We have thus fully clarified the reason for the diminishment of the structural heights, one below the other, in the course of the development of the partzufim, each lower partzuf forming from the other preceding, upper partzuf. This formation occurs because the beating of the surrounding light on the inner light, which occurs in every partzuf, always obliterates the traces of opacity (ovyut) of the last level that are within the partition.
Why Each Successive Partzuf Diminishes in Size
Petichah LeChokhmat HaKabbalah 42:1