Dialga is one of the very few Dragon-types that can take a support route; it is especially useful as a bulky all-around pivot. As very few Pokemon can outright OHKO Dialga, it can easily switch into an opposing Pokemon and set up Stealth Rock or just start dishing out damage. Draco Meteor packs a strong immediate punch, but if you prefer PP and consistency, Dragon Pulse is an excellent alternative STAB move. Notably, Draco Meteor allows Dialga to severely damage Groudon, as well as OHKO Reshiram and Palkia without Stealth Rock. Fire Blast rounds out the coverage; in particular, it 2HKOes most Groudon in the sun and Ferrothorn in the rain. Roar lets Dialga force switches, but if you want Dialga to phaze through Taunt instead of Substitute, Dragon Tail is a fine alternative. Thunder works best alongside Kyogre, as its Drizzle ability remedies Thunder's poor accuracy.

The given EVs ensure that Dialga is not 2HKOed by Palkia's Lustrous Orb-boosted Spacial Rend or by non-Choice Specs Kyogre's full-power Water Spout. The Special Attack EVs and Modest nature allow Dialga to OHKO Darkrai with Draco Meteor and to 2HKO most Kyogre and some Ho-Oh with Thunder. Lum Berry prevents Dialga from being put to sleep by Darkrai leads; Dialga can then severely cripple them with Thunder Wave or OHKO them with Draco Meteor. Dialga can use Toxic in the last slot to cripple walls such as Lugia, while Thunder Wave helps Dialga's offensive teammates take advantage of slower opponents.

Dialga appreciates the residual damage from Spikes and Toxic Spikes that defensive teams can provide, as it can easily shuffle opposing Pokemon around with Roar or Dragon Tail. Tentacruel can set up Toxic Spikes, while Forretress can set up both Spikes and Toxic Spikes. However, relying on Forretress to lay down that many hazards puts it under a lot of stress. Lead Deoxys-S is a good choice to set up Spikes right off the bat, and it can even forgo Stealth Rock if Dialga opts to use it. Skarmory is an excellent partner, as it can lay Spikes, completely walls Groudon barring the rare Overheat or Fire Punch, has access to a recovery move, and can use Whirlwind to force switches. Ferrothorn can switch into most Kyogre variants and set up Spikes easily. With entry hazards taken into account, Dialga needs a teammate that can block Rapid Spin. Giratina, Giratina-O, and Arceus-Ghost are the best Pokemon for the job. Giratina and Giratina-O share great type synergy with Dialga thanks to their immunity to both Ground- and Fighting-type attacks; both check Groudon as well. Dialga also resists the Dark- and Ghost-type attacks they are weak to.

In addition to hazards support, offensive teams tend to appreciate Toxic or Thunder Wave support from Dialga. Swords Dance variants of Groudon, Terrakion, and Garchomp, as well as Rayquaza, Mewtwo, and Darkrai, all appreciate opposing Choice Scarf users being paralyzed, while a Toxic-poisoned Lugia will find it difficult to wall Rock Polish Groudon and Extreme Killer Arceus. Finally, offensive Groudon appreciates Dialga's ability to batter many of its checks, such as Skarmory and Giratina.

Dialga's typing and enormous base 150 Special Attack just scream for the user to slap Choice Specs on it and click Draco Meteor whenever possible. Indeed, with its excellent bulk and typing, Dialga is the cream of the crop when it comes to the many Draco Meteor-spamming Dragon-types in the game. Draco Meteor is easily Dialga's best STAB move, and it completely decimates anything that doesn't resist it. To illustrate, it deals at least 85% to defensive Dialga. Thunder easily OHKOes Kyogre that do not invest in Special Defense, while both Fire Blast and Aura Sphere help Dialga swat aside Steel-types. Fire Blast has a chance to OHKO Ferrothorn after Stealth Rock damage even in rain, while Aura Sphere allows Dialga to 2HKO Heatran and OHKO Tyranitar after Stealth Rock. Dragon Pulse rounds out the set as a reliable STAB move.

The given EVs allow Dialga to take advantage of its excellent bulk to repeatedly switch in and dish out the pain, but an alternative spread of 4 HP / 252 SpA / 252 Spe is perfectly usable. Earth Power can OHKO Heatran, but Aura Sphere easily 2HKOes it anyway. Thunderbolt can be used in sunny weather to strike down Ho-Oh, as can Power Gem, but it is comfortably 2HKOed by Draco Meteor anyway. Choice Specs provides the power that makes this set so threatening, but if its locking effect is not appealing, Dialga can use a Life Orb as an alternative item to power up its attacks. If using Life Orb, Stealth Rock is an option in the last slot so that Dialga can act as an offensive lead. Be aware that if you're looking for a bulky attacker, Choice Specs is definitely the better option. On the other hand, a Timid nature with maximum Speed is usable if you want Dialga to Speed tie with all base 90 Pokemon.

