In many wild forests there is an abundance of undergrowth, a truism shared by the forest beyond the keep's walls. Even in the un-corrupted wilds of our own world, creatures lurk in the undergrowth that are best left undisturbed. The badger's set, the adder's nest and the fire ant's mound all discouraging passage through such places. Yet none of these are quite as deadly as the unnatural horrors lurking in that sickened arboreal maze upon Moonshadow.
A typical example is the pit vine, whose form is that of a pitcher plants buried within the ground. They cover their opening with vines that have been seen to slowly manipulate dirt and fallen leaves into the perfect camouflage for these hungry maws. Whispered rumour suggests that they have also been seen to lash out, and pull nearby explorers inexorably into their embrace.
Upon entering the maw, and being pierced by one of the hundreds of tiny flexible spines on the inside of this beast, total paralysis of ones extremities occurs. This ensures that the victim is poisoned ever more deeply as their limp body is penetrated by yet more spines. No scream shall escape, though victims who have been rescued swiftly have reported being fully awake and fully able to feel the slow creep of the acid upwards as it dissolves leather, cloth and then flesh and bone.
Many who are not rescued before their feet are dissolved are driven mad by the pain. Staying upon the narrow ruined paths is almost mandatory if one wishes to survive in this place, for the pit vines are the least of the horrors that lurk in the undergrowth of Moonshadow's corrupted weald.