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In ''[[NetHack]]'', '''polymorph''' refers to the [[magic]] that changes one creature into a different species, or changes an [[object]] to another object of the same type. [[Shapeshifter]]s and [[werecreatures]] have similar, but slightly different abilities.

This article deals mainly with monster- or self-polymorph. The practice of polymorphing objects is also known as '''[[polypiling]]''', and is explained in the article behind that link.

Polymorph is one of the more complex aspects of ''NetHack''. It can be a great danger if not done under the control of the player, but a prepared player can use it to gain many benefits. If you are transformed unexpectedly, you may turn into a weaker monster or die instantly; your valuable [[armor]] may also be destroyed. A weak enemy may unexpectedly turn into a dangerous one. On the other hand, you can deliberately turn into a much stronger monster, or a monster with useful abilities. Weak [[pet]]s can be changed into powerful ones. You can also polymorph surplus items into more useful equipment.

== Polymorphing ==
A [[wand of polymorph]] or {{+ of|polymorph}} spell can be aimed at monsters or piles of items on the floor. Aiming downwards using {{kbd|>}} polymorphs the objects on your square; aiming upwards using {{kbd|<}} has no effect; and aiming at [[you]]rself using {{kbd|.}} will naturally polymorph you. [[Dip]]ping an object into a [[potion of polymorph]] will polymorph it.

Other sources of polymorph do not apply to objects:
* Wearing a [[ring of polymorph]] will polymorph you from time to time. It can [[eating jewelry|be eaten]] for a {{frac|3}} chance of acquiring the intrinsic.
* Stepping into a [[polymorph trap]] will polymorph you or a monster. The trap disappears after you use it once, but monsters can use it indefinitely.
* Quaffing a [[potion of polymorph]] will polymorph you or a monster.
** Getting hit by this potion. Thankfully, monsters will not do this to you; only you can do this to them. [[Vapors]] will not polymorph you (good for use-testing).
* [[Sink#Quaffing from a sink|Quaffing from a sink]] produces toxic wastes, or randomly dispenses potion of polymorph; both effects will polymorph you.
* Eating the corpse of a [[chameleon]] or [[doppelganger]], or [[digestion|digesting]] a [[sandestin]].
* Becoming afflicted with [[lycanthropy]], and thus polymorphing into a [[werecreature]] from time to time.

The inventory of a polymorphed monster is not polymorphed, but worn armor can be destroyed or temporarily absorbed. [[Magic resistance]] blocks the effect of all "involuntary" polymorphs; this means that it will not protect from a ring of polymorph, which is considered to be worn voluntarily. A monster's [[Magic resistance (monster)|MR]] will protect it against polymorph traps.

If you polymorph into a form that is not the same as your starting race, you break the [[polyselfless]] [[conduct]]. ("Changing" into your original race is not a polymorph, strictly speaking, and this article calls it "[[#Polymorphing into your own race|Polymorphing into your own race]]".) Polymorphing any object breaks the [[polypileless]] conduct.

== Effects of polymorph ==
:''For effects specific to yourself, see [[#Self-polymorph]].''

=== Restrictions on polymorphing ===
Certain monsters are off-limits to polymorph,{{refsrc|mondata.h|77|comment=See also [[monst.c]], which lists the monsters to which this applies.}} either by you or a monster; these include:
* any monsters that have been [[genocide]]d.  This will result in the message ''"You feel rather <monster>-ish."'' (Note: Monsters which are [[extinct]], however, are still available for self-polymorph.)
* all [[unique monster]]s.
* the base player race monsters ({{monsymlink|human}}, {{monsymlink|dwarf}}, {{monsymlink|elf}}, {{monsymlink|gnome}}, {{monsymlink|orc}}), which exist to provide corpses when zombies and mummies are killed and for bones piles (dwarves and gnomes can also be generated normally, however these are still not permitted).   Non-human variants generated as monsters (e.g. {{monsymlink|dwarf lord}}, {{monsymlink|Elvenking}}) are permitted, as are the functionally-human {{monsymlink|Keystone Kop}}s.  You may also polymorph into your [[#Polymorphing into your own race|own race]].
* any creature represented by [[human or elf|{{white|@}}]], except the Elven variants mentioned above.
* the greater angelic beings: {{monsymlink|Angel}}s, {{monsymlink|ki-rin}}, and {{monsymlink|Archon}}s.  The lesser angels {{monsymlink|Couatl}} and {{monsymlink|Aleax}} are permitted.
* "limited-edition" monsters: {{monsymlink|Nazgul}} and {{monsymlink|erinys}}.
* {{monsymlink|ghost}}s and {{monsymlink|shade}}s.
* natural shapeshifters: {{monsymlink|doppelganger}}s, {{monsymlink|chameleon}}s, and {{monsymlink|sandestin}}s.
* {{monsymlink|water demon}}s, {{monsymlink|mail daemon}}s, {{monsymlink|djinni}}, and {{monsymlink|kraken}}s.

