Trap

Version 0.29: 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:

• 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 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.
• 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 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 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.
• 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. Webs on the floor are permanent, while those created by Ensnare or jumping spiders are 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:

• Permanent teleport traps, which have the same effect as regular teleport traps but are not destroyed when triggered.
• 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 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.

Exploration Traps (Sourceless Malevolence)

When exploring new tiles that haven't been seen before, there is a depth-based chance that the player will trigger an exploration trap from a sourceless malevolence. There are three types of 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. See Shaft#Exploration Shafts for when they can and can not trigger.
• 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 with at least 1* of piety 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 Orcish Mines Elven Halls	2/9
Swamp / Shoals Snake Pit / Spider Nest Slime:1-2	2/9
Slime:3-5 Vaults Crypt Tomb Depths	3/9
Pandemonium Vestible of Hell Hell Branch:1	3/9
Hell Branch: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.

• Mechanical traps were all removed in 0.27.
  • Arrow traps.
  • Blade traps.
  • Bolt traps.
  • Dart traps.
  • Spear traps.
  • Needle traps were replaced with dart traps in 0.24.
  • Axe traps were removed in 0.11.
• Shadow traps were added in 0.16 and removed in 0.17.
• Gas traps were removed in 0.13.

History

• In 0.29, exploration shaft traps in the Dungeon branch will now try and
• In 0.28, exploration shaft traps are restricted to once per branch. In addtion, exploration traps were renamed to sourceless malevolence.
• Prior to 0.25, monsters couldn't spawn on top of traps. As a result, Animate Dead had no effect on corpses that were on tiles with webs. Also, scrolls of magic mapping didn't reveal traps.
• In 0.24, exploration trap effects were made to only pick from eligible exploration effects.
• In 0.23, traps were reworked. Prior to this version:
  • Exploration traps did not exist. Instead, physical traps were often hidden from the player, with an XL-based chance to be detected. Ashenzari increased the trap detection chance.
  • Alarm and net traps did not effect the player if a monster stepped on them.
  • Monsters could trigger physical traps, even if they were outside of the player's line of sight.
  • The trap layout in areas like hall of Zot in Zot:5 and the Tomb were 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).
• Prior to 0.11, trap damage scaled with the floor's depth.