Polymorph

Polymorph refers to the magic that changes one creature into a different species, or changes an object to another object of the same type. A polymorph that affects you or a monster does not polymorph items carried in your or its inventory, although see below for effects on armor. Shapeshifters have a similar but slightly different power.

Several things can polymorph you, monsters, or objects:
 * ring of polymorph will polymorph you from time to time
 * spellbook of polymorph will polymorph you, monsters, or objects
 * wand of polymorph will polymorph you, monsters, or objects. Hostile monsters zap it at themselves, but never use it against you or your pets. Zapping a wand of polymorph, or casting a spell of polymorph, at yourself or a monster will not affect your or the monster's inventory.
 * polymorph trap will polymorph you or monsters. Hostile monsters deliberately step into it once. Magic resistance protects against it.
 * potion of polymorph will polymorph you (if you quaff it), a monster (if you throw it at a monster; this also angers a peaceful monster), or an object (if you dip an object into the potion of polymorph).
 * eating the corpse of a chameleon or a doppelganger will cause you to polymorph.
 * eating or being bitten by a werecreature will polymorph you from time to time into that creature's beast form. This can be cured by prayer, quaffing holy water, or eating a sprig of wolfsbane.
 * drinking toxic waste from a sink

→ Polypiling is the practice of aiming polymorph at a pile of junk, hoping to produce better or rare items.

→ Polymerge combines stacks of items into golems.

When a creature is wearing 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. When this happens to a monster, a distinctive sound results, which may warn you that a polymorph trap is present on the level. When a creature becomes too small for its armor, the armor falls to the floor, also creating a distinctive noise. An exception is when you are wearing a dragon scales or mail (such as silver dragon scale mail) and get polymorphed into a dragon (in this case, a silver dragon) where your armor will "merge" with the dragon and not be destroyed, though the cloak and shirt will still be.

Self-polymorph
Self-polymorph is always temporary, unless you wearing an amulet of unchanging; you will eventually return to your old form. The polymorph will time out. If your HP reaches zero while polymorphed, you will also return to your old form instead of dying. Being polymorphed will only "protect" you from death caused by HP loss. Dying in any way that does not reduce your HP, such as stoning, sliming, sickness, and the touch of death will kill you, rather than revert you to your original form. If you still have hands, a quick way out of an undesirable morph is to throw (non-weapon) objects up < until you "die".

If you have polymorph control, from wearing a ring of polymorph control or having eaten one and absorbed its intrinsic, you get to choose which monster to become.

If you are wearing dragon scales or dragon scale mail, you turn into that color dragon instead of a random monster, although wearing gray dragon scale mail will prevent a polymorph trap from affecting you by conferring magic resistance.

Unchanging (from an amulet of unchanging) completely prevents all polymorphs. If you are polymorphed already, it prevents you from returning to your old form.

Polymorphs caused by a polymorph trap have a (19-Con)/20 chance of causing a system shock, which results in d30 damage and exercise your constitution. You might also polymorph to your own race and die of level drain if applicable, see below.

If you genocide your base species while polymorphed, you will "feel dead inside". If you subsequently return to that form, you will die, even if you are wearing an amulet of life saving. If you quit before you return to your base form, the death message will be "quit while already on Charon's boat".

There are various strategic uses of self-polymorph. One can become a monster with higher base speed, a monster immune to stoning, a monster able to eat amulets and/or rings in order to absorb intrinsics, or a monster with a useful monster power. Monster powers include a were-creature's ability to summon pets, laying eggs which hatch into pets (only if the polyform is female), a spider's able to spin webs, and many others. Disadvantages to polyself include losing the use of one's hands, losing the ability to wear armor, and losing encumbrance capacity.

One use of the self-polymorph would be turn yourself into a dragon, especially early on. Laying an egg in order to get a baby silver or gray dragon as a pet can help you to defeat otherwise difficult monsters for higher levels. If you lay several eggs, grow all the baby dragons into adult, and get them killed (for an early character the best method is either conflict or untaming some of them and having the tame dragons defeat the untamed ones) then you have a good chance of getting dragon scales for creating dragon scale mail.

If you are self-polymorphed into a brown pudding and split, the clones will remain after you return to your normal form, and their names will be the same as your name.

Attributes, intrinsics, and other stats
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 black dragon, your strength will be 18/**. If you eat a 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.

If polymorphed to a strong monster (i. e. a dragon), your strength becomes 18/** until you return to an old form.

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

Hunger is not affected by polymorph or returning back. Even if you polymorph to a non-eating creature when fainting, you will continue to faint without a way to satiate your hunger.

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 from human to human etc.
Polymorphing to your own race is a special case. Instead of being temporary polymorphed to a monster, you see the message "You feel like a new (man, woman, elf etc.)" and your parameters are randomly 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 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 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 10% chance to change_sex.
 * Your strength, dexterity, constitution and charisma change by -2 to 2 points (attrib.c).
 * It sets your hunger to a random value from 0 to 999.
 * It cures both sickness and food poisoning (by calling potion.c with SICK_ALL).
 * 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 new current or maximal hp is 0 or negative, but you have polymorph control, they become 1 instead.
 * If your new current or maximal hp is 0 or negative, and no polymorph control, you die but can be saved by amulet of live saving.

There is nothing in this part of the source code to cure blindness (is this correct?) or to remove intrinsics that you gained from outside (for example by eating the corpse of a floating eye).

This process has curing effects, but for healthy adventurers, the DevTeam seems to have intentionally designed this function such 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, the luck integer has no effect here. You also cannot use a unicorn horn or other such cure to regain any lost levels or attributes. The comment at line 144 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.

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 man" like in a previous section.

Polymorphing to a monster while being another or the same monster is equivalent to returning to your human form and immediately polymorphing to the target monster. If you polymorph to a monster while being the same monster, you see the message "you feel like a new (monster)".

Monster versus adventurer polymorphs
NetHack treats the situation differently depending on whether you (as the adventurer) or a monster polymorphs.

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

An interesting case of this is lycanthropy. If you have this condition, you will sometimes polymorph into a canine (a jackal, for example). There is also a monster in the game called a werejackal, which in its human form will also sometimes become a jackal. As the jackal, either you or the monster can summon allied jackals as help. (If you summon them, then you keep the jackals as pets.) The similarity ends when as the jackal, you or the monster lose all of your health. You will become your normal race again, while the monster will die without transforming back into a human.

SLASH'EM changes the behavior from vanilla NetHack. In SLASH'EM, monster polymorphs behave more like player polymorphs in that monsters who are killed while polymorphed will revert to their original form. Polymorphed items will also return to their original forms after a certain amount of time.

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, 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. , ) are permitted, as are the functionally-human s.  You may also polymorph into your own race, as above.
 * anything represented by human or elf, except the Elven variants mentioned above
 * the greater angelic beings: s,, and s.  and  are permitted.
 * "limited-edition" monsters: and
 * s and s
 * natural shapeshifters: s, s, and s
 * s, s,, and s

SLASH'EM
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.

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, you will not be able to permanently upgrade your pet with polymorph.

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.

SLASH'EM features a new monster, the genetic engineer, whose attack polymorphs you.

When a player polymorphs into a xorn in SLASH'EM, then returns to his or her original form, the player will be stuck in a pit that disappears after scrambling out. Presumably this is to simulate the xorn's partial immersion in the surrounding earth.