Leah — the hind parts of Imma and inner soul of Nukva.
Leah is the inner soul of Nukva, drawn from the hind parts of Imma. Two Nukvas because two kinds of government in the lower realms are required.
Op. 118 closes the Z"N General Principles unit by specifying the structural origin of Leah. The two-Nukvas doctrine is what makes the Op. 117 coupling-modes variability operationally specific.
Leah — the inner soul of Nukva — is drawn from the hind parts of Imma. The cosmogonic source is therefore Imma, but specifically Imma's back-anatomy — her hind parts. This makes Leah structurally connected to Imma at the source while operationally distinct as Nukva's inner aspect.
Rachel is Nukva proper — the primary Partzuf-form. Where Leah is Nukva's inner soul, Rachel is Nukva's visible operational identity.
The two-Nukvas doctrine is structurally required. Two kinds of government in the lower realms: the inner-truth governance (which operates through Jacob + Leah) and the visible governance (which operates through Israel + Rachel — or Zeir Anpin (Z"A) + Rachel). Without two Nukvas, the cosmic government could only operate in one mode at a time; with two, it can operate in different modes for different cycle phases.
Op. 130–138 (the closing Nukva-building unit) operationalises the two-Nukvas doctrine in full detail. Op. 138's eight-stage Coupling order operates with both Nukvas active.