I like Scribo’s “aristocratic play”… But for the exact meaning I differ a bit in that I think the passage first quoted by Joel (Il. 20.321) more exact a parallel than those portraying a heroic death. Here it is in a bit more length:
Αὐτὰρ ἐπεὶ τό γ’ ἄκουσε Ποσειδάων ἐνοσίχθων,
βῆ ῥ’ ἴμεν ἄν τε μάχην καὶ ἀνὰ κλόνον ἐγχειάων,
ἷξε δ’ ὅθ’ Αἰνείας ἠδ’ ὃ κλυτὸς ἦεν Ἀχιλλεύς. (320)
αὐτίκα τῷ μὲν ἔπειτα κατ’ ὀφθαλμῶν χέεν ἀχλὺν
Πηλεΐδῃ Ἀχιλῆϊ· ὃ δὲ μελίην εὔχαλκον
ἀσπίδος ἐξέρυσεν μεγαλήτορος Αἰνείαο·
καὶ τὴν μὲν προπάροιθε ποδῶν Ἀχιλῆος ἔθηκεν,
Αἰνείαν δ’ ἔσσευεν ἀπὸ χθονὸς ὑψόσ’ ἀείρας.
Poseidon doesn’t strike Achilles down, just “blinds” him (or that’s how I understand it). But I guess the distinction isn’t even very important, the point is that it’s a poetic way of saying that an external agency robbed a person of his senses, whether fainting occurs or not. Darkness isn’t explicitly mentioned, and the αχλυς is removed in 341.
I checked LfgrE. I’m not going to misrepresent it by summarizing it, my German being what it is. Three scholia for αχλυς are given, one gives ἀορασία (this especially seems to support me), others σκοτιάς (whatever that means) and ἠ τῶν ὀφθαλμῶν σκότωσις. I’ll quote a bit:
Obwohl ἀ. bei Hom. meist ‘dichter (die Sicht verhindernder) Nebel’ oder ‘Dunkel’ ist (nur die zweite Bed., in versch. Schattierungen, auch später, aber rel. selten u. anscheinend meist poet.), wird man deshalb die primäre Bed. eher bei etwa ‘Dunst, Himmelstrübe[whatever that is]’, ‘Trübung des Lichtes, Glanzes, Auges’ (gegenüber θολός, θολερός ‘trübe’, vom Wasser) suchen.
This seems pretty close to my idea, though I might be tempted to leave the caveat (“Obwohl…”) out. The word occurs sometimes associated to darkness, sometimes to “mist”, what is the common denominator?
αιθηρ: That’s a funny word. Do you have an opinion as to whether it’s really connected to Αἰθίοψ (Ethiopian) as well? If it is, the evolution from “bright” to “black” is interesting indeed.