Although Quagsire has rather average stats, it works well in Ubers thanks to Water Absorb and an immunity to Electric-type moves. Quagsire has one main purpose in Ubers: to be one of the best Kyogre checks in the game. It doesn't do much else, but Kyogre is such a force in Ubers that Quagsire can be useful if you can find nothing else to check Kyogre. An immunity to Thunder Wave sets Quagsire apart from Latias as Kyogre may carry it, which could be devastating for Latias. Without its STAB Water moves, Kyogre is forced to use Ice Beam, which from a standard Choice Scarf Kyogre is only a 4HKO. Encore, Toxic, and Yawn give Quagsire an effective support movepool, which can be used to cause switches and inflict status on opponents. This can be extremely helpful when used in conjunction with entry hazards, such as Stealth Rock and Spikes. Quagsire's main downfall is its low offensive power. This makes it an easy Pokemon to set up against, and it's especially vulnerable to Pokémon with Taunt.
Quagsire's excellent typing, above average HP stat, and Water Absorb ability make it a solid support Pokemon in Ubers. Quagsire is an excellent counter to all Kyogre sets due to its immunity to the Water- and Electric-type moves Kyogre throws around. If Kyogre tries to set up Calm Mind or Substitute, Quagsire can cripple it with Encore and force it to switch out. However, many Kyogre use Choice items, forcing them to switch out immediately.
Encore is a staple on this set, as it allows Quagsire to cripple any Pokémon who tries to set up, like Rock Polish Groudon. Not only that, but it's also helpful because it forces Pokémon such as Kyogre to use Ice Beam repeatedly, which allows you to bring in a Pokémon who will take little damage from it. Yawn is an excellent move to force switches and rack up damage from entry hazards. Toxic can be used to wear down bulky opponents such as Groudon, Kyogre, and Wobbuffet. An attacking move isn't used on this set due to Quagsire's low offensive stats. You may consider using a Shed Shell to escape Wobbuffet, as it can Encore a status move and make them useless with Safeguard.Team Options & Additional Comments >>>
Quagsire has a few usable options; however, it lacks the space to use these moves. Sleep Talk is an option for Quagsire in Ubers, as Darkrai will inevitably put it to sleep with Dark Void, though it's better to switch in most cases. Safeguard is an option to prevent damaging status, such as Darkrai's Dark Void or Giratina's Will-O-Wisp. Earthquake may be used to hit Heatran (who shuts Quagsire down with Taunt) and Dialga super effectively, while gaining a boost from STAB. Ice Punch may be used as it will 2HKO Rayquaza, while it ensures that Quagsire isn't completely shut down by Taunt. Finally, Brick Break is an option as it allows Quagsire to break screens.
Checks and Counters
Faster Pokemon with Taunt will cause problems for Quagsire, as they will stop it from using Encore, Yawn, and Toxic. Mewtwo is one of the best options, as it can cripple Quagsire with Taunt, while setting up Calm Mind or supporting other teammates with dual screens. Mewtwo can also use Trick along with a Choice item, which will cripple Quagsire and make it easier to counter.
A simple Lum Berry will also cause problems for any Quagsire who wish to status you. Darkrai is a good example as it can switch into Yawn or Toxic and put Quagsire to sleep with Dark Void. RestTalkers such as Dialga are effective at countering Quagsire as sleep status won't cause them any problems, while poison can be Rested off. However, RestTalkers should beware of Encore as Quagsire can lock a Pokémon into Sleep Talk while it wakes up.
Shaymin-S can switch into Encore and OHKO Quagsire with Seed Flare or set up Substitute from its respectable HP stat. Any Grass-type move with a considerable amount of power behind it will cause problems for Quagsire. Latias, Latios, and Deoxys-A can all use Grass Knot to hit Quagsire with 80 Base Power, which will deal large amounts of damage due to their high offensive stats.