Improved Combat Maneuver (dirty trick) ; Constrictor's Grasp, Enveloping Grip, Grappler, or Snag species trait
Description :
Benefit: When you perform a successful dirty trick combat maneuver as a melee attack and the target gains the entangled condition as a result, you can choose to have the affected target be unable to move from its square until it takes the move action to end the condition, but the condition ends immediately if the target is no longer within your reach. In addition, you gain a +4 circumstance bonus to grapple a creature entangled due to your dirty trick.