From Pathfinder Dark Archive (Remastered), which isn't enabled.

Constricting Hall

COMPLEX HAZARD 8

Stealth +21

Description A hall's four walls become fluid and elastic when a creature reaches the hall's midpoint.

Disable DC 28 Thievery (trained) to stabilize each wall, or Dispel Magic (4th rank; counteract DC 26) to counteract each wall

Lose Form (occult)

Trigger A creature reaches the hall's midpoint

Effect The hall's walls lose their rigidity, becoming fluid and elastic. The hall becomes difficult terrain, and each creature in the hall is knocked Prone unless they succeed at a DC 26 Reflex save. The trap then rolls initiative.

Melee Wall +20, Damage 2d10+11 bludgeoning

Routine (4 actions) This trap loses 1 action each round for each wall that has been disabled. Each wall uses 1 action to slam back and forth rapidly, pummeling one creature in the hall with a wall Strike. On a hit, the target is additionally knocked Prone. The walls distribute the attacks as evenly as possible among creatures in the hall, and the Strikes don't apply the trap's multiple attack penalty.

Reset The trap resets after 1 hour.

Pathfinder Dark Archive (Remastered)ORC