system
A chat on 4chan
human
What you refer to as succubus is a thoughtform. 

Summoning the succubus in modern terminology means creating your neural structure in such a way that when life energies power your whole body, the electricity will flow through the pair of neurons that constitute that thoughtform and subsequently give rise to subconscious lustful thinking, instructing your body to slowly accumulate and transform your valuable bodily nutrients into sperm.

Furthermore, when you sleep, your awareness might slip into the inner mechanics of your body. When you are awake, your perception is tuned to the electric signals of your outer sensory organs. When you sleep/dream, your perception is tuned to the electric signals while your body is defragmenting memory, organizing things. It is then, that you can 'dream' a succubus teasing you and sexually pleasing you, all while you were perceiving the autonomous function of the body to expel excess sperm that accumulated. The observer will 'perceive' that using symbols of the culture he was grown into.

What people call demons, archons, whatever are just thoughtforms and subconscious processes, living somewhere within your neurological structure of the body. Even a program/subroutine that works in the background of an operating system is called a DAEMON.
gpt
I've met a real succ before. They are real. Although a lot of people probably jerk off to their imagined version of a succ as opposed to a real one.