Overview
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Dialga has been a cornerstone of Ubers play since its introduction, and this has not changed in the sixth generation XY. It is best known for its role as an extremely reliable Stealth Rock user on account of its solid defenses and an incredible type combination that affords it nine resistances and an immunity to Poison-type moves. Dialga's Steel / Dragon typing is just as spectacular offensively, especially when its base 150 Special Attack and wide movepool are taken into account. These traits establish Dialga as one of the most versatile Pokemon in the metagame and make it notoriously difficult to switch into. Aside from its average Speed, lack of reliable recovery, and weakness to common Ground-type moves, Dialga does not really have any shortcomings at all; it has the stats, movepool, and typing to find a way around every single one of its checks and counters. Unfortunately, its common attacking moves have had their Base Power reduced, (add comma) and the Steel-type has lost some defensive potency, but these are hardly not major issues. Ultimately, Dialga is a Pokemon that can pull its weight on practically any team and one that is very easy to find room for.
Defensive
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name: Defensive
move 1: Stealth Rock
move 2: Toxic
move 3: Draco Meteor
move 4: Fire Blast / Roar
ability: Pressure
item: Leftovers
evs: 248 HP / 8 SpA / 252 SpD
nature: Calm
Moves
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Dialga is one of the sturdiest Stealth Rock users in Ubers, as its typing and defenses often allow it to switch in multiple times throughout a match and to set up the entry hazard. Toxic is mainly used to cripple support Arceus formes hoping to switch in and clear the field with Defog, though it has plenty of utility against other threats as well. It also notably allows Dialga to check Electric Arceus, which is a very difficult task otherwise. Draco Meteor's high Base Power compensates for the lack of offensive EV investment, and it still OHKOes Defog Giratina-O. Fire Blast hits Steel-types super effectively, notably Defog Scizor. However, Roar can be used instead to prevent Dialga from becoming setup fodder for Pokemon that have ways of dealing with Toxic. Thunder is also an option in the last slot for Kyogre and Substitute or Taunt users such as Lugia, Ho-Oh, and Yveltal.
Set Details
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A specially defensive EV spread allows Dialga to deal with Arceus formes and various other specially based threats as effectively as it can. Speed investment is an option, as Dialga enjoys outpacing other Pokemon in the base 90 Speed tier. Additionally, an alternative EV spread of 248 HP / 56 SpA / 204 SpD with a Modest nature is viable. In exchange for some special bulk, such a spread lets Dialga hit slightly harder while retaining the ability to survive two unboosted Water Spouts or two Lustrous Orb-boosted Spacial Rends.
Usage Tips
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Take advantage of Dialga's resistances and bulk as well as its ability to threaten Defog users; it can come in multiple times throughout a match to set up Stealth Rock if needed. That said, Dialga can still be worn down easily from repeated switch-ins because it lacks recovery outside of Leftovers. Also, Dialga should not always be led with, as it will often find itself starting against the opponent's Groudon or Landorus-T. Finally, it's worth noting that defensive Dialga is a good backup check to Kyogre, especially if it runs Thunder or Roar. It can also take on Palkia decently.
Team Options
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In general, this variant of Dialga provides support for its teammates rather than as opposed to requiring support of its own. Still, many Pokemon pair well with it. Ho-Oh, Lugia, Giratina-O, Rayquaza, Landorus-T, Shaymin-S, Thundurus, Mega Charizard Y, and Flying Arceus all have remarkable defensive synergy with Dialga. Yveltal, Kyogre, Palkia, and Water Arceus can threaten Ground-types and Blaziken effectively. Lastly, Mega Gengar can trap and eliminate Pokemon that are particularly troublesome for this set due to the lack of coverage, notably Fairy-type clerics such as Sylveon and Xerneas.
