Wall of thorns

Wall of thorns is a conjuration spell that calls a dense, thorny thicket into existence.

Effect
The wall of thorns spell creates a barrier of very tough, pliable, tangled brush bearing needle-sharp thorns as long as a person’s finger. Any creature forced into or attempting to move through the wall of thorns takes 25 points of damage per round of movement, minus 1 point for each point of the creature’s AC. Dexterity bonuses to AC and dodge bonuses do not count for this calculation. (Creatures with an Armor Class of 25 or higher take no damage from contact with the wall.)

You can make the wall as thin as 5 feet thick, which allows you to shape the wall as a number of 10-by-10-by-5-foot blocks equal to caster level XX. This has no effect on the damage inflicted by the thorns, but any creature attempting to break through takes that much less time to force its way through the barrier.

Creatures can force their way slowly through the wall. To make any progress, a creature must succeed at a Strength check (DC 20). A successful creature moves a number of feet equal to its Strength check result minus 19, so a creature who rolled 24 on its Strength check could move 5 feet in a round. Of course, moving or attempting to move through the thorns incurs damage as described above. A creature trapped in the thorns can choose to remain motionless in order to avoid taking any more damage.

Any creature within the area of the spell when it is cast takes damage as if it had moved into the wall and is caught inside. In order to escape, it must attempt to push its way free, or it can wait until the spell ends. Creatures with the ability to pass through overgrown areas unhindered can pass through a wall of thorns at their normal speed without taking damage.

A wall of thorns can be carefully breached by slow work with edged weapons. Chopping away at the wall creates a safe passage 1 foot deep for every 10 minutes of work. Normal fire cannot harm the barrier, but magical fire burns away the barrier in 10 minutes.