A Guide to Entry Hazards in OU

Stealth Rock

The user lays a trap of levitating stones around the opposing team. The trap hurts opposing Pokémon that switch into battle.
PP: 32
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Stealth Rock is easily the best hazard in the metagame, which is evidenced by the fact that it is considered mandatory by a portion of the playerbase. This is because Stealth Rock does fixed damage to every Pokémon that switches in; how much damage they take depends on their typing. Stealth Rock aids many wallbreakers to break through the opposing team.

Heatran

Heatran @ Steelium Z
Ability: Flash Fire
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
- Lava Plume / Magma Storm
- Earth Power
- Flash Cannon
- Stealth Rock

Heatran is arguably the best Stealth Rock setter in OU thanks to its ability to pressure common hazard removers such as Tornadus-T, Tapu Koko, Zapdos, and, notably, Mega Sableye, which means it can usually manage to set Stealth Rock up and keep it up against stall, excluding Moltres variants. Heatran forces many switches against passive Pokémon in fear of getting trapped by Magma Storm, which gives it ample opportunities to set Stealth Rock. Its typing also grants it a good number of opportunities to switch into battle, most notably having a resistance to Fairy-, Steel-, and Flying-type moves from Pokémon like Clefable, Celesteela, Ferrothorn, and Tornadus-T. However, Heatran lacks recovery outside of Leftovers, which leads to it being worn down quite fast. Heatran pairs very well with Tapu Bulu, which can switch into Ground- and Water-types like Landorus-T, Zygarde, and Ash-Greninja, which can try to take advantage of Heatran. Its Grassy Terrain also provides Heatran with additional recovery and weakens Earthquake.

Landorus-T

Landorus-Therian @ Flyinium Z / Rockium Z
Ability: Intimidate
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Stealth Rock
- Earthquake
- Fly / Stone Edge
- Swords Dance

Landorus-T is one of the best Pokémon and Stealth Rock setters in the tier thanks to its versatility, efficiency, and ability to pressure every viable Defogger in the meta with the right set. Due to its offensive prowess, it forces many switches, which gives it a ton of opportunities to set up Stealth Rock. Landorus-T is often found on hyper offensive teams as a suicide lead because it usually manages to keep Stealth Rock up thanks to its ability to pressure all Defoggers and also keeps momentum up. Landorus-T is also an excellent defensive pivot capable of checking many physical attackers in the tier, such as Zygarde and Mega Lopunny, and forcing these Pokémon out to get a good number of opportunities to set Stealth Rock. Pokémon such as Ash-Greninja and Zygarde appreciate Landorus-T's ability to lure and remove defensive Grass-types. Other suicide leads such as Tapu Koko and Greninja appreciate Landorus-T's ability to set Stealth Rock reliably and keep momentum up. Mega Mawile pairs incredibly well with Landorus-T as well, because it appreciates Stealth Rock support and free switches via U-turn. Landorus-T offers a good Ground-type check for Magearna, and in return Magearna provides a check to Tapu Lele and Clefable.

Mega Tyranitar

Tyranitar @ Tyranitarite
Ability: Sand Stream
EVs: 168 HP / 252 Atk / 88 Spe
Adamant Nature
- Stealth Rock
- Pursuit
- Stone Edge / Crunch
- Earthquake / Fire Punch

Mega Tyranitar manages to win a lot of hazard wars thanks to its ability to pressures other common Stealth Rock setters. Thanks to Mega Tyranitar's offensive and defensive presence, it beats most of the common Defoggers in the tier, such as Tornadus-T and Zapdos, as well, and its offensive prowess lets it force many switches, which gives it many opportunities to set Stealth Rock up. Its great bulk and typing allow it to check Psychic-types such as Mega Latios, Mega Latias, and Choice-locked Tapu Lele as well as Ghost-types such as Blacephalon and Gengar. Mega Tyranitar usually manages to set Stealth Rock up against stall teams thanks to its ability to pressure Mega Sableye and other common Defoggers on the archetype, such as Zapdos and Moltres. Tapu Bulu checks Water- and Fighting-types such as Ash-Greninja, Mega Medicham, and Mega Lopunny, which Mega Tyranitar struggles against. It also provides Mega Tyranitar with recovery and weakens Earthquake. Excadrill appreciates Mega Tyranitar's sand, which allows it to sweep with Sand Rush, and provides Rapid Spin support.