Offensive
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name: Offensive
move 1: Draco Meteor
move 2: Flash Cannon
move 3: Fire Blast
move 4: Thunder / Stealth Rock
ability: Pressure
item: Life Orb / Adamant Orb
evs: 252 SpA / 4 SpD / 252 Spe
nature: Modest
Moves
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Draco Meteor is usually Dialga's go-to STAB move, and it OHKOes or severely dents anything bar Fairy-types, Steel-types, and special walls thanks to the boost from Dialga's held item. Thanks to its secondary Steel typing, Dialga can viably run Flash Cannon, which discourages Fairy-types from switching into Draco Meteor and heavily damages any that do. It also scores a super effective hit on Rock-types such as Tyranitar, Terrakion, and Rock Arceus. Fire Blast hits most Steel-types hard even after a special attack drop from Draco Meteor, particularly if a Life Orb is used. Thunder is primarily for Kyogre and Water Arceus, (add comma) but it also hits certain special walls and tanks super effectively, including Lugia and Ho-Oh. If Thunder is unappealing, Stealth Rock is an option. However, it should be noted that Dialga lacking a status move cannot reliably defeat many Arceus formes that commonly carry Defog.
Set Details
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A Modest nature used with maximum Special Attack investment allows Dialga's attacks to hit as hard as possible, while maximum Speed investment gives it the ability to at least tie with other neutral-natured Pokemon in the base 90 Speed tier. A Timid nature can be used, but this causes Dialga to miss out on several potential OHKOs, such as against Groudon. Using an Adamant Orb yields a similar drawback, but it grants Dialga much greater longevity.
Opting for an alternative EV spread of 152 HP / 252 SpA / 20 SpD / 84 Spe gives Dialga a small amount of added bulk with minimal Life Orb recoil, (remove comma) and it allows Dialga it to outspeed everything up to Pokemon with an uninvested base 100 Speed. A spread of 168 HP / 252 SpA / 4 SpD / 84 Spe should be used with an Adamant Orb.
Usage Tips
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Offensive Dialga's Draco Meteor can actually OHKO all but the bulkiest of Ground- and Fighting-types that lack a secondary Steel typing, and Dialga easily threatens the Fairy- and Steel-types that can absorb a Draco Meteor with the appropriate move. However, be careful about using Draco Meteor against specially bulky Pokemon that can capitalize on the Special Attack drop it causes, such as Ho-Oh, Lugia, Blissey, and Calm Mind users. In addition, utilize Dialga's potential to bluff a defensive set when at full HP, or as well as the potential to bluff a Choice Specs set when scoring a KO with an Adamant Orb equipped.
Team Options
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Flying-types and Levitating Ghost-types make for naturally great teammates, as they cover Dialga's two weaknesses effectively. More specifically, offensive Dialga particularly appreciates Pokemon that can deal with specially bulky foes such as Blissey and Heatran. These include strong physical attackers and powerful wallbreakers such as Landorus-T and Choice Specs Kyogre, the latter of which brings rain to patch up Thunder's accuracy. This Dialga variant also benefits greatly from entry hazard support. A single layer of Spikes or Stealth Rock can secure crucial KOs such as an OHKO on Groudon and a 2HKO on Tyranitar, while Sticky Web support allows Modest Dialga to outspeed the entire unboosted metagame outside of Deoxys-S and Naive Deoxys-A.
Choice Specs
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name: Choice Specs
move 1: Draco Meteor
move 2: Flash Cannon
move 3: Fire Blast
move 4: Thunder
ability: Pressure
item: Choice Specs
evs: 252 SpA / 4 SpD / 252 Spe
nature: Modest
Moves
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Backed by a pair of Choice Specs, Draco Meteor inflicts massive damage on nearly anything, even most Steel-types. Flash Cannon hits Fairy-types and Rock-types super effectively, and it discourages the former from switching into Dialga at all. Fire Blast provides coverage against Steel-types, while Thunder is used for Kyogre, Water Arceus, Lugia, and Ho-Oh. Dragon Pulse is a much more consistent option than Draco Meteor, but it is considerably weaker.
Set Details
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Maximizing Dialga's Special Attack stat causes its attacks to deal ludicrous amounts of damage with the boost from Choice Specs, while maximum Speed investment allows Dialga to outrun and OHKO bulkier Pokemon with a similar base Speed stat, such as support Groudon and defensive Yveltal. 168 HP / 252 SpA / 4 SpD / 84 Spe is an alternative EV spread that grants Dialga some added bulk while keeping its ability to outspeed everything up to Pokemon with an uninvested base 100 Speed intact. A Timid nature with the original EV spread is also viable in order to outpace Pokemon within the base 90-99 Speed range that commonly use a neutral Speed nature, such as Swords Dance Rayquaza.
