I see 9 as being, in a sense, the most self-identical (i.e., with the unconscious), in the way Nature is, caught in the sleep of pure being, this perhaps being the reason why Riso & Hudson designated 9 as the 'most withdrawn type' (seeing as 4 and 5 are at least already one step removed or estranged by reason of their each having a relatively consolidated ego, which serves as the Archimedean point from which to conceive of a 'self' relative to an 'other'), and why the 9 is driven by a ritual-compulsion to self-alienate, either by falsely identifying with their head and heart centers internally or with others externally, as a way to potentiate the necessary rupturing of the wholeness that has outlived its season (as 'the self discovers itself only in alienation') and make real enough the sense of duality needed for the capacity to look back at, and so identify, the self... that is, if they do manage to find their way back to themselves amidst the thicket.
For this reason, I take the 9's journey to be analogous to the uroboros, its position at the crown coinciding with the point where the mouth eats the tail, both representing the essential undifferentiated state, from which the 9 must emerge by traversing the length of the body—that is, by a process of separation—until it has developed the capacity for differentiation sufficiently enough for it to be able to 'make head or tail' of the apparently identical beginning (merged) and end (connected) state, thereby checking the slothful reflex to slip back and conflate merging with connection, and potentiating its harmonious, forward return.
Furthermore, it seems to me that if 5 and 4, in view of their 'inborn levitation,' are concerned with the substantiation of spirit (in the form of 'insight' and 'image' respectively)—that is, cultivating abstract depth so as to ultimately be tantamount to concrete density, then 9 is the total opposite—concerned with the spiritualization of substance, inasmuch as it is from the start submerged in the 'inner earth' (withdrawn-gut), its modus being to sound out and so lift the 'inner sense-impressions' out of the muffled morass of the body and into the ether, into the light, as best put by Rilke: "earth / isn't this what you want: to resurrect / in us invisibly?"—and so to finally attain to the stars.