Blissey and Chansey are the only surefire counters to Choice Specs Dialga, as Dialga lacks any reliable way of KOing the pink blobs. Arceus-Rock in sand can take a Draco Meteor--although it still won't enjoy it--and use Recover to heal off the damage. Otherwise, one will have to rely on prediction to prevent a switch-in from becoming horribly mutilated by one of Dialga's attacks. Dialga's low Speed also makes it rather susceptible to faster revenge killers packing super effective moves. Finally, the Special Attack drop Draco Meteor causes allows bulky threats such as Arceus to set up easily. Therefore, Terrakion is a good partner, as it easily scares away Blissey and Chansey, while Arceus-Rock will not enjoy taking it on either. Excadrill is also a good teammate, as it easily outspeeds Arceus-Rock in a sandstorm and buries it with its powerful Earthquake. While not sweeping in sandstorm, Excadrill is a good spinner for rain teams, which Dialga also thrives in as rain makes Thunder 100% accurate. As Dialga is weak to Fighting- and Ground-type moves, Giratina-O is an excellent partner due to its immunity to both types; as a bonus, it can also block Rapid Spin. Lugia is another defensive Pokemon that can easily switch into attacks targeted at Dialga, while Dialga has no problem switching into Thunders directed at Lugia.

Dialga's powerful wallbreaking abilities attract two other kinds of teammates, namely entry hazard setters and cleaners. With entry hazards, Dialga finds it a lot easier to break down walls. Deoxys-S is possibly the best entry hazard layer for offensive teams, while Ferrothorn, Skarmory, and Forretress can use their bulk to set up Spikes and Stealth Rock for more balanced ones. As Dialga's main attack is its Dragon STAB, it tends to lure in Steel-types and damage them heavily. This makes sweepers such as Extreme Killer Arceus, Rayquaza, Arceus-Dragon, Choice Scarf Salamence, and Garchomp much more dangerous.

Dialga's monstrous Special Attack often eclipses its deceptively dangerous base 120 Attack. With significant EV investment in both Attack and Special Attack, as well as ridiculously powerful coverage moves, it is no wonder that Dialga is one of the most difficult Pokemon to wall in the entire game. With a Life Orb equipped, Draco Meteor from 438 Special Attack will quickly crush all but pink blobs and specially defensive Steel-types. The former Pokemon can easily be defeated by Dialga's physical move of choice; both Outrage and Brick Break can 2HKO most Blissey and Chansey after Stealth Rock damage. Outrage is preferred due to its superior power and coverage, but Brick Break can be used if you do not like locking Dialga in; it also boasts the ability to hit Heatran for super effective damage. Fire Blast absolutely annihilates most Steel-types, but it does come at the price of being nerfed in rain.

Thunder can be used in the final slot to hit Steel-types and is extremely useful in the rain to smash down Kyogre. However, Bulk Up opens up many opportunities for Dialga; not only does it allow Dialga to become progressively more dangerous, but it can also be used to lure in certain threats, such as Groudon, which is the best counter to defensive Bulk Up Dialga. Groudon will readily switch into Dialga after it uses Bulk Up, only to be met with a Life Orb-boosted Draco Meteor, which will OHKO any Groudon that don't significantly invest in Special Defense and severely cripple even those that do. Bulk Up also allows Dialga to comfortably tank an unboosted Garchomp's Earthquake and OHKO in return with its Dragon-type STAB attack.

There are many ways to EV mixed Dialga, and your pick should depend on your team. The spread listed above allows Dialga to hit extremely hard both physically and specially. With maximum Attack investment, Dialga can 2HKO most Blissey and Chansey with Outrage or Brick Break, as well as OHKOing 252/0 Kyogre and Ho-Oh with Outrage. Dialga can also invest in Speed; a Hasty nature and 192 Speed EVs allow it to outspeed neutral base 95s, most notably Adamant Swords Dance Rayquaza. Keep in mind, however, that most Rayquaza run a Speed-boosting nature. Dialga can even run a spread of 4 Atk / 252 SpA / 252 Spe with a Hasty nature to Speed tie with all base 90 Pokemon. On the other hand, Dialga can drop its Speed to the absolute minimum with a spread of 120 HP / 136 Atk / 252 SpA and a Quiet nature; such a spread allows it to survive attacks such as Choice Scarf Garchomp's Earthquake and Life Orb Mewtwo's Aura Sphere and OHKO in return with Draco Meteor. Quiet Dialga is also usable on a Trick Room team and can even forgo its last move to set up the field effect itself. Another thing to consider when running Trick Room Dialga is to lower its level to 99; this allows Dialga to outspeed uninvested Scizor in Trick Room.