=== System shock ===
If you polymorph without polymorph control and it is not a [[#Polymorphing into other monsters|special case]], there is a {{sfrac|19 &minus; [[constitution|Con]]|20}} chance that it will fail, and you will instead suffer 1d30 damage and abuse constitution: "You shudder for a moment." This is called [[system shock]]. Monsters and pets can also be affected by the wand, potion, or spell of polymorph, with a fixed chance of {{frac|25}} after factoring in resistance. If the monster is affected, it will die instantly and not leave a corpse.

=== Armor ===
:''See also: [[Physical size]]''

When a creature is wearing any torso armor ([[body armor]], [[shirt]], or [[cloak]]), and becomes something Large or bigger, a non-[[humanoid]] Medium or bigger, or a [[winged gargoyle]] or [[marilith]] (wings and extra arms don't fit), the armor will burst apart. (If you polymorph into a large [[whirly]] monster, the armor is not destroyed.) When this happens to a [[monster]], you hear a "ripping" or "cracking" sound, which warns you that a [[polymorph trap]] or shapeshifter may be present on the level.

If you are wearing [[dragon scales]] or [[dragon scale mail]] and are polymorphed without polymorph control, you will turn into a [[dragon]] of the appropriate color and merge with your scales; shirts and cloaks are still destroyed. See [[dragon scale mail#Polymorph|Dragon scale mail § Polymorph]].

When a creature becomes too small for its armor, the armor falls to the floor, also creating a distinctive noise ("a clank" or "a thud"). Monsters of size Small will shrink out of torso armor; Tiny monsters also shrink out of [[boots]], [[gloves]], [[shield]]s and [[helm]]s (they can wear no armor). [[Body parts|Handless]] monsters will drop gloves and shields. [[Body parts|Horned]] monsters will drop helmets. Non-[[humanoid]] monsters, or monsters without suitable body parts, also cannot wear certain types of armor.

=== Other equipment ===
Monsters can always wear [[rings]] and [[amulets]], although some may be physically unable to remove equipped items or put on additional ones in their new form.

If you were wielding an object and your new form has no [[hands]], you will drop it.

Polymorphing causes you to retouch all your inventory items,{{refsrc|polyself.c|839|nethack=3.6.1}} potentially causing [[artifact blast]]s or [[silver damage]].

=== Encumbrance ===
{{main|Encumbrance}}
Smaller or more light-weight monsters cannot carry as much as larger ones. Non-[[humanoid]] monsters have especially limited capacity. When you are unexpectedly polymorphed into one, you may have to drop nearly all of your items before you can do anything useful.

Your [[monster carrying capacity|carrying capacity]] is scaled by your form's corpse weight (or size if it leaves no corpse), and is affected by the monster "strong" attribute. See that article for the details.

== Monsters ==

[[Shapeshifter]]s and [[werecreatures]] have innate polymorph ability and will change to a different form from time to time. You can prevent them from doing this by wearing a [[ring of protection from shape changers]]. Other than that, a polymorphed monster or object stays in its new form permanently.

If a monster is [[flee]]ing, it may use a potion or wand of polymorph, or an adjacent polymorph trap in a desperate move. A monster may also inadvertently step onto the trap. If it becomes a much more powerful monster, such as an [[arch-lich]], this can lead to [[YAAD]].

When a monster polymorphs, the change is permanent. For example, if you change your [[dog]] into a [[dragon]], it will never become a dog again (except by chance in a subsequent polymorph).

