Upon raising the first and second serpents of fire, the initiate has begun the process of elaborating the Body of Liberation. This is the solar vital body, which is the tetra-dimensional aspect of the physical body, formed within the initiate much like a chick develops within an egg (representing the "carcass" or lunar physical body we all possess). This solar vehicle, Bodhichitta or Soma Psuchikon (the "psychic-image-body") is perfected through the serpents of light and the annihilation of the ego.
Synthetically speaking, we state that even our physical body must become soul. This is when the fire of the first and second serpents are raised: we create a type of flesh which is immortal within the superior dimensions of space, unseen within our physicality except through the eyes of an awakened consciousness. For more information, please study the following course, specifically: