The difference between the Dew of Bedolach and the Unknown Head.
The Dew of Bedolach descends from A"A's head and contains all colours. radla is unspecifiable in principle. The contrast sharpens what kind of uncertainty radla holds.
Op. 89 closes the Unknown Head unit by sharpening radla's character through contrast with another concealed-cosmic structure: the Dew of Bedolach (tala de-bedolacha) — the white crystal-like dew that descends from A"A's head per Idra Rabba, in which all colours are seen.
Both the Dew of Bedolach and radla are concealed. But their concealment is different in kind.
The Dew is specifiable in retrospect. After the dew descends from A"A's head, the cosmic structures it produces contain all colours — meaning, the operational consequences of the dew are visible and traceable. We can specify, in retrospect, what the dew did. The all colours seen in it claim is a positive structural feature: the dew is a generative source whose products are operationally legible.
radla is unspecifiable in principle. We cannot specify it in retrospect, because specification dissolves the structure. Whatever operational consequences emerge from radla (the unique-arrangements-of-MaH (gematria 45)-BaN (gematria 52), ultimately the Partzufim's specific identities), they do not trace back to specifiable features of radla in the way the dew traces back to A"A's head.
The contrast is structurally important because it shows that concealment in Klach has degrees. Some concealed structures (like the Dew of Bedolach) admit of post-hoc specification; some (like radla) do not. The methodology of investigation must respect both — and especially must not confuse them.
Op. 90 (A"A as the root of all Atzilut) presupposes Op. 89's framework: A"A is operational in a way radla is not, and the Dew of Bedolach is the cosmogonic seed of A"A's operational visibility.