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[[quoteright:350:[[VideoGame/ChronoTrigger http://static.tvtropes.org/pmwiki/pub/images/MagusBarrier5_2687.png]]]]
[[caption-width-right:350:Aww, not again! (if he changes to Fire, we're really hosed! I knew I should've brought [[PlayingWithFire Lucca]]!)]]

A type of boss, typically in an RPG, who doesn't have a fixed place in the game's TacticalRockPaperScissors lineup, who uses a special technique or ability to periodically shuffle his elemental weaknesses, in order to keep the player guessing. The boss is also usually a powerful spellcaster (implying that his special barrier-change technique is a high-level boss ability), and often has a significant role in the surrounding story.

It may or may not be possible to use an EnemyScan on this type of boss -- even if the scan does tell you his weakness, that will be subject to change in a few turns when he changes it again (assuming the boss doesn't react to your scan by changing his weakness immediately). On the other hand, sometimes you can quickly identify the boss's current weakness -- sometimes the invocation will explicitly tell you which element to use, or the current weakness may be ColorCodedForYourConvenience (e.g. if the boss has DeflectorShields). In some cases, smart players can just use an InfinityPlusOneElement attack that [[CuttingTheKnot spares them from having to keep up with the boss's rotating weaknesses]].

[[folder:Action Adventure]]
* Every boss in the ''WesternAnimation/BuzzLightyearOfStarCommand'' [[VideoGame game]] has layers of force fields, each one that can only be destroyed by a specific weapon. (For instance, a blue shield will only be vulnerable to the Arc Laser.)
* ''VideoGame/DistortedTravesty'' likes this kind of boss. We have the Quick Time Distorter, the Data Collector, the Garbage Tracker, the Virus Core... in a twist, you usually have to hit it with whatever element it is currently using, rather than which one you think it'd be weak to (although there are exceptions).
* The eponymous final boss in ''VideoGame/MetroidPrime'', in its first form, is only weak to the sort of attacks it's using at the time. In later stages of the battle with this form, it'll occasionally switch, and then immediately switch ''again'', sometimes back to the weakness/attack setup it had before, trying to trick you into having the wrong beam ready.
** A rather bizarre semi-example from the same boss: Its second form is able to become imperceptible to all but one of your three visors. Unlike most of these examples, however, there is a set cycle as to which visor can see it.
** The final form of the Emperor Ing in ''Metroid Prime 2: Echoes'' alternates between becoming invulnerable to dark energy, light energy, and "neutral" energy (the Power Beam). The former two can be thwarted with the Annihilator Beam, which covers both elements, but burns both kinds of ammo (which you're probably quite low on [[MarathonBoss at this point]]).
** Gorea's first form from ''Metroid Prime: Hunters'' does this. Just like with Metroid Prime's core essence, there's a set pattern to what you should shoot him with. However, no matter the color of his armor, he's always weak to the Power Beam and missiles. [[spoiler:Unless you get the TrueFinalBoss part of the fight...]]
* The FinalBoss of the first ''VideoGame/{{Overlord}}'' game does this every so often. The color of his shield matches that of the Minion type needed to break through it.

[[folder:Beat 'Em Up]]
* The final boss of ''VideoGame/CastleCrashers'' uses this tactic in one of several forms. However, he also not only transfers the damage the wrong attack did to you, he also makes it harder for the attack that would do the proper damage hard to do.

