Collapsing Tunnel
Level 13 Lurker
XP 800

An alchemical explosion causes a tunnel to collapse.

Trap: When triggered, the rock of the collapsing shaft fills the area with attacks.Perception     DC 18: The character sees a tripwire that activates the collapse.     DC 23: The character notices tripwires running across the mine tracks, allowing them to be triggered by rolling a mine cart across them.Initiative +3TriggerThe trap is triggered when a creature or mine cart moves through the squares where the tripwire is laid. When triggered, the trap rolls initiative. Between the trigger and the attack, characters in the area know that the tunnel is collapsing. On its turn, the collapsing tunnel attacks a random square in the encounter areaAttackTarget: All creatures in burstAttack: +16 vs. ReflexHit: 2d12 + 8 damageMiss: Half damageEffect The burst area becomes difficult terrain.Sustain Standard The collapsing tunnel attacks each round until it has attacked every square in the area.Countermeasures     Athletics DC 5 or Athletics (without a running start) DC 10: A character who makes a successful check can jump over the tripwire without triggering it.
     Thievery DC 18: A character adjacent to the tripwire can delay the trap with a successful check.
     Thievery DC 23: A character adjacent to the tripwire can disable the trap with a successful check.
     Strength DC 23: If an opponent attempts to trigger the trap with a mine cart, a character adjacent to the cart can attempt to stop or derail it with a successful check.
     Dungeoneering DC 23: A character who makes a successful check (a minor action) can determine the area the trap will attack on its next turn.

Published in Dungeon Magazine 157, page(s) 62.