False-Floor Pit (Elite)
Level 1 Elite Warder
XP 200

A covered pit is hidden near the center of the room. Timber covered with flagstones is rigged to fall when a creature walks on it, dropping the creature into a 20-foot-deep pit with poisoned spikes.

Trap: A 2-by-2 section of the floor hides a 20-foot-deep pit with poisoned spikes.Perception     DC 22: The character notices the false stonework.TriggerThe trap attacks when a creature enters on of the trap's four squares.AttackImmediate Reaction      Melee
Target: The creature that triggered the trap.Attack: +4 vs. ReflexHit: Target falls into pit, takes 3d10 damage + ongoing 5 poison damage (save ends), and falls prone.Miss: Target returns to the last square it occupied and its move action ends immediately.Effect: The false floor opens and the pit is no longer hidden.Countermeasures     Thievery DC 12: An adjacent character can trigger the trap with a successful check (standard action). The floor falls into the pit.
     Thievery DC 27: An adjacent character can disable the trap with a successful check (standard action). The floor becomes safe.
     Athletics DC 11 or Athletics (without running start) DC 21: A character who makes an successful check can jump over the pit.
     Athletics DC 15: A character can climb out with a successful check.

Published in Dungeon Master's Guide, page(s) 87.