[[folder:First Person Shooter]]
* In ''VideoGame/{{BioShock|1}}'', the final boss [[spoiler:Frank Fontaine]] supercharges himself with "ADAM" (the game's genetic version of 'magic'), giving him various powers over [[FireIceLightning fire, ice, and electricity]], teleportation, etc. His body glows with a different colour depending on the power he's using: [[color:red:red]] for fire, [[color:blue:blue]] for ice, white for electricity. Since you also get [[FireIceLightning fire/ice/electricity powers]] through using ADAM, plus an artificial version of these elemental weapons with your chemical-thrower, guess which powers he is resistant to depending on the colour he gives off and which he is weak against?
* [[spoiler:Bloodwing]] in ''VideoGame/{{Borderlands 2}}''. She switches elemental powers after taking certain amounts of damage, and is immune to whatever elemental power she is currently using. Throughout the battle, Handsome Jack says she can use all the elements, but he keeps forgetting what one of them is. [[spoiler:He then "[[KickTheDog remembers]]" once the battle is over: [[ActionBomb explosive]].]]
** The player themself can become one with an Adaptive shield, which makes the player resistant to the last damage type they took.
* ''VideoGame/TeamFortress2'': The Vaccinator reduces 10% of damage from a single damage type (fire, explosive, or bullets), both for the medic and his patient. His Übercharge increases the resistance up to 75% for the patient and recovers a small amount of that damage for the Medic.
* ''VideoGame/{{Destiny}}'': The Court of Oryx Boss Vorlog will change his shields element type as they are depleted.
* The ''VideoGame/StarTrekEliteForce'' game introduces a weapon that gets around this with the Borg: the Infinity Modulator, which [[spoiler: can randomly switch to an infinite number of frequencies and infinite number of times.]] It's the only weapon that consistently works against the Borg; they adapt to all others with enough shots.

[[folder:Massively Multiplayer Online Role Playing Game]]
* Guardian Aegis from the King's Relic dungeon in ''VideoGame/DungeonFighterOnline'' is a Barrier Changing Miniboss, that has a barrier that switches between blocking physical and magical attacks.
* Number 024 returns as Number XXIV (see the ''Final Fantasy VI'' example below) in ''VideoGame/FinalFantasyXIV'', as a miniboss in one of the later dungeons. He switches to control of ''two'' elements at once, and the players must switch to the third in order to deal him any reasonable damage.
* In VideoGame/KingdomOfLoathing, Mother Slime at the bottom of the Slime Tube doesn't technically ''change'' her resistance, but every 500 points of damage from a certain element (or lack thereof), she mutates a defense against that type of attack for the remainder of the fight. She has just shy of 3000 hit points. There are five elements in the game, plus one for non-elemental physical damage. There is a reward for defeating her without triggering any of her defense mutations.
** There's also [[spoiler:Dad Sea Monkee]], the final boss of [[BonusDungeon The Sea]]. He becomes immune to all but one type of damage each round, the cycle of which is [[GuideDangIt vaguely hinted at in his description]].
* ''VideoGame/PhantasyStarUniverse'' has the Kagajibari. Boss of the mission [[MeaningfulName "Rainbow Beast"]], he switches element to whatever element just hit him. He casts spells accordingly. His default type is [[LightIsNotGood Light]], so one would cast dark spells at him... [[ShmuckBait right?]] If you cast dark spells at him, he casts [[OneHitKill Megid]] at you.
* ''VideoGame/RuneScape'' has Dagannoth and Gelatinnoth Mothers, who change color depending if they're weak to air, earth, water, or fire spells, ranged attacks, or special and melee damage.
** In addition, there are Tormented Demons and the Dungeoneering boss Astea Frostweb, who switch protection prayers periodically. Also, the Kalphite Queen has two forms, each of which have certain resistances (even though they appear as protection prayers, the Queen can still be hurt by those types of attacks, though it counts as if the Queen had insanely high defence in those attack types, so hits happen very seldom, even if for high damage).
** Players can (and will) invert this; with prayers, you can block the three attack types. However, to avoid completely breaking the game, you can only have one protection prayer (melee, magic, or ranged) active at a time. Much of the high level content requires players to swap protection prayers to block enemy attacks.
* In ''VideoGame/WorldOfWarcraft'', while not any bosses (unless they've been forgotten), there are several types of enemies which become more resistant to magic types they've been struck with. The death knight talent Acclimation also makes causes them to develop greater magical resistance for each time that kind of energy strikes them. There isn't a corresponding weakness however, so being struck by multiple types of magic just makes the effect stronger.
** Chromaggus, the gigantic Draekadon (two-headed dragon-like Core Hound), second-to-last boss of Blackwing Lair, will change his resistances and weakness to elemental damage during the fight. When he shimmers, they change: he'll be weak to one type and nearly immune to the rest. It changes every so often, so players have to keep on their toes.

