This article gives you ideas of how to use Hydreigon in battle in the Pokémon Black, Pokémon White and Pokemon B2W2 Games. It lists popular movesets used by competitive battlers, as well as a description on how to use each set to help you understand why the moves were chosen. These popular sets are usually the best to use in battle and so reading this guide will help you in your team building.
Gen 5: Overview
Hydregion is the first Specially-based pseudo-legendary to be introduced, and it is certainly a super-powered beast. With a base 105 Attack and 125 Special Attack, Hydregion is a great mixed attacker. Draco Meteors coming from that Special Attack are going to hurt even Pokemon that resist it. Its 92/90/90 Defenses and access to tormet allows Hydregion to make appearances on defensive and stall teams. It also has less exploitable weaknesses, and great resistances (the Dark/Dragon typing isn't something that many Pokemon resist). Hydregion also has access to Taunt, which allows him to mess with walls and boosters, and U-Turn which allows it be used for scouting. That being said, Hydregion's only boosting move is Cheer Up, which boosts its Attack and Special Attack one level.
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The EVs are simple enough, and the nature depends on what you want to do with U-Turn. If you don't mind reduced damage, go for Timid. However, if you want maximum damage without an Attack EV investment, go with Hasty. Since most of the attacks Hydregion resists are Special-based, Hasty is better than Naive if you want avoid reduced attack. The extra EV goes into Special Defense to deal with Downloaders like Porygon-Z. This is a great scout that mirrors Flygon. You can also pair this with other Dragons, or Pokemon that don't like physical walls.
This set is basically Specs Latias on steroids. Draco Meteor and Dragon Pulse provide double Dragon coverage. The third slot is a choice of Fire Moves, depending on whether you're looking for the accuracy of Flamethrower or the power of Fire Blast. Surf is the best move for the fourth slot, as it provides a counter to Heatran. However, Dark Pulse is a great STAB move, and can be used against bulky Ghosts like Dusknoir, and Dusclops (with the Evolution Stone). U-Turn can also be used in this slot.
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This attacker will be able to easily kill of Blissey with Draco Meteor and Outrage, and Stealth Rock damage makes the process even easier. Spikes layers can also be used in combination with U-Turn, as the constant switching with badly hurt opponents.
The EVs are designed to make Hydregion as offensive as possible while out-speeding neutral base 95 Speed Pokemon such as Impish Gliscor.
Residual Damage will be a problem in this set, much like the Special one, but this could be remedied with Rapid Spin or Wish from Starmie, Forretress, Jirachi, or Vapoeron. Even though the nature is reducing, Fire Blast will hit Steels hard enough to scare them off.
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This set could be very effective since many Pokemon only carry one move that is super-effective on Hydregion. This set also has more surprise value and less-exploitable weaknesses, even though Heatran has better Defensive stats. The coverage move depends on preference. Dark Pule is recommended, but Flamethrower can burn the opponent, and Dark Pulse can cause the opponent to flinch.
Since most of Hydregion's resistances are special, Defense needs more of a boost from the nature. Alternative EVs could invest in Speed in order to out-speed base 90 Pokemon like Lucario.
Pairing the Special Mix Hydregion with Ferrothorn or Jellicent makes a nice little Defensive core of Pokemon that compliment each other well. Adding a Fire Pokemon like Heatran, Victini, or Shandera will produce the coveted FWG core. Pokemon that can counter Heatran are good teammates as well, as Heatran can take pretty much anything Hydregion can throw at it.
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Heatran can take pretty much anything Hydregion can throw at it, making it an excellent counter.
This pokemon can pack a punch!