This 3-minute video from Monadic Media features an explanation of the Causal Body by Michael Robbins.
The causal body is an aspect of the constitution of the human being taking its place between the personality below, so to speak, and the monad or spirit above. The causal body has many names [including] the Temple of Solomon and the egoic lotus.
The causal body is a semi-permanent vehicle on the higher mental plane and is the source of the reincarnational impulse.”