* In ''VideoGame/Kirby64TheCrystalShards'', Miracle Matter has a form mimicking each of Kirby's copy abilities in that game, and each form is only vulnerable to its own type of damage, whether by spitting back its projectiles or using the ability copied from those projectiles. Its intermediary form is completely invulnerable but also doesn't move or attack.
* ''Franchise/SonicTheHedgehog'':
** The FinalBoss of ''VideoGame/SonicTheHedgehog2006'' forces you to switch hedgehogs when it stops taking damage from high speed rams/chaos spears/telekinetic rocks. There is always a set order of which hedgehog can damage him: Silver, then Shadow, then Sonic.
** Metal Madness, the penultimate boss from ''VideoGame/SonicHeroes'' has this as well.
* ''Videogame/{{Guacamelee}}'' has the first phase of the [[BigBad Carlos Calaca]] fight. During this phase, Calaca is surrounded by different colored barriers and can only be damaged by attacks corresponding to said colors. The fact that he also [[DualWorldGameplay switches dimensions]] between attacks complicates things further.
* In ''Videogame/MegaManPoweredUp'', both Copy Man and [[spoiler:Wily]] are subjective to this. In both cases, they randomly switch between the powers of the game's Robot Masters, and, at that point, are weak to the same weapon the respective boss is.

