What is the role of alladhī lam yuthqab in the onyx image?

Iṭnāb: Clarification after Ambiguity, Tawshīʿ, Repetition and Īghāl

• It refines the visual basis of the simile
• It removes all color resemblance between eye and onyx
• It renames the animals as a new species
• It exaggerates Ṣakhr’s guidance