The standard woodland topiary goblin, commonly known as a nyert, is an annoying magical pest. Evolution has granted them bodies that resemble the shrubs and bushes that line the pathways of forests in which they dwell, making them difficult to notice to the untrained eye. Of course, unprepared travelers won't have much trouble seeing them in the end, not when a swarm of the little buggers suddenly lunge out at them with their glowing red eyes and sharp carnivorous fangs. Granted, said travelers won't see much past that.
The one very key advantage people have is that nyerts are relatively small creatures. Single, unready travelers are at risk in most unpopulated forests, but any reasonable group of people won't have much trouble chasing them off. And "unready" is a fairly extreme definition in this case anyway, since it doesn't take much to just kick the durn things if you're waiting for them.