Chansey boasts a gigantic base 250 HP stat that, when coupled with Eviolite, allows it to be a very tanky Pokemon that is capable of becoming a powerful all-purpose special wall. Imposter allows Chansey to mimic the opponent's Pokemon while retaining its greatest assets, being its large HP stat and Eviolite boosts, allowing it to act as an all-purpose check to almost any Pokemon. Imposter also inherits the opposing Pokemon's stat changes and, when coupled with its preserved bulk, allows Chansey to be a formidable check to nearly every setup sweeper in the metagame. Therefore, Imposter Chansey puts a huge strain on teambuilding, as teams must carry checks to their own Pokemon to avoid losing multiple Pokemon or, in more extreme cases, lose the game entirely to Imposter Chansey. Additionally, this ability allows Chansey to effortlessly scout for the foe's moveset simply by switching in. Fur Coat, on the other hand, propels Chansey's middling Defense stat up to a respectable amount, allowing it to act as a sturdy mixed wall that is able to switch into many powerful Pokemon like Mega Rayquaza, Mega Diancie, and Mega Mewtwo Y.
However, due to how large of a threat Imposter Chansey is, every competent team prepares thoroughly for it, reducing its overall effectiveness. A few Pokemon, such as Mega Gengar, are capable of defeating an Imposter Chansey one-on-one through the combination of Judgment and an appropriate plate item. Should Chansey opt to use Eviolite, it will find itself unable to deal meaningful damage to those foes, considering Judgment remains a Normal-type move. Additionally, its item choices are quite limited, in that it dearly needs Eviolite's defensive boosts. This means that unlike other bulky Pokemon in Balanced Hackmons, Chansey cannot afford the luxury of choosing an alternative item such as Safety Goggles, Leftovers, or even a Z-Crystal for more flexibility, making it quite predictable in that aspect. Therefore, Chansey's defensive sets are vunerable to moves like Taunt and the ever-so-common Spore thanks to said predictability.
Most of the time Chansey inherits the moves of the Pokemon it transforms into, so the selected moves are chosen to help Chansey deal with the rare instances in which Imposter fails to activate. Fake Out is a safe means of dealing damage to the enemy and it serves to primarily deactivate the Illusion ability, as it prevents Chansey from transforming upon switching in. However, keep in mind that as it is a Normal-type move, it will fail to reveal a Ghost-type's illusion, meaning Chansey cannot transform into them without the assistance of a teammate. Additionally, Chansey can revenge kill Pokemon such as Deoxys-A and Deoxys-S that have been brought down to 1 HP thanks to Focus Sash and also aids in breaking an opposing Pokemon's Focus Sash to further aid its teammates in helping take down the troublesome Pokemon. Shore Up allows Chansey to recover its HP, meaning it can still operate as a bootleg defensive pivot should Imposter not activate. Whirlwind is used to phaze the foe should they be behind a Substitute, as that disables Imposter from operating. It also serves as a way to handle setup sweepers, as Pokemon such as Mega Rayquaza, Primal Kyogre, and Mega Gengar can very easily set up on Chansey and overpower it. King's Shield helps handle powerful physical Pokemon such as Refrigerate Kyurem-B and Aerilate Mega Rayquaza as, even with Eviolite and maximized Defense EVs, it still cannot stand up to a few powerful physical attackers. Metal Burst provides Chansey with some offensive presence. As it deals damage based on the amount of HP Chansey takes from a move that turn, it can inflict some serious damage if used correctly. Alternative move options include Parting Shot to net some momentum against Pokemon Chansey has failed to transform into. It also comes with the added benefit of ignoring Substitute, one method of preventing Imposter from activating while also forcing Magic Bounce Pokemon to switch out. Refresh could also be chosen for its ability to remove any burdening status ailments, as they carry over even when transformed. Lastly, Spectral Thief or Haze removes any stat boosts the foe may have, somewhat alleviating Chansey's big weakness to being setup fodder. This could be chosen over Whirlwind, if one forgoes that move.
Eviolite boosts Chansey's defenses both prior to and post-transformation and is the crucial element of the set, granting Chansey a lot of bulk. This is what enables it to deal with so many Pokemon one-on-one. A Bold nature is used to further boost Chansey's lackluster Defense stat, and a Calm one can be used instead to further augment Chansey's Special Defense stat. Should one opt to use Metal Burst, a Relaxed nature along with minimized Speed IVs is preferred to ensure Chansey is outsped by as many Pokemon as possible. This is because Metal Burst doesn't function when Chansey moves first because has a priority of 0.
