Poison cloud

Poison clouds, sometimes known as stinking clouds or fumaroles, are a dungeon feature that appear in NetHack. Like normal clouds, they block line of sight while allowing the hero, monsters, projectiles and spells to pass through them unobstructed—however, they are much more dangerous to walk through and can inflict poison damage.

The area covered by a poison cloud is represented by #—poison clouds are only displayed when actually in the hero's line of sight, whereas regular clouds remain mapped even while blind.

Generation

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 poison breath weapon of a green dragon, an iron golem, or randomly from the Chromatic Dragon
• A read scroll of stinking cloud

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

Hezrou leave single squares of 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.

Per commit fe34d4e3, the Minion of Huhetotl, the Chromatic Dragon and Nalzok create plumes of poison clouds upon death. Per commit 8b9a93f7, the hero will not be blamed for damage done by poison clouds from killing a quest nemesis.

Per commit 9390a844, poison cloud breath attacks no longer cover wall squares as a result of bouncing off them.

Per commit b23ff20c, poison clouds expand around terrain obstacles from their point of origin instead of being a predefined rhombus shape that fails to appear in terrain obstacles. This was taken from xNetHack, so it should be removed from that section below since it will no longer be a difference.

Description

Poison clouds obstruct vision from the outside, and being caught within one can be deadly: walking through them renders the hero blind and inflicts steady poison damage each turn they remain inside, eventually killing them unless they can make their 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 a hero or monster from taking any damage, but the gas will still blind them and induce coughing regardless. Monsters that can fire poison breath are themselves immune to the effects of poison clouds.

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

Wearing a wet towel halves damage from poison clouds.

Per commit 0eb88963, paranoid confirmations cover walking into known poison clouds.

Per commit 086f6810, the player's or a monster's coughs induced by a poison cloud wake up adjacent monsters.

Strategy

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.

History

Poison clouds are introduced with the scroll of stinking cloud in NetHack 3.3.0. From this version to NetHack 3.4.3, including some variants based on those versions, poison clouds do not yet have their own glyph, rays of poison do not leave behind poison clouds, and the Plane of Fire does not emit poison clouds. Additionally, 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 mostly fixes the bug, it can 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, and the fix was made in 2012 via commit 0add5217.

The fumaroles on the Plane of Fire are introduced in NetHack 3.6.0 via commit 71401a7d, which also gives the poison cloud its current glyph and causes them to appear over terrain glyphs.

Poison breath attacks leaving behind trails of poison clouds are added in NetHack 3.6.1 via commit da0e6601, based on an original patch by Leon Arnott. NetHack 3.6.1 also introduces immunity to gas clouds for monsters that breathe poison gas via commit f5c157cb, with the iron golem already being immune as a non-breathing monster.

Messages

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.

Variants

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

GruntHack fixes the NetHack 3.4.3 bug that does not prevent damage from poison clouds while the hero is invulnerable from successful prayer.

UnNetHack

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 ¹⁄₄₀ 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.

dNetHack

In dNetHack, notdNetHack and notnotdNetHack, 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 monster 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 ¹⁄₂ HP will stop restoring health naturally and begin releasing small poison clouds, losing 1 HP per turn—this ensures the changed will eventually die, and they produce a large cloud of poison upon death.
• As in UnNetHack, Cthulhu will disintegrate into a mass of poison clouds if defeated, but reforms after a short amount of turns.

DynaHack

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

xNetHack

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.

EvilHack

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