Nokkers

Nokkers are unknown creatures that were created to impede Fushi's progress in preserving the world. The Beholder named them "Nokkers" because they "Knock on the doors of paradise, seeking its destruction."
A Nokker's main form resembles long, presumably sharp, vines. However, they adapt to their environment and take on various other forms - forms stolen from Fushi. Each time a Nokker is defeated they are said to come back stronger each time.