If you have [[lycanthropy]], you will sometimes polymorph into a creature (a [[jackal]], for example). There is also a monster in the game called a [[werejackal]], which changes occasionally from its [[human (monster attribute)|human]] form into a jackal. The similarity ends when you or the monster lose all HP in jackal form. You will become your normal race again, while the werejackal will die without transforming back into a human.

=== Polymorphing monsters ===
Since polymorphing a monster has unpredictable results, this tactic is only feasible for very powerful monsters, as they have a good chance of becoming a weaker one. Monsters with high [[experience level]] and [[magic resistance (monster)|monster MR]] may resist polymorphing, so this is not a reliable method to escape impending death. For example, the [[Riders]] cannot be polymorphed at level 30. An [[arch-lich]] at level 25 will resist 85% of the time if you are level 30 and attempt to polymorph it with a spell; it can never be polymorphed with a wand.

Lawful and neutral characters may wish to polymorph humans such as [[shopkeeper]]s and [[aligned priest]]s before killing them, to avoid the penalties for [[murder]].

=== Pets ===
Your starting [[pet]] will only go so far: [[cat]]s and [[dog]]s reach a normal maximum of level 9 and 72 HP, for example. But you can get more out of it by polymorphing it.

Since you cannot control the outcome of a pet's polymorph, the best way to do this is to use a [[polymorph trap]] repeatedly until you get a satisfactory result. The trap is never used up by pets and other monsters. If you have [[magic resistance]], you can step onto the trap and then [[displace]] your pet onto it. You can also step next to the trap and use a [[magic whistle]] until your pet happens to land on the trap. You can also [[leash]] your pet and stand next to the trap; it does not want to step onto the trap, but it eventually will. You can also [[read]] a [[scroll of earth]], push the boulders around the trap, and then displace your pet onto the trap. If you have many charges in a [[wand of polymorph]], or are able to cast the [[spellbook of polymorph|spell]], those are viable alternatives (but beware of system shock, as it will count as you having killed the pet!) Less workable methods are finding [[chameleon]] or [[doppelganger]] corpses for it to eat, or breaking a [[potion of polymorph]] on its body.

Displacing your pet onto a trap decreases its [[tameness]] by one point. Be wary about displacing pets that have already become somewhat powerful monsters. Pets, like other monsters, can suffer a [[system shock]] if you are using the spell, wand, or potion. If the pet experiences a system shock, you will suffer the usual penalties for killing your pet.

Once your pet turns into a [[gray dragon]] or its baby form, it acquires intrinsic magic resistance and will be immune to all forms of polymorph, except from [[Shapeshifter|eating corpses]]. If it acquires a high level and [[magic resistance (monster)|monster MR]], such as if it turns into an [[arch-lich]], it may also become immune. If you do not have a magic whistle or magic resistance to displace your pet, then [[sessile]] pets will not polymorph any further. Finally, if you get a [[shapeshifter]] and do not have a ring of protection from shape changers, then it will only shapeshift on the trap. Otherwise, you can keep trying. See [[Pet#Preferred pets|Pet § Preferred pets]] for pets that many players find useful.

You can also gain new pets by polymorphing into an [[oviparous]] creature and laying [[egg]]s.

== Self-polymorph ==

Having [[polymorph control]] allows you to specify what to polymorph yourself into, unless you are unconscious or stunned.  This is subject to the [[#Restrictions on polymorphing|game restrictions]]. For strategy, see [[Polymorph control#Strategy|Polymorph control § Strategy]].

An [[amulet of unchanging]] blocks polymorph completely, but a ring of protection from shape changers will not. If you are in the form of a [[metallivore]] and can [[Eating jewelry|eat amulets]], eating one may also return you to your original form.

=== Polymorphing into other monsters ===
There are a few special cases when polymorphing in an uncontrolled manner:
* If you are wearing [[dragon scales]] or a [[dragon scale mail]] while randomly polymorphed, you turn into a [[dragon]] of the same color.  See [[Dragon scale mail#Polymorph|Dragon scale mail § Polymorph]] and [[#Armor|effects on armor]].
* If you are already polymorphed into a [[vampire]], you turn into a [[vampire bat]], a [[fog cloud]], or a [[wolf]].{{refsrc|polyself.c|530|version=NetHack 3.6.1}}
* If you have [[lycanthropy]], you turn into the corresponding [[werecreature]].
* You may also suffer [[#System shock|system shock]] and not polymorph.
* Otherwise, you have a {{frac|5}} chance of [[#Polymorphing into your own race|turning into your own race]].
* Otherwise, you turn into a random creature.

