Coiled

[Leanne]

In the twilight of a sibilant heart
spinning mouths
embroider a silken embrace
from the sky of impersonated longing.
Eggshell gestures
barter cankered covenants
as the snarling flint of skin
grinds against the whetstone of lustful danger.
When pain becomes a broken hunger
who is the lover, and who is the knife?

OK, I spotted your explanatory comment but I'm trying to avoid it and I'm not going to do the line-by-line here, because a linear reading of this is not actually going to work for me at all. It's the impressions that bounce around which give it strength, as each new image plays off something before and shifts it, in a way acting to accentuate the coil.

The combined imagery of the knife and the serpents led me to think of the caduceus, which carries so many wonderful connotations including deception and writing, but you mention the orobouros, which of course I probably should have thought of, even though you use twilight and I'd normally associate it with dawn. That in itself is significant to me, as twilight is in the devouring process rather than the point of renewal, so that places the poem deep in that conflict, as well as hinting at Jung's "feedback" since twilight is the precursor to dreams.

"Impersonated longing" indicates the artificial, perhaps trying to live up to the expectations of what "longing" ought to be, the voice intellectually aware that she should be feeling something more socially acceptable, perhaps. This is further highlighted by "eggshell", a very thin veneer, fragile, over the egg or origin/essence. "Cankered covenants", vows turned malignant but still intrinsic to the flesh. "snarling flint" I am not so keen on, I feel the snarl is out of character with either snake or dagger. Flint is very primal though, it promises a spark, it is brittle but may be easily shaped into tools. I'm not sure if it would be too overblown to try "sparks upon" instead of "grinds against".

The final two lines tie the metaphors together very well, and of course the answer is both and neither. It's symbiotic, or perhaps even parasitic, depending on the viewpoint at any given time.