It is also worthy to note that Dialga is probably the best Shell Smash recipient in the game. It resists all forms of priority aside from the rare Vacuum Wave and Mach Punch and is also immune to Toxic Spikes. Should Dialga be a designated SmashPass recipient, it should fully maximize its Speed to outrun virtually everything. Gorebyss, Smeargle, and the rarer Huntail are the only Pokemon that can pass Shell Smash, but all three can do it admirably. Should Dialga receive a Shell Smash safely, your opponent should start praying to a deity for divine intervention, because not even Arceus will be able to stop it.

Life Orb is the preferred item as it allows Dialga to hit as hard as possible while keeping the ability to switch moves. Quiet Dialga can also consider Expert Belt, as it helps preserve Dialga's bulk while still allowing it to break the walls it is supposed to. An Adamant Orb can be used to bluff a Choice item, while Leftovers can help Dialga survive for even longer. Other moves, however, are generally outclassed by the options listed. Dragon Tail allows Dialga to shuffle switch-ins and is rather effective with multiple layers of entry hazards. Earthquake is a decent fourth move, as it allows Dialga to 2HKO Jirachi and OHKO Heatran; the latter can be OHKOed by Earth Power too. If your team really hates Ho-Oh, Stone Edge and Power Gem are options to clip the phoenix's wings. Again, Stealth Rock is always an option should nothing else on your team be able to set it up, but it is a big waste of Dialga's talents.

As with all wallbreakers, Dialga appreciates entry hazard support. Deoxys-S is the premier offensive Spikes setter, while Ferrothorn, Skarmory, and Forretress work very well on more balanced teams. Giratina-O easily blocks Rapid Spin and switches into attacks super effective on Dialga, while ChestoRest Giratina can spinblock while remaining a dangerous threat. As for sweepers, those that can take advantage of the holes that Dialga punches make good teammates. Extreme Killer Arceus, Rayquaza, Arceus-Dragon, Choice Scarf Salamence, and Garchomp can all take advantage of the ravaging of Steel-types. Sweepers that synergize well with Dialga are fine choices too; Mewtwo resists Fighting-type attacks, while Flying-types such as the aforementioned Rayquaza can easily capitalize on incoming Ground-type attacks.

This set takes advantage of Dialga's numerous resistances, well-distributed defensive stats, great neutral STAB coverage, and access to Bulk Up. By boosting its Attack and Defense, Dialga can power up its attacks while increasing its physical bulk. After Dialga manages to set up Bulk Up, it can be almost impenetrable on the physical side. For example, it can easily survive a Choice Band Close Combat from Terrakion and OHKO with +1 Outrage. Rest lets a weakened Dialga heal itself, while Sleep Talk enables it to remain threatening. The RestTalk combination also allows Dialga to absorb Dark Void from Darkrai. Outrage gives Dialga more power but locks Dialga in when it is used, except when selected by Sleep Talk; alternatively, Dragon Claw can be used if you want reliability instead of more PP and power.

As Dialga will be boosting its Defense via Bulk Up, maximum Special Defense helps it cushion most special attacks. Dragon Tail can be used with entry hazard support, but it is generally an inferior option as it is quite weak. Furthermore, some phazers outspeed Dialga anyway, which makes it useless. Dialga can, however, run 164 Spe EVs to outspeed uninvested Lugia. In particular, a set of Bulk Up, Dragon Tail, Earthquake, and Substitute, along with entry hazard support, puts lots of pressure on stall teams that use phazing as their main way of dealing with Bulk Up Dialga.

As sturdy as Bulk Up Dialga might be, there are still Pokemon that can break through its defenses. Groudon can easily set up alongside Dialga with Bulk Up or Swords Dance and smash it with Earthquake; Arceus-Ground can do a similar job with Calm Mind. Excadrill and Lucario both resist Outrage, can set up Swords Dance, and OHKO +1 Dialga with Earthquake and Close Combat, respectively. Sacred Sword Terrakion can 2HKO Dialga irrespective of its Defense boosts, while Outrage cannot OHKO Terrakion without Defense drops. On the special side, Reshiram OHKOes with sun- and Choice Specs-boosted Blue Flare. Arceus-Fighting can boost up with Calm Mind, take relatively little from Outrage, and 2HKO with Judgment. Heatran can use Taunt to stop Dialga from setting up or recovering and 3HKO with Flamethrower. Skarmory and Lugia can both phaze Dialga, although they cannot stop it if Dialga is the last Pokemon. Therefore, Giratina, Giratina-O, and Kyogre are excellent teammates to run alongside Dialga due to their ability to defeat these Pokemon. Arceus-Water is also a good teammate to Dialga, as it can easily take on Heatran and Reshiram and is bulky enough to deal with Lucario, Excadrill, and Terrakion.

