Thornwood (Stronghold Augmentation)

Thornwood: This augmentation can only be added to walls of wood or living wood. Creatures who attempt to climb or are forced into thornwood suffer damage as if it were a wall of thorns. This augmentation does not allow creatures to force their way through the wall (unlike wall of thorns). Magical fire burns away the thornwood augmentation, though it naturally grows back in 24 hours.
Caster Level: 9th; Prerequisites: Craft Wondrous Item, wall of thorns; Market Price: 15,000 gp.