Barbed Wire CR 4
Any creature moving through a square containing barbed wire takes 1d4 points of piercing damage for each 5 feet of movement through the area. In addition, each creature trying to move through barbed wire must succeed at a DC 20 Reflex save or gain the entangled condition. Entangled creatures can try to break free of the barbed wire as a full round action with a successful DC 20 Strength check or Escape Artist check. A creature trapped in barbed wire can opt to remain motionless in order to avoid taking any more damage. A creature can try to pick its way slowly through a field of barbed wire without taking damage or risking entanglement by attempting a Dexterity check as a full round action. For every 5 points by which the check exceeds 10, the creature can move 5 feet (up to its normal land speed).
Pathfinder Adventure Path #71: Rasputin Must Die! © 2013, Paizo Publishing, LLC; Author: Brandon Hodge.