"Two things are infinite: the universe and the presence of Stealth Rock; and I'm not sure about the universe."
Since their inception, entry hazards have been an integral part of basically every metagame one could set foot in with the exception of doubles formats. This Trainer Tip focuses on entry hazards and their setters specifically in the environment of the UnderUsed metagame.
Stealth Rock is arguably one of the most influential moves in all of Pokemon, and for good reason. Stealth Rock deals damage to the foe based on the type effectiveness of Rock-type move on the opposing Pokemon, using 12.5% as the baseline on a neutral Pokemon. For example, as it is 2x effective against a Flying-type, it would deal 25% damage. This racks up rather fast.
Anyway, enough talk about the hazard itself, let's get down to business. In UU, there is a wide variety of Stealth Rock users at your disposal. Some of these include Cobalion, Mamoswine, Krookodile, Swampert, Empoleon, Nidoqueen, Azelf, and even the occasional Infernape. Each of these have their own advantages and disadvantages and other roles in the team. Swampert can face down powerful Fire-types, phaze, spam Scald, and set Stealth Rock; Krookodile can use Pursuit and set Stealth Rock, Nidoqueen can make Florges wish it was never born and set Stealth Rock, and Cobalion can somehow manage to set up for a sweep and use Stealth Rock on the same set! You get the picture, right? There's a Stealth Rock setter for every team out there.
The reason Stealth Rock is so influential is because it can do so much damage so quickly from Pokemon switching in. Everyone loves their Entei and Salamence and Mega Aerodactyl and Mega Beedrill, until you realize it switches in and loses a quarter of its health. Add this with other hazards, status, and repeated attacks (as weak as they may be) and you quickly find yourself down a Pokemon.
Spikes are admittedly less dominant than Stealth Rock, but still very useful for almost any team archetype. Spikes, like Stealth Rock, deal damage upon switching in. By setting one layer of Spikes, all grounded Pokemon take 12.5% damage upon switching in. This becomes 18.75% with two layers, and 25% if three layers are set up.
The main setters of Spikes in UU are Froslass, Chesnaught, Roserade, and Forretress, though Qwilfish sometimes find use on a few teams despite its RU status (never use Spikes on Cloyster please). Froslass is a suicide Spiker that only really works on offensively-inclined teams, as it uses Spikes, Taunt, Destiny Bond, and a filler move (Icy Wind or Thunder Wave) to set Spikes, try to keep the opponent from setting hazards of their own and removing the Spikes you've just set up, and try to kill the foe by using Destiny Bond. Roserade is fun because it can be either offensive or defensive, forcing out the foe with powerful Leaf Storms and Sludge Bombs and using the free turn to set Spikes, or taking a hit and setting them up. Chesnaught is famous for being a hard counter to Gyarados if it's using Spiky Shield (because having just Spikes isn't pointy enough) and being a rather solid check to a lot of Water- and Ground-types (or both if Mega Swampert :) ) in general. Forretress is the last Spikes user I'm going to talk about here, and it is a good utility Pokemon that can pivot around with Volt Switch, set up Spikes, and remove hazards too with Rapid Spin.
Spikes are good for mostly the same reasons as Stealth Rock, but what's nice is that the damage of Spikes doesn't vary as long as the foe is grounded, which for better or for worse, is most Pokemon.
Toxic Spikes poison Pokemon upon switching in if you've set up one layer, and badly poisons them if you've set up two. You can set up a third layer if you want to for whatever reason, but it doesn't do anything more, so it's a waste of a turn.
In terms of good setters, you've got Roserade, Tentacruel, Nidoqueen, and Forretress. Roserade and Forretress I've already covered as they both can set Spikes (which is what Forretress should be doing most of the time). I've also mentioned Nidoqueen as a setter of Stealth Rock, but if you already have a Stealth Rock setter on your team, Toxic Spikes never really hurt (unless your opponent has a Heracross).Tentacruel is an interesting Pokemon as it can take a hit from Fire- and Fighting-types thanks to its typing (just don't expect it to wall them all day, because it can't). It is, however, rather good at spamming Scald and can also use Rapid Spin to remove opposing hazards.
I think its pretty obvious why Toxic Spikes are a good entry hazard, but in case you were wondering, it's really good at wearing down the opposition and can force opposing defensive Pokemon to recover more often and status + Life Orb damage on offensive Pokemon makes stuff die real fast.
Sticky Web is actually probably up there with Stealth Rock for the best entry hazard in the game. What it does is lower the Speed of grounded Pokemon by one stage when switching in. It's a shame its users suck.
Okay well they're actually not that bad, there are just better Pokemon to use than Galvantula and Shuckle. Shuckle is famous for being, of all things, a suicide lead with Mental Herb and both Stealth Rock and Sticky Web (the last two moves are filler, usually Encore and Toxic, Knock Off, or the rare Infestation). However, it loses to just about every Defogger or spinner ever and can't deal any significant damage. Galvantula actually isn't horrible, just hard to fit onto a team. First of all, Focus Sash is bad on it. It's just slow enough to be susceptible to most Taunt users and can't set up Sticky Web then. What you want to use is a Life Orb set with Thunder, Bug Buzz, either Energy Ball or Giga Drain, and Sticky Web. It's best used as a special attacker with Sticky Web as a nice bonus on the side, as it's not reliable enough to make a team around it. Unfortunately, it's just outclassed by most other Electric-types because even with a Life Orb, base 97 Special Attack isn't winning it any awards as a sweeper.
Sticky Web is good on any team, as everyone likes to move first. If you can set it up, it transforms a slow wallbreaker into a fast sweeper in the blink of an eye.
In Conclusion Entry hazards are an integral part of Pokemon in any tier, so if you're trying to pick up UU, here are some good things to look out for.
Thanks for reading and I hope to see y'all again sometime!