I'm interested in sources discussing magical or spiritual work with darkness - meaning actual physical darkness, not as a metaphor for curses/destructive magic/necromancy etc etc. (The stuff that comes up in the Library when you search "Darkness" all seems to be metphorical - I did have a look at Thomas Chaote's Void Magic).
I'm interested in it more as a something like an elemental force, a subject of contemplation, and a component of ritual. Although silence is just the absence of sound, it has magical and spiritual power and there are philosophical treatise on it - like that but for darkness.
Any suggestions?
(I already have Dawning of Clear Light: A Western Approach to Tibetan Dark Retreat Meditation by Martin Lowenthal. I also think the Ursula LeGuin book Tombs of Atuan is deeply relevant, as so much of it is the priestess protagonist learning to navigate the pitch-black labyrinth under her temple, which it's forbidden to bring light into)
The factual Darkness is the foundation of my entire praxis and my personal god-concept - in yogic terms, I think it would translate as the "subject" of my Samyama.
Despite all that, though, I'm not sure how useful I can be in this case. I don't know of any literary sources that elaborate on the Darkness in the way that you are looking for, and I definitely have nothing to share in a ritual context as a non-ritualist.
I learned to pursue the Darkness from a Bardonian framework, and any work I do with it is done directly.
But you did mention seeking information on it as an Elementary force, though, so perhaps I can elaborate in that direction.
Coincidentally, your wording is actually quite suiting here in the first place, as it is a sort of (sub) Element.
The Darkness, in its fundamental form, is a finer force than the traditional Elements though - it sits above them, as a direct sub-manifestation of the Magnetic Fluid. So if it is the literal Darkness you are after, you will inadvertently find yourself engaging with the Magnetic Fluid.
Before the four Elements, came the two fundamental fluids, the Electric and Magnetic, and from those two forces, Light and Darkness emerged. They are the direct manifestations of the Electro-Magnetic Fluids' respective polar force, and are thus the principal avatars of the Positive and Negative Polarities.
But it is also important to understand that Light and Darkness are not necessarily synonymous with the Electro-Magnetic Fluids themselves. The Darkness is fundamentally Magnetic, and if you were to accumulate it as a force, you would end up accumulating the Magnetic Fluid as well(and vice versa for Light and the Electric Fluid), but on the other hand, one can accumulate the Magnetic Fluid without necessarily accumulating the Darkness, and vice versa again for Light and the Electric Fluid.
Darkness is a
consequence of the Magnetic Fluid and thus always possesses the Magnetic Fluid within itself, but the Magnetic Fluid can exist independently of the Darkness(and so on).
It is a similar situation as the Water and Fire Elements, both being a product of their respective Fluid and possessing said Fluid within themself, but the Fluids still existing independently of their Elements.
The difference though, is that Light and Darkness are finer, more fundamental manifestations of the Fluids which exist in closer conjunction to them in comparison to the Elements, which are more crude and distant products of the Fluids.
Now I could spend all day writing an essay about all the nuances of Darkness, Light, and the Fluids (I haven't even mentioned the complex interplay of Dark and Light within the Elements and the Fluids themselves), but I digress.
With all this in mind, you can certainly work with the Darkness as a tangible force just like any other if you wish, because it actually is a factual force, not just a philosophical concept.
I don't know what purpose you may have for that, but it's not my business.
I only warn you that effectively invoking the Darkness will stimulate your Subconscious, Ego, and other Negative components or qualities, which can be dangerous.