Difference between revisions of "Trap"

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'''Traps''' (represented by '''[[^]]''') are [[Dungeon features]] that harm characters or [[monster]]s who step on them. They do not appear on the map until detected, except in some vaults. Most traps are magical in nature, but some vaults may also place mechanical ones.
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'''Traps''' (represented by '''[[^]]''') are [[Dungeon features]] that harm the player or [[monster]]s who step on them. There are two types of traps: physical traps which are always revealed to the player, and exploration-triggered traps which are triggered by the player randomly during exploration. Most traps are magical in nature, but some vaults may also place mechanical ones.
  
==Strategy==
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==Physical traps==
Your chance to detect traps depends on your experience level and the distance to the trap, and can be increased by worshiping [[Ashenzari]], and decreased by the [[Blurry Vision]] [[mutation]].
+
Physical traps are always revealed to the player (but not necessarily to monsters). They can only be triggered by the player, or by monsters when they are in [[line of sight]] of the player. Flying creatures trigger traps in the same way as non-flying creatures.
  
[[File:trap_detection.png]]
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There are six types of physical trap that generate randomly throughout the [[Dungeon]] and its branches:
 +
* [[File:Temporary teleport trap.png]] '''[[Teleport trap]]s''', which teleport anything that steps on the trap while in line of sight of the player to a different location on the current level. Destroyed when triggered.
 +
* [[File:Alarm_trap.png]] '''[[Alarm trap]]s''', which make an extremely loud noise and apply [[Sentinel's Mark]] to the player when the player or any monster steps on the trap. Destroyed when triggered.
 +
* [[File:Shaft.png]] '''[[Shaft]]s''', which will cause monsters to fall 1-3 floors to a lower floor in the current branch when a monster steps on the shaft and fails a chance based on their intelligence and hit dice. Players can step on shafts safely, and pressing '''>''' will cause the player to fall through the shaft if they wish. Destroyed when triggered.
 +
* [[File:Dispersal_trap.png]] '''[[Dispersal trap]]s''', which blink the player and all monsters in line of sight of the trap when the player or a monster steps on the trap. These traps are permanent.
 +
* [[File:Zot_trap.png]] '''[[Zot trap]]s''', which cause random harmful effects to the player, possibly including teleporting them, creating dangerous summoned or durably summoned monsters, causing an explosion dealing damage to the player, or invoking dangerous levels of [[magical contamination]], when the player or any monster steps on the trap while in line of sight of the player. When monsters step on the trap, there is only a chance for the player to be affected—this is indicated by the message "The power of Zot is invoked against you!". These traps are permanent.
 +
* [[File:Web.png]] '''Webs''', found most commonly in the [[Spider's Nest]], can cause the player and non-[[List of spiders|spider]] monsters to become trapped and be given the Held status, halving their [[evasion]] and preventing melee and ranged combat. These traps are permanent, with the exception of those created by [[jumping spider]]s, which are temporary and destroyed when the player breaks or blinks out of them.
  
[[Fly]]ing players still trigger traps as normal.
+
There are three more types of physical trap that can only be generated by [[vault]]s, most notably being seen in the [[hall of Zot]] on [[Zot:5]] and the [[Tomb]]:
  
Traps that fire ammunition have a limited supply of ammo.
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* [[File:Teleport_trap.png]] '''Permanent teleport traps''', which have the same effect as regular teleport traps but are not destroyed when triggered.
 +
* [[File:Net_trap.png]] '''[[Net trap]]s''', which fire a [[throwing net]] at the player, with [[to-hit]] dependent on the absolute depth of the trap, when the player or any monster steps on the trap while in line of sight of the player. These traps are triggered 2/3 of the time when stepped on by the player, and are destroyed when triggered.
 +
* [[File:Pressure_plate.png]] '''[[Pressure plate]]s''', which usually release monsters to surround the player when anything steps on the trap in line of sight of the player. The monsters released depend on the branch: in most branches, 8 [[redback]]s will be released. In the [[Snake Pit]], this is replaced by 8 [[black mamba]]s and [[mana viper]]s, and in the [[Realm of Zot]], this is replaced by a "klown kar"—3-8 [[Killer Klown]]s will be released. A few vaults have pressure plates that trigger different effects. These are always destroyed when triggered.
  