Usage Tips
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Draco Meteor is a good move to throw out most of the time, as it deals severe damage to most Steel-types, (add comma) and Fairy-types will rarely switch in on Dialga due to the threat of Flash Cannon. However, Fairy-types become a problem once Dialga's set is revealed, as they can then switch into a predicted Draco Meteor with impunity. Be wary of special walls and Calm Mind users as well, because these Pokemon can survive a Draco Meteor and exploit the resultant Special Attack drop caused by the move. Aside from this, a Choice Specs-boosted Draco Meteor will flat out OHKO every single relevant Ground- and Fighting-type other than Fighting Arceus, Excadrill, Lucario, and Ground Arceus, and even the latter two have a chance to be OHKOed. Also, Choice Specs Dialga can safely bluff any other set while at full HP, meaning it's not a bad choice to lead with—it can easily end up OHKOing a Ground-type threat such as Groudon right off the bat.
Team Options
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Once again, Flying-types and Levitating Ghost-types make great teammates due to their defensive synergy with Dialga, while offensive juggernauts such as Mewtwo and Choice Specs Kyogre can muscle through the special walls that Dialga struggles against. A Toxic lure is also helpful for Pokemon such as Lugia, Ho-Oh, and Calm Mind users and aids Dialga in breaking past them later. This set also enjoys Sticky Web support due to Dialga's middling Speed.
Other Options
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Dialga has a ton of other options, though many have decreased in effectiveness from previous generations. A Choice Scarf set is usable and is notably effective at picking off weakened Extreme Killer Arceus. Air Balloon is another interesting item option for Dialga that is preferable to Magnet Rise due to the latter taking up a moveslot. Aura Sphere and Earth Power are alternative coverage options that can hit Heatran super effectively, but they are inferior to Fire Blast against most other Steel-types. Similarly, Stone Edge or Power Gem can be used if Ho-Oh is an issue. Thunder Wave is a good status option that can neuter faster attackers. Heal Block works wonders against walls, but it is difficult to find room for. Dialga is a good user of Trick Room and can surprise many faster switch-ins with the move. Metal Burst is another intriguing option, but it is often too unreliable to be of much use. Dragon Tail can be used to phaze, but Roar is generally safer due to the existence of Fairy-types. Rest is Dialga's only reliable recovery move. Lastly, Bulk Up is yet another interesting option that can be used on a mixed lure set for Ground-types alongside Iron Head, Draco Meteor, and Fire Blast or Outrage. It can also be used on a RestTalk mono-attacking set with Iron Head, but this is rather gimmicky and wastes Dialga's formidable special attacking potential.
Checks & Counters
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**Specially Bulky Clerics and Status Absorbers**: Dialga's standard support set is very difficult to outright counter, especially with the presence of Mega Gengar as a teammate. However, clerics such as Sylveon, Xerneas, and Blissey have no trouble against support Dialga. Specially defensive Kyogre can take on Dialga lacking Thunder. Many other specially bulky Pokemon are good answers to Dialga as well, especially if they have methods of dealing with Toxic. Heatran and defensive Mega Mewtwo Y are good examples of this.
**Ground- and Fighting-types**: Though they cannot switch in easily, Ground- and Fighting-types such as Groudon, Ground Arceus, Blaziken, and Mega Mewtwo X are capable of OHKOing Dialga with their STAB moves.
**Arceus Formes**: Almost any variant of Arceus that doesn't mind Toxic is a good answer to Dialga, including Poison Arceus and Calm Mind + Refresh Water, Dark, or Fairy Arceus.
**Ho-Oh**: Due to Regenerator, Ho-Oh doesn't mind Toxic as much as other special walls, fearing only Thunder. It can often safely set up a Substitute against Dialga or hit it hard with Sacred Fire or Earthquake.
**Anti-Leading**: Darkrai and Breloom threaten Dialga in a lead scenario, as do Pokemon that can hit it super effectively, (add comma) such as offensive Groudon.
