Alarm trap

Version 0.26: This article may not be up to date for the latest stable release of Crawl.

A trap that creates a loud noise to attract nearby monsters. In addition to the noise it creates, it will apply an enchantment making monsters all over the level aware of your location. Hostile monsters may trigger this trap themselves to invoke its effects against you, but your allies will avoid stepping on it.

An alarm trap is a trap which produces a loud noise (intensity 40, louder than Shatter) when stepped on by either you or a monster, alerting anything nearby. It also afflicts you with the Sentinel's Mark status effect (ignores willpower). Like all traps, alarm traps can be set off even by flying beings. After triggering once, they disappear.

Alarm traps cannot be disarmed, but they can be silenced:

The alarm trap vibrates slightly, failing to make a sound.

Silence does not prevent the Sentinel's Mark, though.

Strategy

• Being silenced reduces the number of creatures you lure to you significantly; enemies you haven't seen yet are usually asleep, and only the few wandering opponents on the floor will come to you. Of course, if you then proceed to fight them all near unexplored territory, it's possible you'll wake up more.
• Stepping on the trap and then quickly rushing upstairs to a cleared floor will still likely awaken several opponents, but they won't be able to swarm you en masse nearly so easily.
• Quaffing a potion of cancellation removes Sentinel's Mark immediately, and the awakened opponents mostly lose their ability to track you immediately, though these items are somewhat rare.
• If all else fails and you need to make a last stand, you'll usually have a few turns free before the hoard arrives; consider using that time to create a killhole, and don't be afraid to teleport if it's clearly going badly for you; all those enemies clustered around your old location will need a lot of time to catch up with you, during which you might be able to escape the floor or lose the status effect naturally.
• You can use the trap on an almost cleared floor to lure all remaining monsters to you or to check that there are no monsters left.

History

• Prior to 0.23, alarm traps didn't Mark the player when monsters stepped on them. Also, monsters could trigger these traps while out of the player's line of sight.
• Prior to 0.12, alarm traps could activate multiple times before breaking, but they were not quite as loud and did not afflict you with the Sentinel's Mark.