which is a major thorn in the side of Deoxys-D. Overall, Deoxys-S is better at getting up hazards immediately for offensive teams (provided the opponent lacks a Defog user), which want them up that what them as soon as possible.
Team Options
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This Deoxys-S caters toward hyper offense teams with powerful attackers that force many switches, such as Aegislash, Talonflame, and Latios, punishing the switches necessary to handle these Pokemon and wearing them down such that they can be defeated later in the match. (This sentance is long and confusing! Generally, the best way of handling complex thoughts is to cut down on secondary clauses, which make the reader have to re-read several times to make sure they are following. I'd suggest breaking it into two sentances, and restructuring the first half to remove the parenthetical thoughts--"This set caters to teams with powerful attackers like X,Y,and Z that force switches. Deoxys-S' entry hazards break the Study ability or sash on potential checks, as well as racking up free damage and sometimes even changing a 2 or 3HKO into a 1 or 2HKO." Without Pokemon like these, Deoxys-S is almost wasted. It is also wise to carry a spinblocker to ensure that your hazards aren't just spun away. Gengar doesn't exactly match up that well against the spinners (Especially Mold Breaker Excadrill), but at the very least can block Rapid Spin and still fits with the offensive motif of its team. Alternatively, offensive Trick Room Cofagrigus can be run, boasting some hit-taking ability and the power to sweep or at least dent opposing teams with after some Nasty Plot boosts [Much like a comment earlier, Nasty Plot isn't the thing denting the team ;)]. Finally, you'll want some way to counteract Defog. You can't actually block it with anything—though proper prediction and offensive pressure will help out—but you can run Bisharp, which thanks to its ability Defiant turns the evasion reduction from Defog into a +2 boost to its Attack, putting it in a position to sweep the opposing team. (Beside the obvious code garbling, I'd mention *how* prediction and pressure will help--namely by double switching as they go into their Defog user with a pokemon that can KO it if it goes for Defog)
Revenge Killer
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name: Revenge Killer
move 1: Psycho Boost
move 2: Superpower
move 3: Ice Beam
move 4: Fire Punch
item: Life Orb
nature: Naive
evs: 112 Atk / 160 SpA / 236 Spe
Moves
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This set fits the role of a revenge killer and frightening attacker with its excellent super effective coverage. Psycho Boost is the STAB move of choice, punishing switch-ins expecting an unimpressive attack or none at all from some other variant of Deoxys-S. The rest of the moves outfit Deoxys-S with the necessary coverage it needs to devastate. Superpower OHKOes Tyranitar and 2HKOes unsuspecting Blissey expecting to wall this set. Ice Beam nails Gliscor, Landorus-T, and Hippowdon, and is vital to revenge kill threats such as Latios, Dragonite, and Latios, as well as the rare Noivern. Finally, Fire Punch is run to smack Choice Scarf Genesect hard—this is necessary because it could otherwise take any hit and OHKO back with U-turn.
Set Details
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The Attack EVs enable Deoxys-S to revenge kill standard 4/0 Dragon Dance Mega Tyranitar with Superpower. The Speed EVs are enough to outrun Choice Scarf Garchomp, which you definitely want to do so you can hit it with Ice Beam before it kills you. The remaining EVs are dumped into Special Attack to pump up the power of Psycho Boost and Ice Beam. If you desire even more Special Attack investment, you can drop to 20 Attack EVs, which are enough to OHKO max HP Tyranitar with Superpower.
Usage Tips
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Deoxys-S is essentially a replacement Choice Scarf user, boasting higher Speed than many sweepers at +1. Throughout the match, you will want to bring it in to revenge kill opposing threats. You can also devastate unprepared teams with its excellent coverage, wearing down checks with attacks from teammates. If you play well with it and preserve it, this Deoxys-S is one of the best late-game cleaners in existence. Finally, although it should generally be played as a mid-game revenge killer, you can lead with it and bluff the hazard setter, surprising foes focused on trying to prevent you from getting up hazards.
