The description for the Lesser Battlebriar is the same as the Blood-Thorn, word for word.
[hide= Suggested description? From the Monster Manual entry]
This six-legged lionlike creature has a body made of writhing vines and thorns. Each of its gorillalike pairs of limbs is slightly shorter than the pair in front of it—its forelimbs are the longest, the middle pair of limbs slightly shorter, and its
rear pair of legs the shortest of all. Long thorns protrude from
every part of the creature’s body, making it seem impossible to approach or move around the creature without risking serious injury. [/hide]
Also since we can't do things like thorn field or impale abilities with nwn restrictions it might be fitting if the battlebriars had a little 1d4 piercing damage shield like punisher barbarians to better fit the whole thorny living siege engine thing ^^