Once you have detected a trap, you can (with thoughtful maneuvering) use it to harm or block monsters who are pursuing you. More intelligent monsters are much more likely to avoid them, however.
+
There are five more types of mechanical traps that can be found exclusively in the [[Ossuary]]. With the exception of blade traps, these traps all have a limited number of shots and are destroyed once their shots run out. The player has a 1/4 chance to trigger them when stepping on them, with the exception of blade traps, which are triggered 2/3 of the time.
  
==Trap Mechanics==
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* [[File:Arrow_trap.png]] '''[[Arrow trap]]s''': fire arrows, dealing 1-15 damage to the player, or 1-7 damage to monsters. They have 3-11 shots.
Mechanical traps do not always go off when stepped on. The odds of setting one off are:
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* [[File:Blade_trap.png]] '''[[Blade trap]]s''': swing a large blade, dealing 48-76 damage to the player, or 10-38 damage to monsters. They are never destroyed.
*For traps the player knows about:
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* [[File:Bolt trap.png]] '''[[Bolt trap]]s''': fire bolts, dealing 1-40 damage to the player, or 1-18 damage to monsters. They have 3-11 shots.
**2 in 3 chance for blade and net traps.
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* [[File:Needle_trap.png]] '''[[Needle trap]]s''': fire poisoned [[needle]]s, which may poison the target. They have 3-11 shots.
**1 in 4 chance for all other traps.
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* [[File:Spear_trap.png]] '''[[Spear trap]]s''': fire spears, dealing 1-26 damage to the player, or 1-10 damage to monsters. They have 2-7 shots.
*For traps the player does not know about:
 
**Blade and net traps always go off.
 
**4 in 5 chance for all other traps.
 
  
For monsters, the odds are different:
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==Exploration-triggered traps==
*For traps the monster knows about:
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When exploring new tiles that haven't been seen before, there is a depth-based chance that the player will trigger an exploration trap. There are three types of exploration traps that can be triggered:
**1 in 2 chance for blade and net traps.
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* '''Alarm trap effect''': the same as if the player stepped on an alarm trap; causes an extremely loud noise and [[Sentinel's Mark|marks]] the player. This effect cannot be triggered on D:1 or D:2.
**All other traps always go off.
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* '''Shaft effect''': the same as if the player voluntarily took a physical shaft; causes the player to fall 1-3 floors deeper in the branch with no immediate way to return to the higher floor. This effect cannot be triggered while standing on stairs or some other dungeon features, in the [[Tomb]], [[Pandemonium]], on the last floor of any branch, or on the second-last floor of all branches except the [[Dungeon]], [[Lair]], [[Orc]] and [[Depths]], and you cannot be shafted from a higher floor into the last floor of any branch except the [[Dungeon]], [[Lair]], [[Orc]] or [[Depths]].
*For traps the monster does not know about:
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* '''Teleport effect''': causes you to be teleported to a random location on the current floor that is next to monsters, like the [[teleportitis]] mutation. This effect will fail to trigger if the game cannot find any such locations on the current floor.
**4 in 5 chance for blade traps.
 
**2 in 3 chance for net traps.
 
**All other traps always go off.
 
  
If a mechanical trap is triggered, there is still a chance for the trap's weapon to miss, depending on your [[evasion]] and [[dexterity]]. The [[Repel Missiles]] and [[Deflect Missiles]] spells reduce the chance of a projectile hitting (except for the net trap, which drops the net rather than firing it). If you fail to evade the projectile, but are wearing a [[shield]], you may instead block the projectile.
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Note that new tiles revealed immediately after a shaft or teleport effect won't trigger another trap effect, giving the player a bit of a break post-trap.
  