Team Options
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This Deoxys-S is one of those Pokemon that doesn't really need much support. However, generally you will want some type of entry hazards—not for any particular threat, but just to wear down opposing threats since it forces so many switches. Keeping entry hazards off your side of the field is also helpful, as in conjunction with Life Orb, they can put Deoxys-S in range of priority attacks. For this role, Stealth Rock + Rapid Spin Excadrill makes an excellent partner, murdering most spinblockers and doing exactly what Deoxys-S needs it to do. Additionally, note that this Deoxys-S isn't really fit for bulkier teams, as it offers basically nothing in the way of defensive synergy, so more offensive teams are the best fit for it.
Dual Screens
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name: Dual Screens
move 1: Reflect
move 2: Light Screen
move 3: Taunt
move 4: Stealth Rock / Magic Coat
item: Light Clay
evs: 252 HP / 4 Def / 252 Spe
nature: Timid
Moves
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This set takes a different approach to supporting offensive teams—protecting setup sweepers with Reflect and Light Screen. In addition to the two screens, Taunt is mandatory to block opposing setup and slower Taunt. The last slot is basically filler. Stealth Rock can is typically preferred to provide the extra level of support the hazard brings, but Magic Coat can be run to ensure screens get up against opposing Deoxys-S and Prankster Taunt users. Knock Off is an alternative option to slaughter Espeon, which loves to lead against Deoxys-S and set up its own dual screens.
Set Details
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The EVs are simple, maximizing Deoxys-S's bulk and Speed. A Timid nature minimizes Foul Play and confusion damage, while the Light Clay ensures partners have enough turns of the screens to set up and do damage.
Usage Tips
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With this set, you will generally want to just lead and set up screens. At the point, Deoxys-S has hopefully fainted, but if it hasn't, just sac it on the third turn or switch out if the opponent is trying to stall out the turns of your screens. To set Stealth Rock, get up the screen that's going to cushion the foe's attack, set up Stealth Rock, and then set up the second screen. If you have to Taunt or Magic Coat, try and do so before you set up screens so as to maximize their longevity. Defog users are also an issue, so you may not necessarily want to lead with it lest your screens and possible Stealth Rock be immediately removed.
This set faces some competition with Deoxys-D, which can actually set up screens multiple times. However, it's nowhere near as good at getting them up immediately due to its much lower Speed, so Deoxys-S is typically preferred on the offensive teams that best utilize these screens.
Team Options
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This Deoxys-S is meant to support hyper offense teams with setup sweepers and frail, powerful attackers. Standouts include Crawdaunt, Aegislash, Swords Dance Talonflame, and Mega Lucario, but you can literally run any number of attackers and they will benefit from the screens. Mega Lucario in particular makes an excellent partner, as Deoxys-S lures out Tyranitar, which it can easily switch into, set up on it as it is forced out, and seriously damage the opposing team.
Other Options
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Deoxys-S has a ton of options at its disposal. Another potential set besides the ones listed is a lead Rain Dance setter, which can support Swift Swim users, such as Kingdra, Ludicolo, and Kabutops. Another possible option is a TrickScarf set, which can
run defensive investment thanks to its increased Speed from the Choice Scarf, in order to get up the maximum layers of Spikes possible whilst boasting the ability to cripple foes via Tricking its Choice Scarf way. With Nasty Plot, Deoxys-S could theoretically pose a decent threat as a sweeper, but it relies on the full, mixed coverage of the listed revenge killer set to deal much damage as an offensive Pokemon, and setting it up isn't easy due to Deoxys-S's rather unimpressive—though usable—defenses. Hazard lead Deoxys-S can opt to run Skill Swap, which prevents Espeon, Xatu, and Mega Absol from bouncing back its hazards.