Clefable

Clefable @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
- Moonblast
- Soft-Boiled
- Stealth Rock
- Thunder Wave / Ice Beam / Calm Mind / Knock Off / Wish

Clefable is a decent Stealth Rock setter because it's able to force many switches against passive Pokémon, which gives it ample opportunities to set up Stealth Rock, and it can pressure common Defoggers such as Tornadus-T, Zapdos, and Mega Sableye. Clefable's typing and all-around okay stats allow it to check and force out staples such as Zygarde and Mega Lopunny, increasing the number of opportunities it gets to set Stealth Rock even further. A wide movepool gives Clefable many different options to use, such as Thunder Wave, Ice Beam, Calm Mind, and Knock Off, which can each allow Clefable to pressure out even more Pokémon. Clefable pairs well with Pokémon that pressure Steel-types, such as Heatran and Magnezone. They appreciate Clefable's ability to check common Ground-types such as Zygarde and Gliscor.

Spikes

The user lays a trap of spikes at the opposing team's feet. The trap hurts Pokémon that switch into battle.
PP: 32
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Spikes is very similar to Stealth Rock, as it also does fixed damage upon switch in; while it is not considered mandatory, it is still very prominent in the metagame, as users of the move are very easy to fit on teams. Spikes differs itself from Stealth Rock with the fact that it can be stacked up to 3 layers. While fat Steel-types such as Magearna, Ferrothorn, and Heatran aren't bothered much by Stealth Rock and are immune to Toxic Spikes, they are susceptible to Spikes due to their lack of reliable recovery. Similar to Stealth Rock, Spikes aids wallbreakers to break down walls much more easily.

Ash-Greninja

Greninja-Ash @ Choice Specs / Waterium Z
Ability: Battle Bond
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Hydro Pump
- Dark Pulse
- Water Shuriken
- Spikes

Ash-Greninja is an amazing user of Spikes thanks to its ability to force many switches against common Pokémon such as Heatran and Mega Latios, which it can use as an opportunity to set Spikes. Spikes also punishes common defensive answers such as Toxapex, Ferrothorn, Tangrowth, and Assault Vest Magearna, which usually attempt to switch into Ash-Greninja, and can potentially put them in 2HKO range. Similar to Heatran, Ash-Greninja also pressures common Defoggers such as Tornadus-T and Landorus-T, which lets it keep up Spikes reliably. The only two Defoggers that are capable of Defogging in front of Ash-Greninja are Tapu Fini and Mega Altaria, which are rather uncommon. Pokémon such as Mega Mawile and Mega Scizor pair well with Ash-Greninja because Spikes can consistently wear down Pokémon like Heatran, which Mega Mawile and Mega Scizor usually manage to force in.

Greninja

Greninja @ Waterium Z
Ability: Protean
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Spikes
- Hydro Pump
- Ice Beam
- Hidden Power Fire

Greninja is a good Spikes setter thanks to its Speed and unpredictability, which ultimately let it force many switches and secure many opportunities to set up Spikes. Greninja pressures Defoggers incredibly well thanks to its access to many coverage moves that will be backed up by STAB thanks to Protean, which means it can manage to keep up Spikes usually. Thanks to its high Speed and access to Taunt, Greninja also excels at being a lead. Greninja fits best on balance and bulky offense teams, where it's commonly paired with Pokémon such as Zygarde and Mega Mawile to wear down conventional checks. It's also found on hyper offensive teams as a lead to set up Spikes and to support Pokémon such as Magearna, Zygarde, and Hawlucha.

Ferrothorn

Ferrothorn @ Leftovers
Ability: Iron Barbs
EVs: 252 HP / 92 Def / 164 SpD
IVs: 0 Spe
Sassy Nature
- Spikes
- Leech Seed
- Power Whip
- Gyro Ball / Knock Off / Protect

Ferrothorn is the premier Spikes setter for any defensive team that seeks a bulky Steel-type that can also set Spikes. Its great bulk allows it to check and force out prominent Pokémon such as Tapu Koko, Ash-Greninja, and Mega Latios, which means it has more than enough opportunities to set Spikes. Ferrothorn's strong Gyro Ball also allows it to pressure common Defoggers such as Tornadus-T and Tapu Koko. It also has access to Knock Off and Leech Seed, which let it harass Pokémon like Heatran, Celesteela, and Chansey. Ferrothorn is an incredible teammate to Mega Alakazam and Gliscor because Spikes consistently wear down their checks. They check Heatran in return, which is one of the most common checks to Ferrothorn.