Always keep in mind that simply bringing a Chansey to a Balanced Hackmons game puts immense pressure on the opponent, as they must utilize their offensive Pokemon precisely to avoid being swept by their own Pokemon. Another important note is that Chansey is incredibly weak in its natural form (i.e. not transformed into anything), as it cannot defend itself very well against Pokemon that can switch in and damage it heavily or use certain moves like Spore. Therefore, one should actively prevent Chansey from participating in battle untransformed as much as possible. Pivot Chansey in whenever possible to scout for the foe's set. That information could prove incredibly useful when making decisions later on in the battle. It is encouraged that one switches Chansey in on a defensive Pokemon like Registeel or Zygarde-C, as in most instances, they can do very little damage to Chansey. One might also wish to double switch Chansey in predicting an opponent's switch, as that is a good way to determine a Pokemon's set. Chansey, despite having a high HP stat and access to Eviolite, can ill afford to switch into threats repeatedly, especially if the aforementioned threats lack a recovery move, so be careful about switching it haphazardly. If they are also boosting their defensive stats through the means of Contrary V-create or Quiver Dance, Chansey can actually switch in quite safely. If it does falls low in HP, however, one can switch it in on a defensive wall like Aegislash or Registeel and utilize their own recovery moves, as often those Pokemon can do little to stop Chansey from doing so. Instead, switch Chansey in after an ally has been KOed earlier or by using an ally's slow pivot move to safely enter the battle. Thanks to Imposter's mechanics, Chansey is effective at stalling PP, as it can refresh its limited PP simply by switching out. Upon returning to battle, it will have its PP replenished, allowing it to stall once more. This gives Chansey the edge in PP stalling situations. Having said that, it can be quite dangerous switching Chansey in continuously, as the opponent could take advantage of Chansey if it has transformed into a certain Pokemon, so it is important to scout which Pokemon on the opposing team Imposter-proof the opponent's offensive Pokemon, as that can ease prediction later on in the battle and even potentially save Chansey from an unnecessarily quick self-KO. For instance, if the opponent has a strong Steel-type Pokemon such as Dialga, keep in mind that any of the remaining five Pokemon could have Magnet Pull as their ability to take advantage of an Imposter Chansey. Finally, it is encouraged that, although Shore Up is superior to every other recovery move in the game, one should not use the same recovery move on multiple Pokemon, as this leaves the player very vunerable to Imprison users that also carry Shore Up. If another ally has Shore Up in their movepool, consider swapping Shore Up for an alternative option like Heal Order.
Due to the nature of Imposter, Chansey can fit on nearly every team archetype and is very self-sufficient, so it rarely requires team support to function. Having said that, Chansey appreciates free switch-ins, which slow allies such as Registeel, Aegislash, and Mega Audino can provide with U-turn or Parting Shot. The aforementioned Pokemon are also useful for setting up entry hazards to not only deter Sturdy Shedinja, a Pokemon Chansey has a tough time beating, from switching in, but also deal some chip damage to assist in a potential counter-sweep. It also breaks any Focus Sashes that frail Pokemon like Deoxys-A commonly use to protect themselves against Imposter Chansey, as they are frail yet powerful enough to OHKO a transformed Chansey after setting up. Pokemon that can handle common Judgment users, such as Mega Gengar, Galvanize Zekrom, and Primal Groudon, make for great teammates, as Chansey cannot handle them in a one-on-one situation. These Pokemon include Yveltal and Mega Gyarados, valuable for their ability to check Mega Gengar, easily the most common user of this strategy, with ease.
Shore Up is mandatory, as it increases Chansey's longevity and allows it to make repeated switch ins in all stages of the game. It also keeps Chansey's HP topped up in order to use Metal Burst more frequently and to greater effect. Metal Burst provides some offensive presence and allows Chansey to remain functional even when inflicted by Taunt. It also deals a hefty amount of damage and isn't too detrimental, as Fur Coat Chansey can sponge hits well. Whirlwind prevents Chansey from becoming setup fodder, as Chansey can do very little against a foe using setup moves. Pokemon such as Primal Groudon, Primal Kyogre, and Mega Rayquaza would otherwise be able to very easily boost up multiple times against a Chansey. It also has no way of touching foes behind a Substitute, and as such, this move comes in handy to phaze Substitute users, as Metal Burst does not bypass Substitute. U-turn allows Chansey to safely switch, generating momentum for the team. What's important to note is that U-turn still works even when trapped by moves such as Anchor Shot and Thousand Waves, meaning that Chansey cannot be trapped and KOed very easily. Wish could be an option to consider as an alternative to Shore Up. It does not provide instant recovery, but it allows Chansey to be able to support its team by passing large HP refills. This move pairs nicely with U-turn, as Chansey is often slow enough to grant a chosen ally a free switch in, in addition to a large HP restoration. It should be noted that Chansey can be taken advantage of quite easily by an opposing Imposter Chansey if one opts to use Wish, as the foe can freely use Wish to support their own team while Fur Coat Chansey can do little in return.
Eviolite is the mandatory item, as it boosts Chansey's defensive stats by a considerable amount. A Bold nature is used to further increase Chansey's Defense even after the boosts from Fur Coat and Eviolite are applied. A Calm nature can instead be used to help Chansey against Choice Specs users while still posing a threat to physical attackers. A Relaxed nature can be used with 0 Speed IVs to minimize Chansey's Speed, which is useful for getting off a slow Baton Pass to build up momentum. Additionally, this makes it as slow as possible in order for it to be outsped by as many Pokemon as possible so as to make better use of Metal Burst.