The revenge killer set has a myriad of potential moves, though the ones listed in the actual set are generally the best and most optimal. Knock Off can be run for the utility it has in removing the items of opponents, especially crippling to Eviolite users, such as Chansey and Porygon2, and defensive Pokemon that rely on Leftovers as their only form of recovery. It is also Deoxys-S's only way to damage Aegislash substantially. Thunderbolt is an option to revenge kill Dragon Dance Gyarados; however, it falters against Mega variants where Superpower shines, hitting it much harder. Meteor Mash has a niche in enabling Deoxys-S to bypass Sylveon.
Checks and Counters
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**Priority**: Priority is the best way to take out revenge killer Deoxys-S. Physical Mega Lucario can survive a Psycho Boost and kill with the combined damage from Close Combat, Life Orb damage, and a Bullet Punch the following turn. Aegislash can KO with a Spooky Plate-boosted Shadow Sneak after Stealth Rock damage or two turns of Life Orb recoil whilst Deoxys-S struggles to do much in return. Talonflame OHKOes Deoxys-S if it has taken one turn of Life orb damage with its Choice Band Brave Bird. Azumarill KOs with Waterfall + Aqua Jet. Bisharp kills it with Sucker Punch. Since these Pokemon carry strong moves
**Prankster users**: Prankster Taunt prevents non-Magic Coat Deoxys-S from getting up any hazards. The most notable users are Thundurus and Sableye. Additionally, Prankster Thunder Wave from Thundurus cripples revenge killer Deoxys-S for good, taking away its trademark Speed, and makes setting up hazards more difficult.
**Damaging weather**: Sandstorm breaks Deoxys-S's Focus Sash. Tyranitar can Crunch it, bringing it down to its sash; the sand it brings finishes off Deoxys-S at the end of the turn, limiting it to just Stealth Rock if it lacks Superpower. Hail has the same effect, and Mega Abomasnow has a high chance to KO with Blizzard with hail damage; running Ice Shard ensures its death.
**Magic Bounce**: Espeon, Xatu, and Mega Absol bounce back Deoxys-S's hazards, rendering it basically useless. Espeon also conveniently walls all of its Life Orb-boosted attacks, while Mega Absol can KO it with a Sucker Punch.
**Hazard removal**: Excadrill, Starmie, Skarmory, Mandibuzz, Latios, and Latias can all remove Deoxys-S's hazards with either Rapid Spin or Defog. With Defog, be sure to watch out for Bisharp, a common Deoxys-S partner that can devastate your team if it comes in on a predicted Defog.
**Bulky Steel-types**: Skarmory and Ferrothorn both handle Deoxys-S's Life Orb-boosted attacks pretty well. Skarmory flat walls it and can Defog and set up Stealth Rock or Spikes given the free opportunity it gets. Physically defensive Ferrothorn can switch in to anything besides Fire Punch and even take one pretty decently in a pinch, losing about half its health and eliminating it with Gyro Ball + Iron Barbs + Life Orb recoil.
**Determining Deoxys-S's set**: When facing Deoxys-S, it is often difficult to determine which set it is running and thus combat it. If it's leading, it's either laying hazards or setting up dual screens, in most cases. When you see a Deoxys-S on the opposing team, you should lead to handle the hazard setter to ensure you don't get caught in a bad scenario. If it sets up dual screens, stalling them out with moves such as Protect and forcing Deoxys-S to switch out manually is the best you can do to limit its overall effect. If it doesn't lead, it's probably running the revenge killer set, which you can then prepare to combat. Figuring out Deoxys-S's set isn't an exact science, but it can at least help so you don't go at it blindly. Also, it's not very wise to lead with Genesect or Tyranitar against it and just attempt to attack it, as if it carries the move that dooms you, then you've just been put in a bad spot. Instead, you may want to switch out to scout for it. Alternatively, you can run a Chople Berry on Tyranitar—a good item for it anyway—and safely kill it without having to worry about dying to Superpower.