If, while wearing [[dragon scales]] or a [[dragon scale mail]], you are polymorphed into a dragon of the same color, the dragon scales will be merged into your skin.

=== Changing back ===
Polymorphing yourself is never permanent, unless you polymorph into your own race (see {{sa|Polymorphing into your own race|sectionsign=1}}). Otherwise, you will stay in monster form for 499+1d500 turns.{{refsrc|polyself.c|396}} If your new monster form has a higher [[experience level]] than you, the timeout is scaled down in proportion to the levels.{{refsrc|polyself.c|452}}. To be precise, the polymorph duration will be multiplied by 

<math>\frac {player XL} {monster XL}</math>.

E.g., if a XL 2 player polymorphs into a master mind flayer (XL 13), the duration will be at most 153 turns:

<math>999 * \frac {2}{13}</math>

If the timeout ends but you are wearing an [[amulet of unchanging]], between 1 and (1&nbsp;+ 100&nbsp;&times; <var>mlevel</var>) turns are added to the timeout. <var>mlevel</var> refers to the [[monster level|monster form's experience level]]. Eating a mimic or stepping on a polytrap while magic resistant or unchanging have no effect on the timeout.

If you are killed in your new form because your [[hit points|HP]] became zero, you will change back: "You return to <race> form!" You will return to your original form with the HP and Pw you had before you polymorphed. However, if you are wearing an [[amulet of unchanging]] or are killed in any other way, such as [[stoning]], [[sickness]], [[starvation|hunger]], [[nutrition#Hunger status|choking]], or a [[touch of death]], you will immediately die. Being beheaded by [[Vorpal Blade]] or bisected by [[the Tsurugi of Muramasa]] are considered deaths by HP loss and return you to original form.

You can return to your normal form due to HP loss even when wearing an [[amulet of life saving]], and it is not used up. However, it will protect you from [[#System shock|system shock]].

If you are polymorphed into a problematic form, you can zap a wand at yourself or throw an object upwards {{kbd|<}} so that it hits you, causing you to lose HP and change back. If you have [[trouble|no hands]], a [[prayer]] to your god may change you back as well. If a monster is attacking you and reducing your HP, these measures may be unnecessary.

Another way to change back is to polymorph into your own race.

Being a [[gray dragon]] gives you [[magic resistance]], so you cannot change back by looking for another polymorph trap.

If you [[genocide]] your original race or your role while polymorphed, "You feel dead inside." If you subsequently return to that form, you will die, even if wearing an [[amulet of life saving]]: "Unfortunately, you are still genocided..." If you [[quit]] before you return to your base form, the game-end message will be "quit while already on Charon's boat".

=== Attributes, intrinsics, and other stats ===
{{todo|Please update: confirm 1 point drop in maximum power when unpolymorphing and whether it also applies to lycanthropy.}}
Your new HP is [[HP#Monster|determined]] by the monster form's [[monster level|base level]]. This level is displayed instead of your experience level in the status bar, eg. <tt>[[hit dice|HD]]: 13</tt> for a [[master mind flayer]]. Your "real" level can be determined from [[fail|spell failure rates]] (e.g. for the quest). Any change in current or maximum HP is temporary. Your [[energy|Pw]] persists between forms.

Your [[strength]], [[dexterity]], [[constitution]], [[intelligence]], and [[charisma]] (but not [[wisdom]]) are saved when you polymorph to a monster, and restored when you get back to your old form, no matter what happened when you were polymorphed. For instance, if you had strength 16 and polymorphed to a [[dragon]], your strength will be 18/**. If you eat a poisonous [[killer bee]] corpse, your strength may be reduced to 18/97, but after returning to an old form, your strength will again be 16.

Things are different with [[intrinsic]]s. As a monster you will enjoy all intrinsics which you had before you polymorphed, all intrinsics of your new species, and all extrinsics acquired by magic items which you are wearing or wielding. You may acquire new intrinsics, and they will stay with you after returning to your old form. Therefore, if you became a dragon, it is a good idea to eat killer bees: the [[poison resistance]] which you obtain will stay with you, while the decline in your strength will not.