==Monsters & Traps==
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Worshippers of [[Ashenzari]] are completely immune to these effects.
Different monsters react differently to traps. Most monsters with animalistic intelligence or above will avoid ones they know about, and refuse to cross a trap even if there is no other way to reach you. [[Monster_intelligence|Mindless]] monsters like [[zombie]]s will walk through traps regardless of how much damage it might cause them. [[Zot trap]]s are special: if you're in sight when a hostile monster walks into one, ''you'' get zapped. ("[It] uses the power of Zot against you!")
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 +
===Chance to trigger===
 +
The chance for each of the alarm trap, shaft and teleport traps to trigger when an exploration trap effect is rolled is 1/3 for each.
  
In some situations, monsters already know the locations of traps:
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The chance for a given turn exploring new tiles is:
*Monsters native to a [[dungeon branch]] (eg. [[orc]]s in the [[Orcish Mines]]) already know the locations of all traps in their branch, since they live there.
 
*Monsters friendly to the player, and good neutrals, know the location of all traps that you know about, since it's assumed that you would tell them about the traps.
 
*Monsters with high [[intelligence]] or greater have a 1 in 3 chance of knowing about the existence of any single trap.
 
  
==Trap Types==
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(number of floor tiles revealed on this turn / number of floor tiles on current level) * (1 + absdepth of current level/10) / 9
Notes:
 
*Only teleport, shadow, shaft, alarm and Zot traps are placed randomly.
 
*Shaft traps won't be placed in corridors in the first 7 levels of the dungeon.
 
*The damage caused by mechanical traps is reduced by the player's [[AC]].
 
  
{| class="prettytable"  
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The chance for one or more exploration traps to trigger on a given level is therefore simply <code>(1 + absdepth/10) / 9</code>.
! '''Trap'''
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This leads to the following chances of the game attempting to trigger one or more exploration-triggered traps on any given level:
! '''Description'''
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{| class="prettytable"
! '''Amount of ammo'''
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! Branch !! Chance per floor
! '''Base damage to player'''
 
! '''Base damage to monsters'''
 
! '''Trap type'''
 
 
|-
 
|-
| [[Alarm trap]]
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| D:1-9 || 1/9
| Makes a loud [[noise]] and afflicts you with the [[Sentinel's Mark]] [[status effect]]
 
| N/A
 
| None
 
| None
 
| Magical
 
 
|-
 
|-
| [[Shaft]]
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| D:10-15 || 2/9
| Opens a hole under the victim, sending them to a deeper dungeon level
 
| N/A
 
| None
 
| None
 
| Natural
 
 
|-
 
|-
| [[Teleport trap]]
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| Lair || 2/9
| [[Teleport]]s the victim to a random location on the level
 
| N/A
 
| None
 
| None
 
| Magical
 
 
|-
 
|-
| [[Zot trap]]
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| Orcish Mines || 2/9
| Produces a powerful magical [[miscast effect]]
 
| N/A
 
| Varies by effect
 
| Varies by effect; only affects friendly monsters
 
| Magical
 
 
|-
 
|-
| [[Arrow trap]]
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| Elven Halls || 2/9
| Fires an [[arrow]]
 
| 3 - 11
 
| 1 - 15
 
| 1 - 7
 
| Mechanical
 
 
|-
 
|-
| [[Blade trap]]
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| Swamp/Shoals/Snake Pit/Spider Nest || 2/9
| Swings a huge swinging blade
 
| N/A
 
| 48 - 76
 
| 10 - 38
 
| Mechanical
 
 
|-
 
|-
| [[Bolt trap]]
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| Slime:1-2 || 2/9
| Fires a [[bolt]]
 
| 3 - 11
 
| 1 - 40
 
| 1 - 18
 
| Mechanical
 
 
|-
 
|-
| [[Dart trap]]
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| Slime:3-5 || 3/9
| Fires a [[dart]]
 
| 3 - 11
 
| 1 - 6
 
| 1 - 4
 
| Mechanical
 
 
|-
 
|-
| [[Needle trap]]
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| Vaults || 3/9
| Fires a [[needle|poisoned needle]]
 
| 3 - 11
 
| None, but may [[poison]]
 
| None, but may poison
 
| Mechanical
 
 
|-
 
|-
| [[Net trap]]
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| Depths || 3/9
| Drops a [[throwing net]]
 
| 1
 
| None
 
| None
 
| Mechanical
 
 
|-
 
|-
| [[Pressure plate]]
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| Crypt || 3/9
| Causes ''something'' to happen, usually bad.
 