Toxic Spikes

The user lays a trap of poison spikes at the feet of the opposing team. The spikes will poison opposing Pokémon that switch into battle.
PP: 32
Type:
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Toxic Spikes isn't very common in the tier due to its poor distribution, but it is still amazing, as it can punish Pokémon very heavily. Similar to Spikes, Toxic Spikes can be stacked, but only up to 2 layers. It also doesn't affect Flying-types or Pokémon with Levitate, just like Spikes. However, unlike Spikes or Stealth Rock, Toxic Spikes doesn't deal fixed damage upon switch in. Instead, it poisons the foe upon switch in. Toxic Spikes is more suited to make Pokémon such as Tangrowth and Gastrodon think twice about switching in, because they lack any way to get rid of poison.

Toxapex

Toxapex @ Black Sludge
Ability: Regenerator
EVs: 248 HP / 8 Def / 252 SpD
Calm Nature
- Scald
- Haze
- Recover
- Toxic Spikes

Toxapex is the best Toxic Spikes user OU has to offer, as its incredible bulk, great defensive typing, and access to reliable recovery allow it to consistently force out common threats such as Ash-Greninja, Greninja, and Mega Scizor. Thanks to the number of switches Toxapex forces, it can often set up Toxic Spikes. While Toxapex can't offensively pressure common Defoggers like Tornadus-T and Tapu Koko, it can somewhat pressure them with Scald burns. Toxapex is a great partner to Zygarde and Reuniclus because Toxic Spikes cripples common checks, which lets Zygarde or Reuniclus overwhelm them.

Sticky Web

The user weaves a sticky net around the opposing team, which lowers their Speed stat upon switching into battle.
PP: 32
Type:
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Sticky Web isn't really comparable to any other entry hazard, as it doesn't deal fixed damage or inflict a status ailment upon switch in. Sticky Web is very niche because a whole team has to revolve around the move to make it work; the sole reason to use it is to give strong Pokémon with middling Speed, such as Mega Pinsir and Mega Medicham, the ability to outspeed many Pokémon they otherwise can't, which makes it very hard to stop them.

Araquanid

Araquanid @ Focus Sash
Ability: Water Bubble
EVs: 216 HP / 252 Atk / 40 SpA
Brave / Adamant Nature
- Sticky Web
- Liquidation
- Magic Coat
- Hidden Power Fire / Toxic

Araquanid is a reliable setter for Sticky Web teams, as despite its low Speed stat, it excels at pressuring common Defoggers thanks to its access to Magic Coat and Water Bubble-boosted Liquidation. Because of its ability to pressure common Defoggers, it pairs well with Pokémon that take advantage of Sticky Web's Speed drops, such as Mega Medicham, Mega Pinsir, and Kartana.

Ribombee

Ribombee @ Focus Sash
Ability: Shield Dust
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Sticky Web
- Moonblast
- Hidden Power Fire
- Stun Spore / Quiver Dance

Thanks to Ribombee's solid Speed stat and good utility options, it's a formidable option as a dedicated lead for teams that revolve around Sticky Web. Ribombee sits at a good Speed tier of 381, which notably allows it to outspeed Tornadus-T, which lets it keep up Sticky Web against many teams. Furthermore, its ability Shield Dust makes Ribombee immune to Fake Out flinches from Mega Lopunny and Mega Medicham, allowing it to reliably take care of these Pokémon. Access to Stun Spore allows Ribombee to cripple common threats such as Heatran and Tornadus-T. It also has access to Quiver Dance, which lets it pose a threat to common faster or bulky Defoggers such as Tapu Koko, Zapdos, and Mew. Pokémon such as Mega Medicham, Mega Pinsir, and Blacephalon are good teammates to take advantage of Sticky Web's Speed drop.