Polymorph trap

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A polymorph trap changes you to a new species, in the same manner as a polymorph spell, potion or wand. They will not be generated above dungeon level 8.[1]


You, and the trap, are not affected if you have either magic resistance or unchanging. Otherwise, the following may happen:

  • If you have polymorph control, you get to choose which monster to become.
  • If you are wearing dragon scales or dragon scale mail, you turn into that color dragon.[2] If you were also wearing a cloak, it will be ripped apart (destroyed). Wearing gray dragon scale mail will prevent the polymorph from happening.
  • If you have lycanthropy, you switch between your animal and were forms.[3]
  • If you are a vampire or vampire bat, you switch between the two.[4]
  • Otherwise, you have a (19-Con)/20 chance of suffering a system shock: you sustain d30 damage and exercise your constitution.

If none of the above happened, you either polymorph into a random monster for 500-999 turns[5], shorter if your polymorphed level is higher than your native level, or if you polymorph into your own race and see: "feel like a new <race>". (this redistributes your attributes and changes your level up or down).

This transformation will destroy your shirt, body armor and cloak if you polymorph into something LARGE or bigger, a non-humanoid MEDIUM or bigger, or a winged gargoyle or marilith (wings and extra arms don't fit).

The trap then disappears.

Monster usageEdit

A user has suggested this page be merged with "the messages here apply generally to monster polymorph, not just poly traps (e.g. chameleons, lycanthropes can generate these). This section needs to be reconciled to [[polymorph]] "

If a monster uses a polymorph trap, you can sometimes hear it from anywhere on the level:

"You hear a thud."
A monster slipped out of its body armor.
"You hear a clank."
A shield or helmet fell to the floor as a monster became handless, tiny or horned.
"You hear a cracking sound."
A monster polymorphed into something too big or the wrong shape for its body armor, and the armor was destroyed.
"You hear a ripping sound."
A monster's shirt or cloak was destroyed as it polymorphed into something too big.

However, these messages can also originate from lycanthropes.

A polymorph trap turns a monster into any of 269 equally likely, non-human, non-limited edition species.[6]

Monsters can resist polymorph traps.[7] Polymorph traps count as a wand for these purposes (level 12).

Monsters may deliberately jump onto polymorph traps or simply step on them.[8] (Strangely, there seems to be nothing in the code to stop powerful monsters deliberately polymorphing, but it's rarely observed.) Even if monsters deliberately jump onto the trap, they still have the large chance to become out-of-depth monsters, as opposed to monsters using items of polymorph.[9]

For this reason, it's safest not to traverse the lower areas of the Gnomish Mines until one has magic resistance and is sufficiently powerful to deal with monsters like Jabberwocks, Liches, and Vampires that can potentially be created with these traps.


If you have valuable armor which you would rather not have destroyed by the trap, you can proceed in relative safety by searching ([s]) every square until you find it. This strategy works best if you have high Luck. Contrary to popular belief, a pair of lenses, intrinsic searching, and Excalibur have no effect on finding traps. Characters with low Luck may have to search many times to reveal an adjacent trap -- see luckstone, sacrifice, altar, and unicorn how to improve your Luck. A crystal ball or confused scroll of gold detection will reliably reveal the location of polymorph traps on the level, although a crystal ball is not safe to use with low intelligence. A wand of secret door detection may be zapped in rooms to determine if a polymorph trap is present; the spell of detect unseen has the same effect.

If you do not have magic resistance, there are other ways to reliably protect yourself from polymorph traps. Wearing a ring of polymorph control is good protection against polymorph traps, as you can always choose a safe form into which to polymorph. An amulet of unchanging will also protect you from transforming. Wearing disposeable junk armor while searching the level is a less desireable alternative if you must explore below dungeon level 7 without magic resistance.

The presence of out-of-depth monsters, or unusual, Gehennom-only, or non-randomly generated monsters such as woodchucks, is a likely indicator of a polymorph trap on the level. If several unusual monsters are grouped in a single area a polymorph trap is almost certainly nearby; check this with telepathy. Proceed with caution.

If you are immune to being polymorphed, you can displace your pet onto the trap to have it turn into a random monster. You can keep doing this until your pet is something useful or powerful, or turns into a (baby) gray dragon, at which point it too is magic resistant, and is no longer affected by the trap. If you aren't immune to being polymorphed, consider using a leash on your pet and standing next to a polymorph trap. Chances for a pet to walk over the trap are much higher this way. Another way is to push boulders to make a two square trap and thus forcing your pet to move between trap and an empty space. After a desirable morph is reached, you can block the trap with a boulder.

You can also use a magic whistle to make your pet land on the trap until you get a desirable morph or a gray dragon. Combine the polymorph trap and magic whistle with some pet treats like tripe or a horse friendly treat like an apple and you can get a pretty nice pet. Note: pets that eat in your presence tend to stay tame longer. The winged gargoyle is a great pet, but it doesn't eat. Standing on the trap and displacing the correct pet onto it works best. Each move, you have 6/7 chance of swapping places, (never if it's a long worm or you punished)[10], 1/7 chance if it is sessile.[11]

Note that if you have neither magic resistance nor a magic whistle, you have no way to cause a sessile pet to be polymorphed by the trap; generating one of these (such as a blue jelly), would end the attempt, but at least protect the trap from other monsters.

Polymorph traps are a resource, but they can also be quite dangerous if you leave them lying around unprotected (some weak but intelligent monsters will willingly jump into the trap in order to become something stronger (luckily including pets), which can be A Bad Thing depending on how stronger it becomes). You can protect a polymorph trap by dropping an item and engraving Elbereth on it. This should prevent monsters from stepping onto the trap. Alternatively, if you don't have protection from the trap, you can drop an item and engrave Elbereth on each tile adjacent to the trap. You can also dig down on the polymorph trap with a pick-axe: since only one trap can exist on a square, the resultant pit will remove the polymorph trap.

Source code referencesEdit

  1. mklev.c, line 1231: polymorph traps not generated above level 8
  2. trap.c, line 266: dragon armor polymorph
  3. trap.c, line 277: lycanthrope polymorph
  4. trap.c, line 282: vampire bat polymorph
  5. polyself.c, line 396, Polyself.c#line452: time-out for polymorph
  6. Trap.c#line2121, Mon.c#line2412, Mon.c#line2376
  7. trap.c, line 1253: monsters may resist polymorph traps
  8. Muse.c#find_misc, Muse.c#use_misc, Monmove.c#line1049
  9. Muse.c#line1789
  10. Uhitm.c#line318
  11. Uhitm.c#line338

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