Phazers are also significant threats to Bulk Up Dialga. As Dialga has no Attack investment, it is quite weak initially. Skarmory and Lugia have absolutely no problems forcing Dialga out with Whirlwind or Dragon Tail, unless Dialga itself is running Dragon Tail, in which case Skarmory will be forced out first. Groudon and Hippowdon take little from Outrage and can Roar Dialga out as well. Various Arceus formes, such as Arceus-Steel, have no problems taking on and phazing out Dialga. It should be noted, however, that should Dialga be the last Pokemon, it cannot be forced out, and any team lacking a win condition will be in trouble. Perish Song is probably the best win condition, as it ensures that Dialga is KOed in three turns; its most common user is defensive Arceus. Tricking Dialga a Choice Scarf also effectively neuters it; Darkrai and Mewtwo are effective users of this strategy.

Dialga's lackluster Speed can be fixed with a Choice Scarf, which allows it to reach 400 Speed. While faster Dragon-types such as Palkia and Salamence exist, Dialga's main attraction is its typing. Its resistance to Extreme Speed allows it to check Swords Dance Rayquaza and weakened Extreme Killer Arceus, though keep in mind that Draco Meteor cannot KO a healthy Arceus, and if Arceus has Recover, Dialga loses. It is also one of the revenge killers to Tail Glow Manaphy; offensive sets are OHKOed by Thunder, while bulkier ones fail to OHKO Dialga in return. Draco Meteor is the primary attack, as with Stealth Rock in play, it easily OHKOes Darkrai, Reshiram, Zekrom, Rayquaza, Arceus-Dragon, Garchomp, and unboosted Mewtwo. Thunder 2HKOes Lugia and Ho-Oh after Stealth Rock and inflicts severe damage on Kyogre. Fire Blast prevents Steel-types from switching in freely, while Aura Sphere nails Heatran and Tyranitar for super effective damage. Lastly, Dragon Pulse gives Dialga a way of dealing consistent damage.

A Modest nature is preferred so that Dialga is strong enough to revenge kill the threats it should defeat. The Speed EVs allow Dialga to outspeed neutral-natured Deoxys-A. The advantage of outspeeding Adamant Dragon Dance Rayquaza and Naive Deoxys-A might be lost, but Rayquaza generally runs a Speed-boosting nature anyway, while Deoxys-A tends to run a Rash nature. Nonetheless, Dialga can use a Timid nature and maximum Speed if outspeeding all Deoxys-A is critical; in addition, maximum Speed Dialga Speed ties with all Choice Scarf base 90s. In terms of other options, Outrage can be run in the last slot to 2HKO non-defensive variants of Calm Mind Kyogre, as well as to 2HKO Blissey after some prior damage.

Choice Scarf Dialga might be faster than most Pokemon, but it does lose to other Choice Scarf users, such as Palkia, Garchomp, Terrakion, and Darkrai, as well as Dragon Dance Rayquaza. Groudon can handle Garchomp, Terrakion, and Rayquaza most of the time, but it can be worn down due to its lack of recovery. Scizor can switch into Darkrai safely and OHKO it with U-turn or deal major damage with Bullet Punch; if Sleep Clause is activated, various Arceus formes can easily set up on it. Finally, be very cautious of Wobbuffet, as it can easily revenge kill Choice-locked Dialga.

Blissey and Chansey don't fear anything from this set. Lugia and Ho-Oh are both problematic if rain is not up, as is opposing defensive Dialga. Ferrothorn can take any attack not named Fire Blast and set up Spikes or use Leech Seed. Defensive Arceus and Groudon can take any attack; the latter can subsequently OHKO Dialga with Earthquake. Kyogre can check defensive Arceus, Ho-Oh, Lugia, and Groudon with its powerful Water-type strikes, Giratina-O can handle Groudon and set up on opponents locked into Fighting- or Ground-type moves, while Lugia covers Dialga's weaknesses and checks Choice Scarf Palkia, Choice Scarf Garchomp, and Dragon Dance Rayquaza.