Yetzirah (יצירה) is the formative world, where things are designed. It is the sphere of angels. In both the systems of four and five Souls, it is Ruach, the Intellect.
In the Tetragrammaton (יהוה), Yetzirah corresponds to Vau, the Nail. Its attributions are air, and the Tarot Swords (also its Princes — Knights
in classical decks).
The worlds are separated from one another by veils
. Above, Yetzirah is separated from
Briah by the Abyss, and below, it is separated from Assiah
by the Veil of the Profane. Moreover, within this world there is another veil,
the veil-that-is-not-a-veil Paroketh that separates the Astral Triad
from the Ethical Triad.