Needle Hedge

Areas of sharp-needled bushes grow in the dark forests of the Shadowfell and in areas of the world where shadow’s influence is strong. The plants are covered in long, sharp spines and thorns, forcing creatures to slow down as they move through the bushes or suffer a multitude of small cuts.

    Effect: A needle hedge is difficult terrain, and it grants cover to a creature within it or behind it. If a creature moves through more than 1 square of needle hedge during a single move action or incident of forced movement, that creature takes 5 damage per tier.
    Usage: Characters are likely to consider a needle hedge an effectively solid barrier until they’re pushed through it. Use it with monsters that can force movement, or with elves or other skirmishers that can shift freely in difficult terrain (including creatures that have the forest walk ability).

Published in Dungeon Master's Guide 2, page(s) 61.