| N/A
 
| None
 
| None
 
| Mechanical
 
 
|-
 
|-
| [[Spear trap]]
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| Tomb || 3/9
| Fires a [[spear]]
 
| 2 - 7
 
| 1 - 26
 
| 1 - 10
 
| Mechanical
 
 
|-
 
|-
| [[Web]]
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| Pandemonium || 3/9
| Induces the [[held]] status for several turns
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|-
| May break after each use
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| Hell || 3/9
| None
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|-
| None
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| Geh/Coc/Tar/Dis:1 || 3/9
| Mechanical
+
|-
 +
| Geh/Coc/Tar/Dis:2-7 || 4/9
 +
|-
 +
| Zot:1-2 || 3/9
 +
|-
 +
| Zot:3-5 || 4/9
 
|}
 
|}
 +
The above chances are for the game to attempt to trap the player. Given that there are many situations when the shaft and teleport effects can fail, this does not accurately reflect the chance of actually being trapped on a given floor. Situations when a particular trap effect fails are not announced.
  
Note that the "pressure plate" trap is a "software trap"; rather than a fixed result, its effects are scripted in Lua, and might include stuff like dumping out a basket of [[spider]]s, or dropping a grating to block the path behind you.
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<!-- Commented out because I'm not at all convinced that this is correct -- NormalPerson7
 +
==Monsters & Traps==
 +
Different monsters react differently to traps. Most monsters with animalistic intelligence or above will avoid ones they know about, and refuse to cross a trap that is harmful to them even if there is no other way to reach you. [[Monster_intelligence|Mindless]] monsters like [[zombie]]s will walk through traps regardless of how much damage it might cause them.
 +
 
 +
In some situations, monsters already know the locations of traps:
 +
*Monsters native to a [[dungeon branch]] (eg. [[orc]]s in the [[Orcish Mines]]) already know the locations of all traps in their branch, since they live there.
 +
*Monsters friendly to the player, and good neutrals, know the location of all traps, since it's assumed that you would tell them about the traps.
 +
*Monsters with human [[intelligence]] or greater have a 1 in 3 chance of knowing about the existence of any single trap.
 +
-->
  
 
==Obsolete Traps==
 
==Obsolete Traps==
Over the years, many traps have been removed from the game for various reasons. These include:
+
Over the years, many traps have been removed from the game for various reasons.
*'''[[Shadow trap]]s''' (Removed in [[0.17]])
+
* [[File:Shadow_trap.png]] '''[[Shadow trap]]s''' were added in [[0.16]] and removed in [[0.17]].
*'''[[Gas trap]]s''' (Removed in [[0.13]])
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* [[File:Gas_trap.png]] ''' [[Gas trap]]s''' were removed in [[0.13]].
*'''[[Axe trap]]s''' (Removed in [[0.11]])
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* [[File:Axe_trap.png]]''' [[Axe trap]]s''' were removed in [[0.11]].
  
 
==History==
 
==History==
In [[0.23]] a new trap type will appear, the dispersal trap, which blinks everything that can see the trap.
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*In [[0.24]], exploration trap effects will be made to only pick from eligible exploration effects.
 
+
*Dispersal traps were added in [[0.23]]. Prior to [[0.23]], exploration-triggered traps did not exist, and physical traps were not always revealed to the player—instead, the player had an XL-based chance to detect physical traps and so would sometimes stumble into these traps. Worshippers of [[Ashenzari]] had an increased chance to detect these traps. Alarm and net traps did not affect the player when monsters stepped on the trap, and the trap layout in the [[hall of Zot]] in [[Zot:5]] and the [[Tomb]] was very different.
Prior to [[0.16]], flying players and monsters could avoid triggering traps. Shadow traps were added and trap disarming was removed in this version.
+
*Prior to [[0.16]], flying players and monsters could avoid triggering traps. Shadow traps were added and trap disarming was removed in this version.
 
