Non duality - must it be transcendent I am exploring non duality. I tend to believe it's true but I'm not sure if I accept the transcendent element. Is it possible that this awareness is simply a deeper level of the mind ? That it's not part of God or a higher power. Not eternal?
From AN10.29:


  Someone perceives the meditation on universal earth above, below, across, non-dual and limitless.
  They perceive the meditation on universal water …
  the meditation on universal fire …
  the meditation on universal air …
  the meditation on universal blue …
  the meditation on universal yellow …
  the meditation on universal red …
  the meditation on universal white …
  the meditation on universal space …
  They perceive the meditation on universal consciousness above, below, across, non-dual and limitless.
  These are the ten universal dimensions of meditation.
  The best of these ten universal dimensions of meditation is when someone perceives the meditation on universal consciousness above, below, across, non-dual and limitless.
  Some sentient beings perceive like this.
  But even the sentient beings who perceive like this decay and perish.


Yes. It is not eternal.

The sutta ends with the Buddha declaring:


  But I do advocate the complete understanding of sensual pleasures, sights, and feelings. And I advocate complete extinguishment by not grasping in this very life, wishless, extinguished, and cooled.”


Regarding transcendance and theories of a self, SN12.2 may be of interest:


  There are these four kinds of grasping.
  Grasping at sensual pleasures, views, precepts and observances, and theories of a self.