Arceus-Bug can offensively check Mega Mewtwo Y as well as Mega Lucario and several Dark-types, such as Mega Gyarados, Darkrai, and Arceus-Dark. This, however, is the extent of its usefulness, as its gaping flaws render it impossible to justify on any serious team. Despite it possessing good resistances to Fighting- and Ground-type moves, Arceus-Bug's very common weaknesses to Fire-, Flying-, and Rock-type moves almost totally nullify any utility its defensive typing provides. This is compounded by a vulnerability to every entry hazard, especially Stealth Rock, making Arceus-Bug's typing a liability for its team. Arceus-Bug is no better offensively, as a myraid of viable Pokemon in Ubers, such as Giratina-O, Primal Groudon, Dialga, Mega Salamence, and Xerneas, take a pittance from its STAB moves. If it is to be of any use to a team, Arceus-Bug must run a Swords Dance set, as Calm Mind sets are total Ho-Oh bait while support sets are unviable due to Arceus-Bug's terrible defensive typing. Even a Swords Dance set struggles to function, however, as X-Scissor is a very weak STAB move and Savage Spin-Out can only be used once. Due to its severe flaws, Arceus-Bug offers absolutely nothing over other Swords Dance Arceus formes, such as Arceus, Arceus-Ground, and Arceus-Ghost, which all possess superior offensive typings, power, and defensive utility. Never waste your Arceus slot on this forme.
name: Swords Dance
move 1: Swords Dance
move 2: X-Scissor
move 3: Earthquake
move 4: Stone Edge
item: Buginium Z
evs: 252 Atk / 4 SpD / 252 Spe
Swords Dance boosts Arceus-Bug's Attack to functional levels. X-Scissor is Arceus-Bug's only physical STAB move, OHKOing Mega Mewtwo Y after Stealth Rock damage without a boost and OHKOing Arceus-Dark after Stealth Rock with a boost. As a Z-Move, it becomes Savage Spin-Out, which is strong enough to OHKO 252 HP Arceus formes neutral to Bug and defensive Primal Kyogre after Stealth Rock and a boost. Earthquake allows Arceus-Bug to hit Primal Groudon as well as Steel-types such as Mega Lucario and Magearna for super effective damage. Stone Edge OHKOes Ho-Oh and ensures Arceus-Bug can fight back against Mega Salamence and Yveltal.
Full investment in Attack maximizes Arceus-Bug's power, while maximum investment in Speed and a Jolly nature allow Arceus-Bug to Speed tie with other maximum Speed Arceus formes. Buginium Z allows Arceus-Bug to use Savage Spin-Out once.
Arceus-Bug should be kept for the late-game, as its ineffectiveness against bulky Pokemon makes it a liability in the early- to mid-game. In most situations, Arceus-Bug should be switched in after a teammate has fainted, as its weakness to every entry hazard and glaring vulnerability to super effective coverage moves, such as Fire Blast from Mega Mewtwo Y and Lava Plume from Primal Groudon, make directly switching Arceus-Bug into play extremely risky. However, Arceus-Bug can be freely switched into Mega Lucario and Arceus-Dark, as they cannot touch it. Against bulkier teams, Arceus-Bug should be played aggressively; its middling power means that it will struggle against them, so attempting to do as much damage as possible to support a teammate is its best course of action.
Arceus-Bug loathes every entry hazard, especially Stealth Rock, so Defog support from Giratina-O is greatly appreciated. Offensive entry hazard removers, such as Excadrill and Cloyster, can also be considered; unfortunately, using these alongside Arceus-Bug creates very large defensive holes in a team. Stealth Rock support is necessary to assist Arceus-Bug in breaking through the few Pokemon it can beat. Primal Groudon can perform this role while also serving as an effective way of dealing with Steel-types for Arceus-Bug. Primal Groudon itself threatens Arceus-Bug; Zygarde-C, Giratina-O, Mega Salamence, and defensive Primal Kyogre can deal with it. Mega Lucario can deal with the troublesome Xerneas, while Magearna can check all of Xerneas, Yveltal lacking Heat Wave, and Mega Salamence lacking Earthquake. Darkrai and Choice Scarf Lunala can break through the Ghost-types that wall Arceus-Bug. Pursuit trappers, such as Tyranitar and Alolan Muk, can perform a similar role. Defensive variants of Tyranitar are particularly useful, as they can both Pursuit trap Ghost-types and set up Stealth Rock.