[[folder:Role Playing Games]]
* Tarvos the Avenger in ''[[VideoGame/DotHackR1Games .hack//Quarantine]]''. Fortunately, the game tells you what, if anything, every enemy you face is tolerant (immune) to by way of glowing orange text next to its lifebar.
** On that note is the recurring boss within The World itself: The One Sin. Rumored to be very, very powerful, it can only be damaged by an element that is opposite itself when it fights. The last person who defeated it was Balmung; his unique angel-like look is the prize for defeating it. Apparently it was so powerful a semi-famous player poet composed a poem and gave Balmung (and Orca) nicknames "Descendants of Fianna" and it stuck.
** The One Sin makes a gameplay appearance in ''[[VideoGame/DotHackGU .hack//G.U. Reminisce]]''. True to its name, it can only be hurt by elements opposite of its color, and even then, you need to defeat its two shields before it momentarily opens up to reveal the core. An even nastier variant, The One Godeater, appears in .hack//G.U. Redemption. Now, it only responds to either Darkness or Light spells. This narrows down to two elements, but the boss itself is [[HarderThanHard very, very hard]] even with that advantage.
* The BonusBoss Nightmare in ''VideoGame/AlterAila Genesis'', 150% damage for a specific element. 1% for everything else
* Inverted in ''VideoGame/{{Arcana}}'', where the elemental spirits on your side each possess a cheap spell for doing this to ''your party''.
* The Chromatic Fiend in ''VideoGame/BaldursGateIIThroneOfBhaal'' does this.
** The first form of the final boss does this as well. It will actually notify players, though; first by using a high level spell of that element to signify it's about to change, and then by changing colors to match its element.
* ''VideoGame/BatenKaitos''' final boss followed this trope. Though, it showed you what element he was changing into with Seal of Entropy, and by displaying the game's icon for the element slide over his limbs, into his chest, you only have a "deck" of cards that explain your weapon usage. So you can't really specialize in all elements, or choose any particular attack that would defeat his element quickly, but instead have each of your team special in three or four elements (Chrono or Wind, Fire or Water, Light or Dark) or pack yourself full of non-element based cards and drag the fight out for a good hour or so. Fortunately, three specific characters actually specialize in those very combinations [[spoiler:(Kalas has Chrono/Wind, Sayna has Fire/Water, and Lyude has Light/Dark)]].
* The Tyrant Dragon from ''VideoGame/BreathOfFireIV'' switches between earth, wind, and water every turn.
* ''VideoGame/ChronoTrigger''
** The TropeNamer is the move Barrier Change used by Magus. This fight is the most famous example of this trope. Magus was in fact ''healed'' by ElementalPowers which did not match the element of his barrier, and changing his barrier also inflicted high elemental damage to your entire party. Fortunately, if you didn't have magic that matched his barrier, you could force him to change it (at the cost of getting hit by the aforementioned damage) with physical attacks. He also had four barriers he could apply, and the most you can possibly counter are three with any given party; only ''two'' if you picked Marle as your optional teammate. The hard part of the fight actually came ''after'' he dropped his barriers entirely, because that was when he broke out his most devastating spell, Dark Matter.
** There is also a lesser example in the Jesters in his castle. It starts with a magic-blocking barrier. Use physical attacks and it barrier swaps to a physical barrier. There's also the Golems, who attack-swap based on the attacks you use on them. Of course, by simply rotating elemental attacks, you can stick them in an endless loop where they have to charge each new element. You can also wear equipment that nullifies or absorbs a certain element, then just attack with that element.
* [[OurMermaidsAreDifferent Mermaid]], a guardian of Treasure Tower in ''VideoGame/{{Dubloon}}'' does this. Sometimes she can change the weakness ''twice in a row'', [[TheComputerIsACheatingBastard and sometimes right before you attack]].
* ''Franchise/TheElderScrolls'':
** Gnarls in ''[[VideoGame/TheElderScrollsIVOblivion Oblivion]]'''s Shivering Isles expansion are a non-boss example; when hit with an elemental attack, they grow in size and strength and gain a resistance to the element of the spell, but grow weaker to other elements, requiring mages to constantly swap between spells to exploit their weakness.
** In ''[[VideoGame/TheElderScrollsVSkyrim Skyrim]]'', the boss of the College of Winterhold quest 'Under Saarthal', Jyrik Gauldurson, has an elemental shield that rotates periodically between resistance to [[FireIceLightning fire, ice, and lightning]].
* ''Franchise/FinalFantasy'' has a LOT of these:
** Perhaps the TropeMaker, ''VideoGame/FinalFantasyIII'' has a boss named Hein that does this. He's encountered just after you acquire the second set of jobs, which conveniently has a class that can [[EnemyScan scan for weakness]].
** Rubicante from ''VideoGame/FinalFantasyIV'' changes his weakness from ice to fire when he draws his cloak. Yes, this means you can kill the Fiend of Fire entirely with fire damage.
** In the DS remake of ''VideoGame/FinalFantasyIV'', Golbez has this kind of move. And uses it ''constantly''.
** ''VideoGame/FinalFantasyIVTheAfterYears'' has the Blade Dragon, the BonusBoss in [[BonusDungeon Palom's Challenge Dungeon]]. It counters with a powerful attack and heals itself if you try to use anything on it that isn't an elemental attack (such as a physical attack, Bio, or even [[EnemyScan Libra]]). [[spoiler:To win, you must use the one elemental spell type it isn't using.]]
** Several bosses in ''VideoGame/FinalFantasyV'' change their elements, the most infamous being Archeoaevis and BonusBoss Omega MK II.
** ''VideoGame/FinalFantasyVI'' has Number 024, Master Pug/Tonberry, and the [[BonusBoss Magi Master]]; the latter is especially frustrating for being fought in a dungeon where only magic can be used. The UpdatedRerelease includes [[ThatOneBoss Kaiser Dragon]] as well. Luckily for you, except for Magi Master, all the other ones will change their attack pattern depending on what their weakness is. Also, you can use the Debilitator to add another weakness to them... until they barrier change again, anyways.