Hunger is not affected by polymorphing or returning back, only by polymorphing into your own race.

[[Amulet of change|Amulets of change]], if worn when polymorphed, change both your sex as your polymorphed form (if there are both male and female monsters of this kind) and your base form sex.

Players polymorphed into a [[jabberwock]], adult [[dragon]], [[raven]], or [[crocodile]] will not stone monsters with a wielded cockatrice corpse.<ref>The exact condition for stoning a monster with a wielded cockatrice corpse seems to be: (in natural form or (hit with weapon attack or hit with claw attack in slot 1 or hit with claw attack in slot 2 as a foocubus or hit with any attack in slot 1 as any L)). This also excludes the invalid polyforms Ixoth, Demogorgon, and Chromatic Dragon.</ref>

=== Polymorphing into your own race ===
Polymorphing into your own race is a special case. It does not break [[polyselfless]] conduct. Instead of being temporarily changed to a monster, you see the message "You feel like a new <race>!" and your character is randomly and permanently changed:
* It adjusts your [[experience level]] by &minus;2 to +2 levels.{{refsrc|polyself.c|138}}
** If the new level is higher than 30, it becomes 30.
** If the new level is lower than 1, you die ("Your new form doesn't seem healthy enough to survive.") If saved by an [[amulet of life saving]], you restore your old experience level.
** If the new level is lower than the old one, it cannot be cured by a blessed [[potion of full healing]].
** Your innate [[property|properties]], [[resistance]]s, and [[skill]] slots are adjusted to match your new level.
* Your [[strength]], [[dexterity]], [[constitution]], and [[charisma]] change by &minus;2 to +2 points ([[attrib.c#redist_attr|attrib.c]]).
* Your maximum [[HP]] and [[energy]] are readjusted according to your new level and [[attribute]]s in the following manner:{{refsrc|src/polyself.c|292|nethack=3.6.0}}
** First, all HP and energy gained by leveling is removed.  (The game stores these values whenever you level.)
** Then, the remainder is randomly multiplied by one of (80%, 90%, 100%, 110%), separately rolled for HP and energy.
*** The result is set equal to the new level if it ends up lower.
** Then your HP and energy are increased as if you'd leveled to your new level from 1, taking in account your current [[constitution]] and [[wisdom]] bonuses.
** Finally, your current HP and energy are adjusted proportionally to the change of maximum HP and energy.
* You have a {{frac|10}} chance of changing [[gender]].
* It sets your [[nutrition]] to a random value from 500 to 999.{{refsrc|polyself.c|188}}
* It cures both [[illness]] and [[food poisoning]].{{refsrc|polyself.c|190|comment=This calls {{function|potion.c|make_sick}} with <tt>SICK_ALL</tt>}}
* It cures [[stoning]], if you had been stiffening.
* It technically cures [[sliming]], but slime remains on your body; thus, the sliming process restarts and you have 10 turns to live.{{refsrc|polyself.c|210}}
* If your current HP is now 0 or negative, but you have polymorph control, it becomes 1 instead.
* If your current HP is now 0 or negative, and you do not have polymorph control, you die.
** If you are wearing an [[amulet of life saving]], you survive, but the checks for sliming and [[artifact blast|retouching your inventory]] are skipped.

It does not [[cure blindness]], nor does it remove any of your [[intrinsic]]s unless they were given by experience levels that you lost.

This process has curing effects, but for healthy adventurers, the DevTeam seems to have intentionally designed this function so that there is an equal chance that each adjustment is beneficial or harmful. As [http://groups.google.com/group/rec.games.roguelike.nethack/msg/ce27e3ab8608630a xanthian explains to rgrn], the expected value of the level change is zero. Because this function does not call <tt>rnl</tt>, your [[luck]] has no effect here. You also cannot use a [[unicorn horn]] or other such cure to regain any lost levels or [[attribute]]s. A comment{{refsrc|polyself.c|144}} explains how the source code adjusts your peak level to prevent this. The [[attrib.c#redist_attr|redist_attr]] function sets both your current and peak attributes, too. The becoming of a new "man" many times is thus no way to raise your [[experience level]] or your attributes.  Performing it ''once'' after maximizing your constitution and wisdom may yield a maximum HP and energy boost, though, since the level-up bonuses were likely originally obtained with lower attributes.