Recover increases Arceus-Bug's longevity but is often a subpar option, as it deprives Arceus-Bug of an important coverage move. Extreme Speed can defeat Deoxys-A outside of Psychic Terrain and pick off severely weakened Pokemon but offers nothing in the way of coverage. Iron Tail hits Xerneas and Clefable but has no other use. Finally, Calm Mind Arceus-Bug is an even worse option than the Swords Dance set, as it is extremely weak and completely shut down by every variant of Ho-Oh.
Checks and Counters
**Ghost-types**: Arceus-Ghost resists Arceus-Bug's STAB move and takes virtually no damage from its coverage moves, rendering it total setup bait. Both Giratina and Giratina-O are physically bulky enough to shrug off Arceus-Bug's coverage moves and can either hit it with Toxic or simply phaze it with Dragon Tail. Mega Gengar traps and outspeeds Arceus-Bug, allowing it to revenge kill Arceus-Bug if it is weakened or remove it with Destiny Bond. Choice Scarf Lunala is never OHKOed by +2 X-Scissor and 2HKOes Arceus-Bug in return with Moongeist Beam, and Z-Hypnosis variants can potentially set up on Arceus-Bug. However, a boosted Savage Spin-Out will do severe damage to a healthy Lunala and will even outright OHKO it if Shadow Shield is not in effect.
**Fairy-types**: Xerneas resists X-Scissor and takes very little damage from Arceus-Bug's coverage moves. It can then boost with Geomancy and OHKO Arceus-Bug with Moonblast. Unaware Clefable totally walls Arceus-Bug, as it ignores any of Arceus-Bug's Swords Dance boosts.
**Bulky Pokemon**: Virtually anything that is physically bulky, such as Arceus-Water, defensive Primal Kyogre, Mega Sableye, Arceus-Dragon, Buzzwole, Zygarde-C, and Arceus-Ground, can withstand most of Arceus-Bug's attacks. In response, they can either cripple it with Toxic or Will-O-Wisp or just wear it down. It should be noted that no support Arceus forme neutral to Bug can switch in on a boosted Savage Spin-Out if Stealth Rock is up, however.
**Primal Groudon**: No Primal Groudon likes switching into Earthquake, especially if Arceus-Bug has boosted. Specially defensive variants of Primal Groudon that do not carry a Fire- or Rock-type move have a particularly bad matchup against Arceus-Bug. However, Primal Groudon can still take any one hit if it switches in after a teammate has fainted or as Arceus-Bug is boosting; Arceus-Bug will then either be forced out or OHKOed by a Fire- or Rock-type move if it has switched into Stealth Rock once.
**Mega Salamence**: Mega Salamence will beat Arceus-Bug if it switches in as regular Salamence and lowers its Attack with Intimidate; it can then set up on Arceus-Bug or OHKO it with Double-Edge. However, after it has Mega Evolved, Salamence cannot safely switch in on unboosted Stone Edge, especially if Stealth Rock is up.
**Steel-types**: Skarmory, Mega Scizor, Celesteela, and Shuca Berry Dialga wall Arceus-Bug and can either set up on it, respond with a super effective coverage move, or stall it out with Toxic.
**Landorus-T**: Landorus-T resists X-Scissor, is immune to Earthquake, can take a Stone Edge, and can weaken Arceus-Bug with Intimidate. It can then cleanly OHKO Arceus-Bug with Supersonic Skystrike.