A monster for M20, it works pretty good as forest boss sorrounded by lesser minions … ready your axe.
Dead Tree (NE)
8HD +20 (HP 40), AC 20, 5/fire, axe, immune to Piercing and ½ damage from blunt, fire and axe deal 2x damage, natural +8/+8/+8 (2D6) (multiple targets)
Evil druids can sometimes choose to became a Dead Tree. In this form they can’t move outside a druidic stones circle but can control evil forest beings as dire animals and sylvans. After the players enter the area a wall of wood rises from the earth, trapping them inside the circle, everyone moving close to the wall get an attack +3 (1d6), the wall can’t be destroyed since it regrows instantly, only the death of the Tree will destroy it. Dead Tree can choose to not attack in melee, that round everyone in the circle will be hit by spikes from the ground, 2D6 damage (save DEX DC 15, no damage).