(insert fire related pun here)
QC 3/3 (Fireburn, Sweep, Blue Jay)
GP 2/2 (GatoDelFuego, Calm Pokemaster)
Boasting a good offensive typing that has gained a new resistance to Fairy, Fire Arceus finds itself gaining a new niche in checking all Xerneas sets, Fairy Arceus, and the Steel-types that have also seen a rise in usage in XY. Due to its unpredictability, many opponents will have trouble figuring out exactly what set Fire Arceus is running, but all of its possible sets have the same troubles: it draws Kyogre and Palkia in like a magnet while also being severely crippled by all forms of entry hazards. Fire Arceus also has trouble finding switch-in opportunities against most Ubers Pokemon, but an immunity to Will-O-Wisp can aid with this issue. While reliant on team support, Fire Arceus can pull its weight if played well.
name: Calm Mind
move 1: Judgment
move 2: Thunder
move 3: Recover
move 4: Calm Mind
item: Flame Plate
evs: 248 HP / 164 SpD / 96 Spe
Calm Mind allows Fire Arceus to make the most of its offensive capabilities, turning Fairy-types such as Xerneas and Steel-types such as Scizor into mere setup fodder. While Fire Arceus has numerous strong Fire-type moves such as Overheat and Fire Blast at its disposal, Judgment is preferred for reliable power and accuracy. Thunder has shaky accuracy but is a necessary evil to bypass Pokemon such as Ho-Oh and other Flying-types, and even Kyogre in an emergency. Recover enchances Fire Arceus's longevity and lets it continue to use Calm Mind safely. Spacial Rend is an optional move that can deal with the Dragon-types that resist the original set's moves as they resist Judgment and Thunder. Grass Knot is also a possible option, hitting Ground- and Rock-types for super effective damage while still dealing good damage to Kyogre.
248 HP EVs allow Fire Arceus to switch into Stealth Rock five possible times while retaining maximum bulk. 164 Special Defense EVs give Fire Arceus some protection against special hits such as Xerneas's Moonblast and allow it to begin using Calm Mind safely. 96 Speed EVs with a Timid Nature allow Fire Arceus to outspeed up to base 100 Speed Pokemon such as Mega Kangaskhan and Palkia. An alternative EV spread includes running maximum Special Defense with a Calm nature to give more of a safety net against special attackers, but Fire Arceus should always aim to be somewhat fast.
Fire Arceus can usually switch into the Steel-types and Fairy-types roaming the tier and begin to set up on them. As it is mainly used as an effective Xerneas check, keeping it healthy when there is a Xerneas on the opposing team is essential to have any chance of dealing with the Geomancy set. To give Fire Arceus an easier time with Geomancy Xerneas, attack the latter with another Pokemon as it sets up, or just simply switch in Fire Arceus as it uses Geomancy. If you suspect a Kyogre switch-in, use Thunder to catch it off-guard and deal good damage. Fire Arceus can actually win against Kyogre if it has already accumulated Calm Mind boosts, but this is a rare occurrence; it needs two Calm Mind boosts to live Choice Scarf Kyogre's Surf after Stealth Rock, while needing three Calm Mind boosts to successfully OHKO Kyogre with Thunder should Kyogre be holding Choice Specs instead. Status moves such as Toxic can really put a damper on Fire Arceus; watch out for them when setting up on defensively oriented Pokemon.
Having a good Kyogre check such as Palkia is mandatory if you wish to use Fire Arceus successfully. Palkia itself gives Fire Arceus a lot of trouble, and as such a teammate like Blissey is a great idea. Blissey, defensive Xerneas, and Sylveon can provide emergency cleric support for Fire Arceus should it be poisoned while also helping with the Dragon-types that the set struggles against, but they are not always necessary. Landorus-T is a great teammate as well, curbing the Ground-types like Groudon that can severely damage Fire Arceus and setting Stealth Rock to keep Ho-Oh at bay. In the same regard, Giratina-O and Gliscor can also work as Ground-type checks. Defog or Rapid Spin support is essential to stop Fire Arceus being crippled by entry hazards, but because using another Arceus to provide such support isn't possible, Scizor or Giratina-O are the only options for Defog support, while Rapid Spin users such as Tentacruel and Excadrill can also be good teammates for entry hazard removal.
