Poison cloud

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Poison clouds, sometimes known as stinking clouds, are a dungeon feature that appear in NetHack. Like normal clouds, they block line of sight while allowing you, other monsters, projectiles and spells to pass through them unobstructed. However, poison clouds are much more dangerous to walk through.

The area covered by a poison cloud is represented by #Cloud.png - poison clouds are only displayed when actually in your line of sight, whereas regular clouds remain mapped even while blind.


Poison clouds occur naturally in the Plane of Fire, where the lava produces plumes of poison gas intermittently.

Poison clouds can also be created through the following methods:

The following information pertains to an upcoming version (NetHack 3.7.0). If this version is now released, please verify that it is still accurate, then update the page to incorporate this information.

Hezrou leave poisonous clouds behind as they move. Per commit 4b52537, vrocks can now emit a plume of poison clouds when fleeing, similar to the scroll of stinking cloud.


Poison clouds obstruct vision from the outside, and being caught within one can be deadly - walking through them renders you blind and inflicts steady damage each turn you remain inside, eventually killing you unless you can make you way out. Monsters are subjected to those same effects, taking damage unless they are nonliving or unbreathing, and monsters with eyes are blinded - possessing poison resistance will prevent you or a monster from taking any damage, but the gas will still blind and induce coughing regardless.[1]


While you will generally encounter a source of poison resistance far before you have to deal with poison clouds, they can still leave you blinded, which can be a hassle unless you have a means to cure it and/or a way to maintain sight of hostile monsters, such as telepathy or warning.

The following information pertains to an upcoming version (NetHack 3.7.0). If this version is now released, please verify that it is still accurate, then update the page to incorporate this information.

Wearing a wet towel halves damage from poison gas clouds and breath.


Poison clouds were introduced with the scroll of stinking cloud in NetHack 3.3.0.

In NetHack 3.4.3, poison clouds are subject to some now-fixed bugs:

  • Monsters affected by stinking clouds always get angry at you, even if you did not create the cloud. This is bug C341-1 and was declared fixed in January 2004; while 3.4.3 had mostly fixed the bug, it would still occur if loading a bones file from an older game in the 3.4 series.
  • The display of stinking clouds on the map may be incorrect when wearing the Eyes of the Overworld. This is bug C343-213 and was fixed on September 21, 2006.
  • The invulnerability granted from a successful prayer does not prevent damage from poison clouds. This is bug #H2645 according to the commit that fixed it (0add5217), and the fix was made in 2012.


Something is burning your <lungs>! You cough and spit blood!
You are affected by a poison cloud and do not have poison resistance.
You cough.
As above, but you are poison resistant and take no damage from the poison cloud.
Your eyes sting!
You were blinded by the poison cloud.
<monster> coughs!
A breathing, living monster is affected by the stinking cloud. This message is printed regardless of whether or not they possess poison resistance.


The Itlachiayaque patch, which replaces the Archeologist quest artifact with Itlachiayaque and is implemented in some form in many variants, can be #invoked to create a targeted, seven-tile diameter poison cloud, similar to a blessed scroll of stinking cloud.


GruntHack fixes the 3.4.3 prayer-related bug that did not prevent damage from poison clouds.


In UnNetHack, dungeon fern spores primarily attack by exploding into small poison clouds, which can sometimes be avoided by standing diagonally to them. Dungeon ferns and their sprouts can create these spores, as does reading a blessed scroll of stinking cloud while confused. A bag of tricks also has a 140 chance of producing a posion cloud when applied.

Cthulhu will disintegrate into a mass of poison clouds when defeated, but will reform again after a short amount of turns.


In dNetHack, the lair of the Avatar of Lolth has permanent poison clouds that lack gravity or a floor; a character that enters them will be subject to the same movement rules as on the Plane of Air.

More monsters utilize poison clouds as well:

  • The poison gas mage spell used by Cuprilach Rilmani creates clouds of poison gas.
  • Yochlols can transform into a vortex form called a "stinking cloud", which has an engulfing attack with the same effects as regular poison clouds.
  • Changed that fall below 12 HP will stop restoring health naturally and begin releasing small poison clouds, losing 1 HP per turn - this ensures the changed will eventually die, which produces a large cloud of poison.
  • As in UnNetHack, Cthulhu will disintegrate into a mass of poison clouds if defeated, but reforms after a short amount of turns.


In DynaHack, the bag of tricks works as it does in UnNetHack, including the chance of producing poison clouds on application.


In xNetHack, hezrou leave poisonous clouds as they move, reflecting their encyclopedia entry. The Archeologist quest nemesis will use Itlachiayaque to summon poison clouds around you.

Stinking clouds created by reading a scroll no longer use a predefined rhombus shape, and instead expand from their origin point to fit the terrain. This makes them even more dangerous in closed spaces.


In EvilHack, hezrou also leave poisonous clouds as they move. Monsters will also read the scroll of stinking cloud.