+
*Prior to [[0.15]], mechanical traps dropped ammunition and all teleport traps were permanent.
Prior to [[0.15]], mechanical traps dropped ammunition and all teleport traps were permanent.
+
*Prior to [[0.13]], mechanical traps were randomly placed throughout every branch. Trap detection was based on the [[Traps (skill)|Traps]] skill.
 
+
*Prior to [[0.12]], Traps could be detected by searching (command '''s''').
Prior to [[0.13]], mechanical traps were randomly placed throughout every branch.
 
 
 
Prior to [[0.12]], Traps could be detected by searching (command '''s''').
 
  
 
[[Category:Traps]]
 
[[Category:Traps]]
 +
[[Category:Crystal Ball Articles]]

Revision as of 20:23, 2 July 2019

Version 0.23: This article may not be up to date for the latest stable release of Crawl.

Traps (represented by ^) are Dungeon features that harm the player or monsters who step on them. There are two types of traps: physical traps which are always revealed to the player, and exploration-triggered traps which are triggered by the player randomly during exploration. Most traps are magical in nature, but some vaults may also place mechanical ones.

Physical traps

Physical traps are always revealed to the player (but not necessarily to monsters). They can only be triggered by the player, or by monsters when they are in line of sight of the player. Flying creatures trigger traps in the same way as non-flying creatures.

There are six types of physical trap that generate randomly throughout the Dungeon and its branches:

  • Temporary teleport trap.png Teleport traps, which teleport anything that steps on the trap while in line of sight of the player to a different location on the current level. Destroyed when triggered.
  • Alarm trap.png Alarm traps, which make an extremely loud noise and apply Sentinel's Mark to the player when the player or any monster steps on the trap. Destroyed when triggered.
  • Shaft.png Shafts, which will cause monsters to fall 1-3 floors to a lower floor in the current branch when a monster steps on the shaft and fails a chance based on their intelligence and hit dice. Players can step on shafts safely, and pressing > will cause the player to fall through the shaft if they wish. Destroyed when triggered.
  • Dispersal trap.png Dispersal traps, which blink the player and all monsters in line of sight of the trap when the player or a monster steps on the trap. These traps are permanent.
  • Zot trap.png Zot traps, which cause random harmful effects to the player, possibly including teleporting them, creating dangerous summoned or durably summoned monsters, causing an explosion dealing damage to the player, or invoking dangerous levels of magical contamination, when the player or any monster steps on the trap while in line of sight of the player. When monsters step on the trap, there is only a chance for the player to be affected—this is indicated by the message "The power of Zot is invoked against you!". These traps are permanent.
  • Web.png Webs, found most commonly in the Spider's Nest, can cause the player and non-spider monsters to become trapped and be given the Held status, halving their evasion and preventing melee and ranged combat. These traps are permanent, with the exception of those created by jumping spiders, which are temporary and destroyed when the player breaks or blinks out of them.

There are three more types of physical trap that can only be generated by vaults, most notably being seen in the hall of Zot on Zot:5 and the Tomb:

  • Teleport trap.png Permanent teleport traps, which have the same effect as regular teleport traps but are not destroyed when triggered.
  • Net trap.png Net traps, which fire a throwing net at the player, with to-hit dependent on the absolute depth of the trap, when the player or any monster steps on the trap while in line of sight of the player. These traps are triggered 2/3 of the time when stepped on by the player, and are destroyed when triggered.
  • Pressure plate.png Pressure plates, which usually release monsters to surround the player when anything steps on the trap in line of sight of the player. The monsters released depend on the branch: in most branches, 8 redbacks will be released. In the Snake Pit, this is replaced by 8 black mambas and mana vipers, and in the Realm of Zot, this is replaced by a "klown kar"—3-8 Killer Klowns will be released. A few vaults have pressure plates that trigger different effects. These are always destroyed when triggered.

There are five more types of mechanical traps that can be found exclusively in the Ossuary. With the exception of blade traps, these traps all have a limited number of shots and are destroyed once their shots run out. The player has a 1/4 chance to trigger them when stepping on them, with the exception of blade traps, which are triggered 2/3 of the time.