Overheat is an option, and while its Special Attack drop makes this a troublesome option, it can function as an extremely powerful hit-and-run move with sun support. Fire Blast is slightly more powerful than Judgment but has lower PP and reduced accuracy, leaving it a sub-par option. Roar can guarantee that Fire Arceus will always remove the threat of a boosted Geomancy Xerneas and annoy other setup sweepers. A set used specifically for luring in specific threats and taking them out is an option thanks to Fire Arceus's great coverage options and unpredictability. The set can consist of Grass Knot, Overheat, Stone Edge, and Spacial Rend or Earthquake, with the EV spread being 72 Atk / 224 SpA / 212 Spe with a Rash nature to ensure that the moves take out their intended targets. Overheat from this set OHKOes Groudon in sun and Mega Gengar in neutral weather, while also doing considerable damage to the Pokemon the other moves don't cover, such as Xerneas and Yveltal. Grass Knot hits Kyogre, Gastrodon, and Quagsire for heavy damage, while Stone Edge has a considerably high chance to OHKO Ho-Oh. Spacial Rend hits Dragon-types hard, and Earthquake OHKOes Heatran after Stealth Rock damage. Other options worth a mention for Fire Arceus include Ice Beam, to hit the Dragon- and Flying-types that resist Judgment, but it is rather weak without multiple Calm Mind boosts. Stone Edge can be used for dealing more damage to Ho-Oh. Status moves can also work, as Fire Arceus's unpredictability can easily force switches.
Checks & Counters
**Kyogre** : Being able to switch in on any move barring a boosted Thunder, all Kyogre variants can easily switch in and destroy Fire Arceus with rain-boosted Water-type moves.
**Other Arceus Formes** : Other Arceus formes, namely Dragon, Rock, Ground, and Water, can switch in and threaten with their STAB moves or begin setting up on Fire Arceus. Extreme Killer Arceus can also revenge kill with Earthquake.
**Palkia** : 4x resisting Fire Arceus's STAB attacks and taking little damage from any other unboosted move, Palkia can switch in, Toxic Fire Arceus, and then whittle it down with its own STAB attacks. Palkia isn't as big of an issue if Fire Arceus is running Spacial Rend, however.
**Ho-Oh** : Without Stealth Rock in play, Ho-Oh can easily tank any attack Fire Arceus throws at it and potentially overwhelm it with its own STAB attacks or even Earthquake, should Ho-Oh be running it.
**Dragon Types** : Many Dragon-types used in Ubers resist Fire- and Electric-type moves, and should Fire Arceus not have Spacial Rend, Dragon-types can be very troublesome, as they can take Judgment and Thunder easily and either status or hit Fire Arceus very hard. Examples include Zekrom, Reshiram, Giratina, Giratina-O, and Dragon Arceus.
**Blissey** : With its astounding special bulk, Blissey can handle even boosted hits from Fire Arceus and stall it out with Toxic.
**Tyranitar** : Due to its Fire resistance and boosted Special Defense in the sand, Tyranitar can take Fire Arceus's attacks easily and threaten to KO with Stone Edge.
**Heatran** : Immune to Fire Arceus's STAB and taking little damage from unboosted Thunder, Heatran can Toxic Fire Arceus, set up Stealth Rock, then phaze it out.
**Mega Blaziken** : Being able to handle at least one boosted attack from Fire Arceus, Mega Blaziken can set up a Swords Dance and OHKO with Low Kick.
**Trappers** : Pokemon such as Wobbuffett, Mega Gengar, and Gothitelle can trap Fire Arceus and either take it out or leave it as setup fodder for other Pokemon.
**Toxic** : Common in the Ubers metagame, Toxic will put Fire Arceus on a timer and limit its sweeping potential should it not have cleric support.
**Entry Hazards** : Because Fire Arceus is susceptible to all entry hazards, setting these up and forcing Fire Arceus out can really rack up damage and limit its switch-in opportunities.
**Revenge Killing** : While Fire Arceus may be able to outspeed most of the Ubers tier, faster Pokemon such as Deoxys, Mewtwo, Mega Gengar, and Choice Scarf users can pick it off should it be weakened.