Arceus-Psychic's typing allows it to check all viable Psychic-types in Ubers save for Lunala. This makes it an effective countermeasure against teams built around Psychic Terrain. A Fighting resistance also lets Arceus-Psychic serve as a check to Mega Lucario. Unfortunately, Arceus-Psychic is a fundamentally flawed Arceus forme whose few benefits are completely negated by several glaring issues. Its horrible mono-Psychic typing shoulders it with awful weaknesses to Ghost- and Dark-type moves, leaving it easily beaten by extremely dangerous Pokemon such as Mega Gengar, Marshadow, and Yveltal, as well as certain Arceus formes such as Arceus-Dark and Arceus-Ghost. This typing also makes Arceus-Psychic total bait for every status condition and vulnerable to every entry hazard, especially Toxic Spikes. Arceus-Psychic's defensive vulnerabilities are exacerbated due to its extreme passivity, as its only ways of dealing with its offensive checks are Ice Beam, Judgment, which has very poor coverage, and Toxic; this makes switching into and exploiting it very easy for the vast majority of teams. These flaws combine to make Arceus-Psychic an Arceus forme that creates large defensive holes in teams and acts as a total momentum vacuum to its own team due to its dreadful offensive capabilities. Arceus-Dark is a superior choice for any team where Arceus-Psychic would even be considered, as it checks a far larger breadth of threats while preserving the ability to beat Psychic-types.
move 1: Ice Beam
move 2: Judgment
move 3: Toxic
move 4: Recover
item: Mind Plate
evs: 252 HP / 64 SpD / 192 Spe
Ice Beam OHKOes Mega Salamence and Rayquaza, preventing them from using Arceus-Psychic as setup bait. Judgment OHKOes Marshadow, Mega Blaziken, and Mega Gengar, 2HKOes Toxapex and Tentacruel, and does solid damage to Mega Lucario and Primal Groudon. Toxic is Arceus-Psychic's only way of punishing Dark-types or bulky Pokemon that would otherwise freely switch into it. Recover allows Arceus-Psychic to continue checking Psychic-types throughout a match.
192 Speed EVs alongside a Timid nature allow Arceus-Psychic to outspeed Jolly Mega Lucario. 252 HP EVs and 64 Special Defense EVs let Arceus-Psychic stand up to the special attacking Psychic-types it is intended to check.
Switch Arceus-Psychic into predicted Psychic-type moves, such as Psycho Boost from Deoxys-A and Psystrike from Mega Mewtwo Y, so it can soak them up and force the opponent to switch out. It is often best to then switch Arceus-Psychic out. Try to avoid keeping Arceus-Psychic in play for more than a few turns; if the opponent has a Dark- or Ghost-type, which they most likely will, they can easily switch into Arceus-Psychic and eliminate any momentum it has gained. If you must keep Arceus-Psychic in play, be mindful of what might switch into to it. Using Ice Beam against opportunistic Mega Salamence, Judgment against Poison-types and Pokemon it hits neutrally, and Toxic against bulkier switch-ins and Dark-types can help it contribute something to a team. Finding free turns to use Recover is difficult, so evaluate if it is worth keeping Arceus-Psychic alive or trying to do some damage with it before you expend a turn. Stall teams will often carry Pokemon that Arceus-Psychic cannot touch at all, such as Blissey, which means it will be complete dead weight; its only use against this archetype is as death fodder.
Fairy-types, such as Xerneas, Clefable, and Magearna, are absolutely required to check Dark-types, which destroy Arceus-Psychic. Clefable can also provide cleric support, making status such as burn and poison less of an issue for Arceus-Psychic. Pokemon that can break through Steel-types, such as Primal Groudon, Marshadow, and mixed Rayquaza, are also necessary for Arceus-Psychic to function, as they completely wall it. Dark-types, such as Tyranitar, Yveltal, Alolan Muk, and Darkrai, can deal with Ghost-types and ensure that Arceus-Psychic is not the team's sole answer to Psychic-types. Tyranitar and Alolan Muk bring extra utility with them in the form of Pursuit trapping, and Alolan Muk can also absorb Toxic Spikes for Arceus-Psychic. Giratina-O can Defog away Toxic Spikes and entry hazards that wear down Arceus-Psychic; however, it compounds the weakness to Ghost- and Dark-types that Arceus-Psychic brings to teams. Wallbreakers, such as Mega Lucario, Bulk Up Marshadow, and Swords Dance Primal Groudon, can take advantage of passive walls, such as Blissey, Chansey, and, in the case of Primal Groudon, Toxapex, that otherwise laugh at Arceus-Psychic.
Arceus-Psychic cannot competently perform any other role, as it is outclassed by another Arceus forme or Pokemon in every scenario. Arceus-Psychic has access to a variety of Psychic-type Z-Moves, such as Z-Calm Mind and Z-Magic Coat, but none of them make Arceus-Psychic an appealing choice for teams. Defog sets are useless due to Arceus-Psychic's terrible defensive typing. Calm Mind sets are inferior to Lunala, Mega Mewtwo Y, and other Calm Mind Arceus formes such as Arceus-Dark and Arceus-Fairy due to Arceus-Psychic's lack of power and mediocre offensive typing forcing it to rely excessively on coverage moves.
Checks and Counters
**Dark-types**: The only way Arceus-Psychic can threaten Dark-types is by trying to hit them with Toxic on the switch. Otherwise, Yveltal, Arceus-Dark, Alolan Muk, Tyranitar, Mega Tyranitar, and Darkrai can switch in liberally and do as they please. Alolan Muk and Refresh variants of Arceus-Dark are hard counters to Arceus-Psychic, as not even Toxic can perturb them.
**Ghost-types**: Lunala, Mega Gengar, Marshadow, Arceus-Ghost, and Giratina-O can break through Arceus-Psychic with their super effective STAB moves. Lunala completely walls Arceus-Psychic and uses it as setup fodder. Mega Gengar traps Arceus-Psychic with Shadow Tag, outspeeds it, and can revenge kill it. However, it cannot switch into Judgment. Marshadow can revenge kill weakened Arceus-Psychic with Spectral Thief, but it is also OHKOed by Arceus-Psychic's Judgment. Arceus-Ghost and Giratina-O are not 2HKOed by any move Arceus-Psychic opts for and can easily dispatch it with super effective STAB moves, but Giratina-O will take a hefty amount of damage if it directly switches into an attack.
**Bulky Pokemon**: Pokemon common on stall teams, such as Blissey, Mega Sableye, Chansey, and Clefable, take little damage from Arceus-Psychic's weak attacks and do not fear Toxic; Blissey, Chansey, and Clefable often carry Heal Bell, while Mega Sableye can freely switch into Arceus-Psychic due to its immunity to Judgment and Toxic.
**Most Pokemon**: Save for the Psychic-types Arceus-Psychic checks, most Pokemon in Ubers can easily deal with Arceus-Psychic. Primal Groudon and Primal Kyogre can use it as setup fodder. Facade Mega Salamence can take advantage of Toxic, but it fears Ice Beam. Arceus-Psychic's lower Speed investment compared to most offensive Arceus formes also leaves it vulnerable to being set up on, as they can shrug off its weak attacks. Geomancy and Z-Geomancy variants of Xerneas use Arceus-Psychic as setup fodder, with the latter not even minding Toxic due to it often carrying Rest.