A Greek epic poem by Quintus Smyrnaeus continues the narration of Homer's Iliad with Posthomerica, more commonly known as The Fall of Troy.
Posthomerica means "after Homer", which sums up exactly what it is about. Continuing after the death of Hektor, it leads to the fall of Ilium. It is composed of fourteen books and was probably written within the 4th century.
Near the end of Book II, Nyx is mentioned as Eos mourns her murdered child Memnon.
"Thus as she (Dawn) [Eos] cried, the tears ran down her face
Immortal, like a river brimming aye:
Drenched was the dark earth round the corse. The Night [Nyx]
Grieved in her daughter's [Eos=Hemera] anguish, and the heaven
Drew over all his stars a veil of mist
And cloud, of love unto the Lady of Light. [Erigeneia]"
Close to the end of Book III Kalliope, the muse of epic poetry, speaks in comfort to Thetis, a nymph daughter of Nereus and wife of Peleus, who has lost her son Archilles and when she departs does Nyx make appearance.
"Then plunged the sun down into Ocean's [Okeanos] stream,
And sable-vestured Night [Nyx] came floating up
O'er the wide firmament, and brought her boon
Of sleep to sorrowing mortals."
Around the end of Book X as many mourn over the death of Paris, Oenone, a mountain nymph and Paris' first wife, despairs over turning him away to die and questions if she should follow after. Thus, leads to the following where Nyx is mentioned:
"So cried she, weeping, weeping piteously,
Remembering him whom death had swallowed up,
Wasting, as melteth wax before the flame
Yet secretly, being fearful lest her sire
Should mark it, or her handmaids till the night [Nyx]
Rose from broad Ocean [Okeanos], flooding all the earth
With darkness bringing men release from toil.
Then, while her father and her maidens slept,
She slid the bolts back of the outer doors,
And rushed forth like a storm-blast."
One thirds into Book XII Nyx is noted after Epeius has his dream about building the wooden Trojan horse.
"When rose the dawn [Eos], and thrust back kindly night [Nyx]
To Erebus [Erebos], and through the firmament streamed
Glad glory, then Epeius told his dream
To eager Argives -- all he saw and heard;
And hearkening joyed they with exceeding joy."
The very beginning of Book XIV Nyx is going back to her home as Eos leaves it.
"Then rose from Ocean [Okeanos] Dawn [Eos] the golden-throned
Up to the heavens; night [Nyx] into Chaos [Khaos] sank."
Internet sources:
OMACL - Quintus Smyrnaeus: The Fall of Troy