Thus it descended level by level. Each time, what remained of the initial perfection became less and less, for this is precisely what the concealment caused, until in the end, only a modicum of the initial perfection remained, while the deficiency was so great that actual evil started to develop. Nevertheless, what is able to emerge from it is only the beginning of evil. With further intensification of the concealment level by level, the deficiency eventually becomes so great that actual evil comes into being, this being the very opposite of perfection, as stated above.
The Gradual Descent from Perfection Through Veils of Light
Kalach Pitchei Chokhmah 30:39