** ''VideoGame/FinalFantasyVII'' has Jersey, found in Shinra Mansion in Nibelheim. It is an enemy which determines if it is immune to magic or physical damage by raising one arm and lowering the other arm.
*** A unique example in the form of Lost Number, a BonusBoss in the Shinra Mansion. It starts the battle using powerful but not devastating physical and magical attacks. After losing half its HP, it will change to reflect the source of the most damage it received: if most of the damage was done with magic, it will become immune to magic and use extremely powerful magic attacks exclusively. A similar effect occurs for physical attacks, which tend to be ''slightly'' less devastating as it can still only hit one character at a time.
** Spherimorph and Greater Sphere in ''VideoGame/FinalFantasyX''. While the former's weakness can be revealed by attacking it, Greater Sphere loves to counter any action against it with Ultima. [[spoiler:Seymour Omnis]] changes elements as well.
** Some high-end bosses in ''VideoGame/FinalFantasyXI'' have the ability to either negate physical or magical damage, one of the more notable ones being the FinalBoss of ''Chains of Promathia''. There are also a few [[DemonicSpiders normal enemies]] that have such abilities, too.
** Shemhazzai from ''VideoGame/FinalFantasyXII'' has this, though this isn't present when she joins you.
*** Most bosses past about the halfway point, and virtually all [[BonusBoss Bonus Bosses]] have alternating Palings, barriers which make them immune to either magic or physical damage.
** Amphisbaena in ''VideoGame/FinalFantasyXIII''. Although the "Barrier Change" is easier to deal it because characters can use multiple spells at once, the [[NintendoHard "Boss"]] part is a little harder to manage. They come back as DemonicSpiders later in the story.
*** [[spoiler:Cid Raines]] will adapt his fighting style and the abilities used based on your paradigms.
*** The Aster Protoflorian, whose first appearance (that's right, ''even'' stronger versions appear later as DemonicSpiders) is specifically meant to [[ThatOneBoss give you a wake up call]] if you've still not got the battle system sussed. It periodically switches its attacking element, making the opposing element its weakness. Hopefully, you've been grinding enough to have a spell of each element unlocked...
* The FinalBoss of ''VideoGame/FreedomForce vs. the 3rd Reich'', which leads to the possibility of [[RealityWarper turning the most powerful being on Earth]] [[WeaksauceWeakness into a vase]] [[ItMakesSenseinContext of flowers]].
* Kushidra, a minion used by the FinalBoss of ''VideoGame/JadeCocoon'', changes elements every few turns in a predicable cycle. In ''Jade Cocoon 2'', [[spoiler:Lilith does the same]].
* In ''VideoGame/JadeEmpire'', Emperor Sun Hai doesn't care about ''elements'' per say, but he does switch between his Support, Magic, Unarmed, and Weapon Styles. Unlike most of the examples on this list, he's immune to the one he's using, not the ones he isn't, but he is very reliable about switching to whatever you just hit him with, then hitting you while you're busy changing to match.
* ''VideoGame/KingdomHeartsI'' has two of these:
** Ursula shuffles her weakness, but the mechanism is different. It's actually her ''cauldron'' that has the weaknesses. The color of its contents determines its element: attacking the cauldron with its opposing element will result in it stunning Ursula.
** One of the secret bosses ([[spoiler:Phantom]]) shuffles weak points as well, including physical hits. It's also annoying because [[spoiler:Phantom]] is also a TimeLimitBoss because of a curse on the Big Ben.
** The international and final mix versions add a third boss to the list: [[spoiler:Kurt Zisa]]. Instead of changing elements, he alternates between [[AntiMagic sealing all magic attacks]] and creating an anti-physical barrier. The former is especially annoying since it also seals spells like [[ForceField Aero]] and [[HealingHands Cure]].
* The final boss of ''VideoGame/MagicalStarsign'' changes its own weakness.
* ''VideoGame/MegaManBattleNetwork 6'' has Elementman.EXE, who changes his element after every attack.
* In ''VideoGame/MegaManXCommandMission'', Incentas had the ability to rotate his element. And his head.
* The Barroth of ''VideoGame/MonsterHunter Tri'' is weak against water while covered in mud, and weak against fire when not. He flings his mud off by shaking in one of his attacks, and sometimes rolls in mud to cover himself back up. You generally just have to pick either a fire or a water element weapon and try to attack just parts that are covered/uncovered, but Bowgunners can bring both Water and Fire shots.
** Barroth also carries a secondary weakness to Ice that doesn't change with the mud armor's state, [[TakeAThirdOption allowing players to ignore the whole thing]].
** Alatreon changes weaknesses depending if he's flying or not, Ice and water on ground, Fire or Dragon while flying.
* The Barrier Trio in ''VideoGame/{{Mother 3}}'' are immune to all elemental PSI attacks except one while they're posing, and after taking three hits from the one they're weak against, they'll change their pose, and with it, their weakness. This is one of the few instances where Boney's [[EnemyScan Sniff]] command is very useful, though it's not actually necessary if you opt for non-elemental attacks or realize that their weakness is determined by which one of the trio is calling out the pose.
* The FinalBoss of the infamous ''Mother/Earthbound'' hack ''VideoGame/TheHalloweenHack'', [[spoiler:Dr. Andonuts]], becomes one in his second form. He starts out weak to Timestop, then, when he starts using Fire, he becomes weak to Freeze. The third phase inverts his strength and weakness, while his fourth phase can easily be taken out by reflecting his ultimate attack. His final phase is a straight out fight to see who kills who first.
* ''Franchise/{{Pokemon}}'':
