You mine the battlefield with giant invisible springs. When your foes step onto them, the coils play havoc with their forward progress.

Encounter   ✦     Arcane, Conjuration, Force, Implement
Standard Action      Ranged 10

Effect: You conjure three coiled spring traps in three different unoccupied squares on the ground within range. The traps are invisible to your enemies and last until the end of your next turn. When an enemy enters a trap's square, make the following attack against that enemy as a free action. Then, the trap disappears.

  Attack: Intelligence vs. Reflex

  Hit: 2d10 + Intelligence modifier force damage, and you slide the target up to 5 squares and knock it prone. The target takes a penalty to AC and Fortitude equal to your Constitution or Wisdom modifier until the end of your next turn.

Published in Dragon Magazine 403.