In Dr. A. Kingford's book Perfect Way there is an explanation of who or what Satan is.

Satan, it says, is the adversary because matter opposes spirit.

“ . . . For Satan is the magistrate of the justice of God (Karma); ...”

“The glory of Satan is the shadow of the Lord”: God in the manifested world; “the throne of Satan is the footstool of Adonai” — that footstool being the whole Kosmos.

When the Church, therefore, curses Satan, it curses the cosmic reflection of God; it anathematizes God made manifest in matter or in the objective; it maledicts God, or the ever-incomprehensible Wisdom, revealing itself as Light and Shadow, good and evil in nature, in the only manner comprehensible to the limited intellect of Man.

http://www.theosociety.org/pasadena/sd/sd2-1-13.htm

See page 235 on the above site.