** Kecleon's Color Change Ability allows it to change its type to that of the attack that was just used against it, shuffling its ElementalRockPaperScissors weakness as well. [[CurbstompBattle Extra fun]] if you have a 'mon in your party with Dragon-type moves, as Dragon types are weak to attacks of the same type.
*** Now it gained the Hidden Ability Protean, which changes its type to whatever move it's going to use, basically giving it STAB on ''everything''. The Froakie line also has this Ability as its Hidden one.
** Another Pokémon does this as well -- the Porygon family's Conversion (changes type to that of one of its own attacks) and [=Conversion2=] (changes type to what resists the last attack that hit) attacks. The latter is a bit more useful in Double Battles ([=Porygon2=] are sturdy enough that it can Recover the damage dealt by its partner. [=PorygonZ=], not so much.), though it's still not recommended.
** The move Camouflage changes the Pokémon type depending on the environment.
** There's also Castform, with its ability to change its type, as well as the effects of its signature move, Weather Ball, depending on the weather, becoming Fire-type in strong sunlight, Water-type in rain, and Ice-type in hail (though strangely, there's no alternate form for a sandstorm).
** The final boss of ''VideoGame/PokemonSuperMysteryDungeon'' does this. It starts off [[NonElemental with no type]], and changes to three other types as the fight progresses.
* ''Franchise/ShinMegamiTensei''
** In ''VideoGame/{{Persona 4}}'', [[spoiler:Namatame]]'s shadow does this. He is highly resistant (to the point of single digit damage) to all but one element, which he takes high damage from. [[spoiler:The trick is that he is weak to the element he uses to attack]]).
** In ''VideoGame/{{Persona 3}}'', this is used for [[spoiler:Nyx Avatar]], the final boss, the Emperor/Empress DualBoss, and the BonusBoss, [[spoiler:Elizabeth]], who changes her persona every turn, which also changes the type of attacks that she nulls.
** As does [[spoiler:Isamu/Noah]] in ''VideoGame/ShinMegamiTenseiIIINocturne''. What makes him ''particularly'' annoying is that he shifts barriers and ''only one element can hurt him''. Anything else will be reflected. Pretty much every BarrierChangeBoss in the SMT games can be bypassed with Almighty skills. But [[spoiler:Noah]]? He takes only 10% damage from Almighty skills, so you ''will'' have to pay atention to his pattern. That is, [[spoiler:unless you get Pierce and Freikugel on the Main Character (which means being locked into the True Demon Ending), then you can just nuke Noah with Focused Freikugels.]]
** In ''VideoGame/ShinMegamiTenseiStrangeJourney'', both the normal FinalBoss and the ultimate BonusBoss randomly change weaknesses and resistances. Thankfully, there's a cheap Sub App (Gibdo Eye) that changes your cursor's appearance when your attack won't work. Most players skip the game of "What works now?" and jump straight to Almighty spells, which cannot be resisted.
** In ''VideoGame/ShinMegamiTenseiIV'', Seraph, one of the bosses in [[spoiler:Purgatorium]], puts up a colored wall that corresponds to a certain element. Using that element will break the wall and allow Seraph to be damaged.
** ''VideoGame/ShinMegamiTenseiIVApocalypse'' has three of these. The first is [[spoiler:Inanna]], the fifth boss of [[spoiler:the Cosmic Egg]], who uses moves that makes her weak to the opposite element. The second is the same dungeon's final boss, [[spoiler:Vishnu-Flynn]], who, in his second form, switches between being weak to Light and Dark. DLC provides the third example in Cleopatra, who starts with a weakness to Dark while occasionally using a move that will switch her weakness when it is exploited.
** ''VideoGame/DigitalDevilSaga''
*** Huang Long, one of the last [[BonusBoss Bonus Bosses]] in the first game, has this gimmick and he can shift barriers as well. You're supposed to use the element that comes after whatever the boss is using (ie; Huang Long is using Fire, use Ice). Huang Long however also possesses a form where [[TheComputerIsACheatingBastard he is immune to everything, including Almighty]].
*** Abaddon and Meganada in the sequel count as well. Abaddon basically has three forms that are reminiscent of three previous bosses and thus also has their elemental properties and attacks. One form uses Physical skills, another form uses magic, and the last form buffs, debuffs, and poisons. He always starts out in the Physical form, and once he's been in all three forms, he will randomly shift them around. Abaddon also possesses a nasty trick: he can swallow a party member, leaving you with only two damage dealers. [[spoiler:Pray that this hits Cielo because he actually forces himself into the active party for this battle.]] As for Meganada, he can render himself immune to either Physical or elemental magic attacks depending on what aspect the boss is using. He starts out immune to Physical and what is common with both of these aspects is that Meganada [[HealingShiv absorbs]] [[ShockAndAwe Electricity]] and has [[ContractualBossImmunity standard boss immunities]].
*** Vishnu and Shiva, both of them being [[BonusBoss tough Bonus Bosses]] in Digital Devil Saga 2, also change barriers. Shiva can only be hit by certain elements and what hits him is consistent depending on the turn order (on the first turn, only Fire and Ice will hurt him; everything else except [[NonElemental Almighty]] will be [[AttackReflector reflected back in your face]].) Vishnu however changes his resistances based on what you used against him.
*** The last BonusBoss, [[VideoGame/ShinMegamiTenseiII Satan]], also changes resistances every turn. Put this on top of [[SequentialBoss the other type of phase change]] and the fact that he can fully heal himself towards the end of the fight, and you get [[SNKBoss one very difficult opponent]].
** ''VideoGame/DevilSurvivor2'':
*** [[spoiler:Beelzebub]] normally reflects ''everything'' and {{No Sell}}s Curse element (thankfully, he doesn't resist Almighty), but depending on what {{Mooks}} he summons, he stops reflecting one element, and the fewer the number of mooks, the more vulnerable he is to that element. Problem is, as soon as he is attacked, or once there are no mooks left, he will summon a new set of mooks and change his elemental resistances.
* ''VideoGame/GoldenSun'': As part of its MoveRoulette, the Dullahan BonusBoss will occasionally use something called Element Swap. This doesn't actually affect its weaknesses, but it does serve as a warning that he's going to use an earth element move next, which includes Charon (the single most powerful Venus element SummonMagic, which only the player has normally). And while it certainly counts as ThatOneAttack, [[ThatOneBoss it's not his most aggravating one.]]
* ''VideoGame/NocturneRebirth'' gives the FinalBoss, [[spoiler:Khaos]], who has the skill Element Raid. The game lacks an EnemyScan feature, making this skill quite annoying, though the upside is that it changes his weakness and resistance in a cycle and it doesn't protect him from pure physical damage.