  • Arrow trap.png Arrow traps: fire arrows, dealing 1-15 damage to the player, or 1-7 damage to monsters. They have 3-11 shots.
  • Blade trap.png Blade traps: swing a large blade, dealing 48-76 damage to the player, or 10-38 damage to monsters. They are never destroyed.
  • Bolt trap.png Bolt traps: fire bolts, dealing 1-40 damage to the player, or 1-18 damage to monsters. They have 3-11 shots.
  • Needle trap.png Needle traps: fire poisoned needles, which may poison the target. They have 3-11 shots.
  • Spear trap.png Spear traps: fire spears, dealing 1-26 damage to the player, or 1-10 damage to monsters. They have 2-7 shots.

Exploration-triggered traps

When exploring new tiles that haven't been seen before, there is a depth-based chance that the player will trigger an exploration trap. There are three types of exploration traps that can be triggered:

  • Alarm trap effect: the same as if the player stepped on an alarm trap; causes an extremely loud noise and marks the player. This effect cannot be triggered on D:1 or D:2.
  • Shaft effect: the same as if the player voluntarily took a physical shaft; causes the player to fall 1-3 floors deeper in the branch with no immediate way to return to the higher floor. This effect cannot be triggered while standing on stairs or some other dungeon features, in the Tomb, Pandemonium, on the last floor of any branch, or on the second-last floor of all branches except the Dungeon, Lair, Orc and Depths, and you cannot be shafted from a higher floor into the last floor of any branch except the Dungeon, Lair, Orc or Depths.
  • Teleport effect: causes you to be teleported to a random location on the current floor that is next to monsters, like the teleportitis mutation. This effect will fail to trigger if the game cannot find any such locations on the current floor.

Note that new tiles revealed immediately after a shaft or teleport effect won't trigger another trap effect, giving the player a bit of a break post-trap.

Worshippers of Ashenzari are completely immune to these effects.

Chance to trigger

The chance for each of the alarm trap, shaft and teleport traps to trigger when an exploration trap effect is rolled is 1/3 for each.

The chance for a given turn exploring new tiles is:

(number of floor tiles revealed on this turn / number of floor tiles on current level) * (1 + absdepth of current level/10) / 9

The chance for one or more exploration traps to trigger on a given level is therefore simply (1 + absdepth/10) / 9. This leads to the following chances of the game attempting to trigger one or more exploration-triggered traps on any given level:

Branch Chance per floor
D:1-9 1/9
D:10-15 2/9
Lair 2/9
Orcish Mines 2/9
Elven Halls 2/9
Swamp/Shoals/Snake Pit/Spider Nest 2/9
Slime:1-2 2/9
Slime:3-5 3/9
Vaults 3/9
Depths 3/9
Crypt 3/9
Tomb 3/9
Pandemonium 3/9
Hell 3/9
Geh/Coc/Tar/Dis:1 3/9
Geh/Coc/Tar/Dis:2-7 4/9
Zot:1-2 3/9
Zot:3-5 4/9

The above chances are for the game to attempt to trap the player. Given that there are many situations when the shaft and teleport effects can fail, this does not accurately reflect the chance of actually being trapped on a given floor. Situations when a particular trap effect fails are not announced.


Obsolete Traps

Over the years, many traps have been removed from the game for various reasons.

History

  • In 0.24, exploration trap effects will be made to only pick from eligible exploration effects.
  • Dispersal traps were added in 0.23. Prior to 0.23, exploration-triggered traps did not exist, and physical traps were not always revealed to the player—instead, the player had an XL-based chance to detect physical traps and so would sometimes stumble into these traps. Worshippers of Ashenzari had an increased chance to detect these traps. Alarm and net traps did not affect the player when monsters stepped on the trap, and the trap layout in the hall of Zot in Zot:5 and the Tomb was very different.
  • Prior to 0.16, flying players and monsters could avoid triggering traps. Shadow traps were added and trap disarming was removed in this version.
  • Prior to 0.15, mechanical traps dropped ammunition and all teleport traps were permanent.
  • Prior to 0.13, mechanical traps were randomly placed throughout every branch. Trap detection was based on the Traps skill.
  • Prior to 0.12, Traps could be detected by searching (command s).