Switch Chansey in on threats it can check, such as Mega Diancie, Zygarde-C, and Mega Rayquaza. However, one should be careful about dangerous status moves such as Spore and Taunt, as they can reduce Chansey's effectiveness heavily. One should attempt to determine if the foe carries one of those moves before blindly switching Chansey in. It also is incredibly susceptible to Knock Off, as the move rids Chansey of its precious Eviolite. Therefore, one should be cautious about switching Chansey in on Pokemon that commonly carry Knock Off, such as Yveltal and Mega Tyranitar. It is advised that you carefully scout for the moves of suspected Knock Off users such as Mega Gyarados and Mega Mewtwo X before switching Chansey in, as losing one's Eviolite can be very detrimental. Additionally, although Chansey is a sturdy physical wall, it can ill afford to switch into Balanced Hackmons' hardest hitters such as Stakeout Primal Groudon and Water Bubble Primal Kyogre. As Chansey heavily relies on its ability to help sponge physical attacks aimed at it, Mold Breaker Pokemon are especially threatening, as they simply ignore Fur Coat altogether, so ensure Chansey avoids them at all costs. In the same vein, Sunsteel Strike users are also very threatening for Chansey. Boosting physical sweepers commonly carry the move to pierce abilities such as Fur Coat, so it is advised to scout for the move on suspected physical sweepers before sending Chansey out against them.
Pokemon such as Giratina, Aegislash, and Zygarde-C form a solid defensive core with Chansey, as the former two Pokemon can handle Fighting-types that trouble Chansey, and the latter is an excellent all-purpose physically defensive wall. Additionally, these Pokemon greatly appreciate Chansey's ability to easily tank common special moves, such as Ice Beam or Blue Flare, aimed at its allies. They are all also viable users of entry hazards, which Chansey can take advantage of because it forces many switches either by simply switching in or using Whirlwind. A Magic Bounce Pokemon such as Registeel can bounce back dangerous status moves like Spore that threaten Chansey. Additionally, Chansey can do very little to prevent the foe from setting up entry hazards, so a Magic Bounce Pokemon can easily take advantage of that by switching in and reflecting it right back. This proves especially useful should the opponent have a Sturdy Shedinja, as Chansey can do literally nothing to prevent it from switching in and forcing Chansey out. As Chansey is often a prime target for Knock Off and Spore users, one can opt to use a Poison Heal user with Toxic Orb to absorb the moves; Knock Off proves useless if the ally has already activated it, and Spore is ineffective against a Pokemon already afflicted by a status ailment. Prime users of Poison Heal include Zygarde-C, Primal Kyogre, and Mega Tyranitar.
Chansey's signature item, Lucky Punch, can be used over Eviolite on its Imposter set to help it muscle past Imposter checks with powerful critical hits. Also, it comes in handy to beat setup sweepers such as Contrary users like Mega Rayquaza and Primal Kyogre if they have boosted their defenses with moves such as V-create and Quiver Dance. However, it is inconsistent and takes away from Chansey's bulk, one of its most defining and important features. If one is especially weak to Judgment sweepers such as Mega Gengar, an Earth Plate is an item worth considering on Imposter Chansey, as it turns Judgment into a Ground-type attack to hit common Judgment users hard. These include Primal Groudon, Zekrom, and the aforementioned Mega Gengar. It also can be hard to see coming, as Chansey can effectively bluff the item, as it is not clear Chansey is holding an item other than Eviolite unless it takes a hit, and quite often it is too late at that point. Choice Scarf is another item Imposter Chansey might wish to use over Eviolite, as it gives Chansey valuable Speed to help it outspeed its foe rather than having to rely on Speed ties. However, it can be easy to play around once it is revealed, and the lack of Eviolite takes away from Chansey's bulk considerably, meaning it cannot afford to switch in nearly as often. Additionally, due to its superior HP stat, Blissey makes for a better user of Choice Scarf and Imposter, but Chansey bluffs the item better. Spiky Shield is an alternative option over King's Shield to consider, as it not only protects itself from all moves, not just status moves like the latter choice, but it also inflicts a sizable amount of damage back to its foes. Additionally, it helps knock out Shedinja, a Pokemon Chansey has a lot of trouble with. However, if Shedinja opts for Protective Pads, it will remain unfazed by Spiky Shield's recoil and continue to be troublesome, so keep that in mind. Alternative abilities include Magic Bounce to rebound dangerous moves Chansey cannot otherwise handle effectively such as Spore, but Fur Coat's defensive boosts are often more valuable, and Magic Bounce is a more worthwhile ability on another Pokemon, such as Aegislash or Registeel. U-turn could be used over Baton Pass, as they provide the same benefits, but it also deals some damage. The main downside to this is that as it is a contact move, Chansey receives some hefty recoil damage if used against a Pokemon holding the Rocky Helmet item such as Registeel and Aegislash. However, you do not pass over negative side effects of certain moves such as Leech Seed and Core Enforcer if one opts for U-turn.