The 'Atridan pair' were Agamemnon, king of Argos, and Menelaus, king of Sparta, the sons of Atreus.
LVI.

_Nereus_ was one of the chief sea-gods.
LXI.

Andromache was the wife of Hector.
LXIII.

Pyrrhus is the same as Neoptolemus in stanza xxxv.
LXXVI.

Creusa and Iulus were the wife and son of Aeneas.
LXXVII.