The Treant is immobile as it is firmly rooted to the ground.
It is classified as a Huge monster, which means that both ground and aerial attackers can inflict damage upon it. As it is a creature composed of wood, it is highly vulnerable to Flame-based attacks. The Treant is also capable of summoning Worms to help protect itself and to attack the party. Killing all the Worms it has summoned will render it more vulnerable to damage.