Polymorph refers to the magic that changes one creature into a different species, or changes an object to another object of the same type. Shapeshifters 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 a different article.
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 pets can be changed into powerful ones. You can also polymorph surplus items into more useful equipment.
A wand or spell of polymorph can be aimed at oneself ., or at monsters or piles of items on the floor. Aiming downwards > polymorphs the objects on your square; aiming upwards has no effect. Dipping 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 be eaten for a 1/3 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).
- 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 digesting a sandestin.
- Becoming afflicted with lycanthropy, and thus polymorphing into a werecreature from time to time.
- In SLASH'EM, getting hit by a genetic engineer.
- In SLASH'EM, using the #youpoly extended command for races and roles that have that ability.
The inventory of a polymorphed monster is not polymorphed. However, worn armor can be destroyed or temporarily absorbed. Magic resistance blocks the effect of all "involuntary" polymorphs. A monster's MR will protect it against polymorph traps, but magic cancellation will not protect you.
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 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, either by you or a monster; these include:
- any monsters that have been genocided. This will result in the message "You feel rather <monster>-ish."
- all unique monsters.
- the base player race monsters (@ human, h dwarf, @ elf, G gnome, o 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. h dwarf lord, @ Elvenking) are permitted, as are the functionally-human K Keystone Kops. You may also polymorph into your own race.
- any creature represented by @, except the Elven variants mentioned above.
- the greater angelic beings: A Angels, A ki-rin, and A Archons. The lesser angels A Couatl and A Aleax are permitted.
- "limited-edition" monsters: W Nazgul and & erinys.
- ghosts and shades.
- natural shapeshifters: @ doppelgangers, : chameleons, and & sandestins.
- & water demons, & mail daemons, & djinni, and ; krakens.
If you polymorph without polymorph control and it is not a special case, there is a (19-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 1/25 after factoring in resistance. If the monster is affected, it will die instantly and not leave a corpse.
- "You break out of your armor!"
- "You hear a ripping sound."
- See also: physical size
When a creature is wearing torso armor (body armor, a shirt and/or a 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, a distinctive sound results, 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.
- "Your armor falls around you!"
- "You hear a clank. You hear a thud."
When a creature becomes too small for its armor, the armor falls to the floor, also creating a distinctive noise. Monsters of size Small will shrink out of torso armor; Tiny monsters also shrink out of boots, gloves and helmets (they can wear no armor). Non-humanoid monsters, or monsters without suitable body parts, also cannot wear certain types of armor.
If you were wielding an object and your new form has no hands, you will drop it.
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 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.
- Note that SLASH'EM makes monster polymorph temporary; see the #SLASH'EM section.
Shapeshifters and werecreatures have innate polymorph ability and will change to a different form from time to time. (You can prevent them 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 fleeing, it may use a potion or wand of polymorph, or an adjacent polymorph trap in a desperate move: "The <monster> deliberately jumps onto a polymorph trap! / The <monster> quaffs a <potion appearance>! / The <monster> zaps <itself> with a <wand appearance>!" 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.
An example of the difference is with lycanthropy. If you have this condition, you will sometimes polymorph into a creature (a jackal, for example). There is also a monster in the game called a werejackal, which changes from its 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.
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 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.
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. If you have many charges in a wand of polymorph, or are able to cast the 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.
Note that 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 eating corpses. If it acquires a high level and monster MR, it may also become immune. Otherwise, you can keep trying. See preferred pets for pets that other players find useful.
You can also gain new pets by creative ways of polymorphing yourself. These new pets can then be turned into more powerful ones as above. See the #Strategy section.
Having polymorph control allows you to specify what to polymorph yourself into, unless you are unconscious or stunned. This is subject to the game restrictions. For strategy, see Polymorph control#Strategy.
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 and effects on armor.
- If you are already polymorphed into a vampire, you turn into a vampire bat.
- If you have lycanthropy, you turn into the corresponding werecreature.
- You may also suffer system shock and not polymorph.
- Otherwise, you turn into a random creature (or your own race, 1/5 probability).
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. See Dragon_scale_mail#Polymorph for more information.
Polymorphing yourself is never permanent, unless you polymorph into your own race (see "Polymorphing into your own race", below). Otherwise, you will stay in monster form for 499+1d500 turns. If your new monster form has a higher experience level than you, the timeout is scaled down in proportion to the levels. If the timeout ends but you are wearing an amulet of unchanging, 1d(1+100*mlevel) turns are added to the timeout. mlevel refers to the 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 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, hunger or a touch of death, you will immediately die. Due to the internal workings of NetHack, being beheaded by Vorpal Blade or bisected by the Tsurugi of Muramasa are also considered deaths by HP loss, and return you to original form.
If you are polymorphed into a weak form, you can zap a wand at yourself or throw an object upwards < so that it hits you, causing you to lose HP and change back. If you have no hands, a prayer to your god may change you back as well. Lack of hands should make you incapable of throwing items, but as result of bug C343-243 this is not a problem in vanilla NetHack and variants without fix for this bug. 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.
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 death message will be "quit while already on Charon's boat".
Attributes, intrinsics, and other stats
Your new HP is determined by the monster form's base level. This level is displayed instead of your experience level in the status bar, eg. HD: 13 for a master mind flayer. Your "real" level can be determined from spell failure rates (e.g. for the quest). Any change in current or maximum HP is temporary. Your Pw persists between forms.