[[folder:Shoot 'Em Ups]]
* In ''VideoGame/{{Ikaruga}}'', the players and the second-to-final boss have the ability of switching their color. Shots of their current color are absorbed.

[[folder:Web Games]]
* ''VideoGame/EpicBattleFantasy'':
** The FinalBoss of ''3'' does this. It takes him a ''long'' time to change, though, and once he's been scanned once, you don't need to scan him again.
** ''4'' does this with the Crystal Golem, the ''second'' boss of the game, who changes between FireIceLightning ''as soon as it takes a single hit'' (that includes individual hits from multi-hit attacks). Like the above, once it's scanned you don't have to do it again.
*** However, you can [[CuttingTheKnot bypass this by attacking with the Water and Bomb elements]], although they won't be quite as strong.
* ''VideoGame/{{MARDEK}}'' has the BonusBoss [[NamesToRunAwayFromReallyFast Annihilator:Karnos]], which occasionally switches to a random new element. [[PowerCopying Legion's]] Gemsplosion attack will ''always'' trigger this.
** The [[SiliconBasedLife Master Stone]] switches elements ''every turn'', in addition to its normal attacks. The best way to deal with the Stone is to [[AntiMagic curse]] it, which not only locks it in its current form but also limits it to a relatively weak physical attack.
* The Magneto [[BonusBoss Epic Boss fight]] in Chapter 4.4 of ''VideoGame/MarvelAvengersAlliance'' makes your ability to get past his barrier a matter of sheer luck. At the start of each round, he activates either a positively or negatively charged shield, then uses attacks that place either a positive or negative charge on your party members. Damage from negatively charged characters will be absorbed by a negative shield but bypass a positive one, and vice versa. It's sometimes possible to break the shield by hitting it with enough firepower, but Magneto always puts up a fresh one each round. If the RandomNumberGod refuses to cooperate by putting any opposing charges on your team, your best bet is to either pile StandardStatusEffects on Magneto or use items to wear him down.

