In searching the internet on fertile void, I see that...
Yang fertile void: luminous emptiness
Most sites use it in the solar or yang sense, as the emptiness full of the world.
This is a fertile void. It is the luminous emptiness form arises within and as. It is the Ground of seeing and seen, absent of I anywhere.
It is what we sense before realized selflessness, and what is clearly revealed in realized selflessness.
Yin fertile void: dark womb
But it can also be used in a lunar or yin sense, which is what I fell into yesterday.
This fertile void is a velvety, soft, deeply silent, almost sensual full blackness. A dark womb. A yin ground, slightly into the world of form.
It is a womb that holds anything arising, allowing it to soften, unwind, unravel in whatever way it needs to.
And it is really experienced as black. It is not a clever metaphor, but a direct experience. A velvety blackness as the ground of the physical body and all experience. Holding, allowing it all, as a dark womb, a silent, full black space.
A while back, I learned (and practices regularly for a while) a taoist yoga practice where we visualize golden light coming down the central channel from a point above the head, and a velvety blackness coming up the same channel from the sacrum.
This is that same velvety blackness, although now everywhere.
This velvety blackness seems to be the ground or fabric of existence, as much as the luminous emptiness.