Five of your six attributes (Strength, Dexterity, Constitution, Intelligence, and Charisma) 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. Wisdom is the only attribute which persists between forms.
Things are different with intrinsics. As a monster you will enjoy all intrinsics which you had before your polymorphed, all intrinsics of your new species, and all intrinsics 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 polymorph or returning back, only by polymorphing into your own race.
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.
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 -2 to 2 levels.
- 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, and no further changes applied.
- If the new level is lower than the old one, it cannot be cured by a blessed potion of full healing.
- Your innate properties, resistances, and #enhance weapon slots are adjusted to match your new level.
- It grows or shrinks your maximal HP (over the first 10 points) and energy, in proportion to your level change, then applies a further adjustment of -9 to 9 points.
- If your new maximal energy is negative, it becomes 0.
- Your current HP and energy are adjusted proportionally to the change of maximal HP and energy.
- You have a 1/10 chance of changing sex.
- Your strength, dexterity, constitution and charisma change by -2 to 2 points (attrib.c).
- It sets your hunger to a random value from 500 to 999.
- It cures both illness and food poisoning.
- It cures stoning, if you had been stiffening.
- It would cure sliming, but slime remains on your body, thus the sliming process restarts and you have 10 turns to live. (The DevTeam Thinks Of Everything.)
- If your current or maximal HP is now 0 or negative, but you have polymorph control, they become 1 instead.
- If your current, or maximal HP is now 0 or negative, and no polymorph control, you die but can be saved by an amulet of life saving. In case of saving:
- If your maximal HP is 0 or negative, it increases to 10.
- You current HP increases to your maximal HP.
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 xanthian explains to rgrn, the expected value of the level change is zero. Because this function does not call rnl, your luck has no effect here. You also cannot use a unicorn horn or other such cure to regain any lost levels or attributes. A comment explains how the source code adjusts your peak level to prevent this. The redist_attr function sets both your current and peak attributes, too. The becoming of a new man (or new gnome) many times is no way to raise your experience level or your attributes.
It is still 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 can accumulate the effects of gaining levels, which multiplies hit points and power. This is 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>!"
Polymorph in SLASH'EM functions in a considerably different way than in vanilla NetHack. In SLASH'EM, all polymorph operations are temporary; this includes the polymorphing of monsters into other monsters and the polymorphing of objects. Polymorphed items revert back to their original form after 500–999 turns  and polymorphed non-player monsters revert back to their original form after 1000–1999 turns . For monsters, the change can only be made permanent by stoning and unstoning the polymorphed monster. Items can be "fixed" in their current form by dipping them in a potion of restore ability.
When a monster that has been polymorphed into another monster (by wand, spell, trap, etc.) is destroyed, it reverts to its original form with reduced HP. Thus, it is no longer possible to slay dangerous enemies such as shopkeepers with polymorph (though you may be able to disable, immobilize, or slow them enough to rob them without killing them). Note that monsters such as chameleons and lycanthropes are much harder to kill under this system because they have the option of reverting to a different form during combat. Furthermore, it is no longer a simple matter to permanently upgrade your pet with polymorph.
If you polymorph into an intelligent monster with an attack that requires direct contact (biting, tentacles, etc), you will not use this attack against petrifying monsters, as opposed to being instantly stoned. Attacking bare-handed will still stone you, however. If melee damage rehumanizes you, your monster difficulty can be subtracted from your current and maximum hit points. This always occurs if the polymorph was controlled, and 1/3 chance otherwise.
Polymorphed objects in SLASH'EM will also, eventually, revert, making polypiling of rings, wands, and equipment much less effective (and potentially dangerous--if for example you start wearing an amulet of life saving that used to be an amulet of strangulation). However, a polymorphed object in SLASH'EM can be fixed to its new form by being dipped in a potion of restore ability. Objects that vanish after a single use, such as potions and scrolls, will operate normally, and the fact that they would have reverted does not change the effect they do have. Objects which have been polymorphed and will eventually revert are not marked as such in a normal game, but in wizard mode will appear with the description "hazy", e.g. "a hazy key."
SLASH'EM features a new monster, the genetic engineer, whose attack polymorphs you.
- mondata.h in NetHack 3.4.3, line 77: See also monst.c, which lists the monsters to which this applies.
- polyself.c in NetHack 3.6.1, line 839
- Source:NetHack_3.6.0/src/polyself.c#polyself, PROT_FROM_SHAPE_CHANGERS cannot be found in the code
- polyself.c in NetHack 3.4.3, line 396
- polyself.c in NetHack 3.4.3, line 452
- The exact condition for stoning a monster with a wielded trice 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, chromatic Dragon.
- polyself.c in NetHack 3.4.3, line 138
- polyself.c in NetHack 3.4.3, line 169
- polyself.c in NetHack 3.4.3, line 188
- polyself.c in NetHack 3.4.3, line 190: This calls make_sick in potion.c with SICK_ALL
- polyself.c in NetHack 3.4.3, line 210
- polyself.c in NetHack 3.4.3, line 144
- timeout.c in SLASH'EM 0.0.7E7F2, line 455
- timeout.c in SLASH'EM 0.0.7E7F2, line 590
- mhitu.c in SLASH'EM 0.0.7E7F2, line 2555