!!Non Video Game Examples

[[folder:Anime and Manga]]
* While Arceus always had the ability to change its types and by extension its resistances and weaknesses in the Pokémon franchise, it was never able to do this while battling. In the movie ''Anime/PokemonArceusAndTheJewelOfLife'' however, this trope is played straight. Arceus can change its plates to achieve immunity or at least heavy resistance to almost all attacks.
* In the Literature/{{Discworld}} novel "Discworld/{{Hogfather}}" a crucial door is magically locked with 8 different locks. Each one is a different color, and requires a very different technique to open. Although Mr. Teatime does not know how, he temporarily hires a wizard who figures it out.

[[folder:Live-Action TV]]
* ''Series/StarTrekTheNextGeneration'' features the Borg, who are able to adapt their personal energy shields after a couple of phaser blasts to gain effective immunity to enemy weapons. Eventually the crew of the U.S.S. Enterprise figured out that they should [[spoiler:modify their phasers to randomly switch frequencies after each shot to keep the Borg off their game.]] Even then, they adapt after several shots.

* In Creator/SternPinball's ''[[Pinball/StarTrekStern Star Trek]]'', the requirements for "Vengeance Multiball" changes depending on which encounter it is. For example, the first time is a standard multiball mode, while the second time is a TimedMission where the ''Vengeance'' shoots pinballs at the player.

* ''TabletopGame/DungeonsAndDragons'':
** The skindancer reflexively changes resistances to take less damage from whatever attack form was used on him last.
** The Initiate of the Sevenfold Veil prestige class essentially allows a PC to become one of these herself, (eventually) creating any of seven different barriers, each with a different effect on objects and creatures that pass through it (ranging from stopping missile attacks to [[WeaponizedTeleportation warping creatures to a random plane if they fail a Will save]]), and each dispelled by contact with a different spell. (They're even color-coded in the sourcebook, though the text encourages players to invent their own flavors for RP purposes.)