Razorvine

This hardy creeper plant is ubiquitous in Sigil and throughout the planes. It has sharp, serrated leaves that cut creatures moving through the vegetation.

    Effect: Razorvines form in an area that is at least 4 contiguous squares. A razorvine is difficult terrain. A creature that enters a razorvine square or starts its turn there takes 10 damage per tier.
    Usage: Use this terrain to keep the characters out of specific locations in an encounter area, or place a controller or an elite creature within a circle of razorvine, or in a U-shaped section that only allows one character to approach it without going through razorvine squares. Unless the characters have strong ranged attacks, they must choose whether to take damage from the razorvine, or find another way to bypass them.
    Used as part of a trap, razorvine growing from movable wooden or stone walls can block the characters’ retreat from a tough fight.

Published in Manual of the Planes, page(s) 22.