==== In 3.4.3 ====

Prior to [[NetHack 3.6.0]], HP and energy changed differently: they were grown or shrunk in direct proportion to your level change, then a further adjustment of &minus;9 to +9 points was applied.{{refsrc|polyself.c|169|nethack=3.4.3}}  It was consequently possible to bias the changes deliberately.  At a very low experience level, polymorph has an equal chance of raising your level, or decreasing it and killing you. By cheating death with an [[amulet of life saving]], one could accumulate the effects of gaining levels, which multiplied [[hit points]] and [[power]]. This was known as the [[polyself bug]].

===Other special cases===
Polymorphing to your own race while being a monster just returns you to your basic form and then makes you "a new <race>" as in the previous section.

Polymorphing to a monster while already being monster is equivalent to returning to your human form and immediately polymorphing to the target monster. If you polymorph to a monster while already the same species, you see the message "You feel like a new <species>!"

==Variants==
===SLASH'EM===
In [[SLASH'EM]], the attack of a [[Genetic engineer (SLASH'EM)|genetic engineer]] can polymorph the hero and other monsters, and the #[[youpoly]] [[extended command]] allows controlled polymorphing at will for races and roles with that ability. Polymorph itself functions in a considerably different manner, detailed below.

Most monster and item polymorphs are temporary: Polymorphed items revert back to their original form after 500–999 turns, and polymorphed monsters revert back to their original form after 1000–1999 turns.{{refsrc|timeout.c|455|version=SLASH'EM 0.0.7E7F2}}{{refsrc|timeout.c|590|version=SLASH'EM 0.0.7E7F2}} For monsters, temporary polymorphs can be made permanent by [[stoning]] the monster, then re-animating them with the spell of [[stone to flesh]]; eating the corpse of a chameleon or doppelganger, or digesting a sandestin, will still be permanent.

Items that are polymorphed are sometimes described as '''"hazy"''', e.g. when polymorphed using a potion of polymorph - in wizard mode, they will also appear as "hazy", e.g. "a hazy key". Polymorphed items function as the normal item would otherwise for the duration of their polymorph, and can be "fixed" permanently in their current form by dipping them in a [[potion of restore ability]]. This makes polypiling of rings, wands, and equipment much less effective and even potentially dangerous (e.g. a character wearing a hazy [[amulet of life saving]] that used to be an [[amulet of strangulation]]) unless they have several potions to spare for "fixing" items.

Killing a polymorphed monster causes them to revert to their original form with reduced HP: this makes dangerous enemies much harder to kill by polymorphing them into a weaker form, and it is also much harder to permanently upgrade a pet with polymorph. Polymorphing [[shopkeeper]]s is no longer a reliable means of killing them either, though this can still disable, immobilize, or slow them enough for a character to rob the store or else turn them to stone. Hostile shapeshifters such as chameleons and lycanthropes become especially difficult: if killed while outside of base form, they can often shapechange again before a character can deal the finishing blow - conversely, a luckier character may be able to lower their HP enough that they undergo system shock and die as normal when trying to turn back. 

When a character is polymorphed, if they become an intelligent monster with an attack that requires direct contact (biting, tentacles, etc), they will not use this attack against petrifying monsters, as opposed to using it and being instantly stoned - attacking bare-handed will still turn them to stone, however. If melee damage returns a character to normal form, they have a {{frac|3}} chance of losing current and maximum HP equal to that form's monster difficulty, and the damage always occurs if the polymorph was controlled.{{refsrc|mhitu.c|2555|version=SLASH'EM 0.0.7E7F2}}

===xNetHack===
[[xNetHack]] includes a <tt>polyinit</tt> [[option]], which allows you to play the game permanently polymorphed into any monster except for [[unique monster]]s and [[player monster]]s. Besides those, this option allows forms that are normally inaccessible, such as an [[Archon]] or [[shade]], though the game may be unstable in this state. This is a non-scoring game mode.

===SlashTHEM===
The rule chances for polymorph in SLASH'EM are still applicable in [[SlashTHEM]], though temporarily polymorphed objects will appear as "hazy" in normal play.

==References==
<references />
{{nethack-343|offset=1}}
[[Category:Spells]]