The nominative (or accusative) neuter singular signals a loose apposition.
Some fixed expressions:
TBX καὶ τὸ δεινότατον and worst of all
τὸ δὲ πάντων θαυμαστότατον most astonishing of all
τὸ κεφάλαιον the main point is this
τὸ λεγόμενον as is generally said
τὸ μέγιστον the most important thing is this
It is usually impossible to tell whether these - invariably neuter singular - loose appositions are in the accusative or in the nominative.
ἱκέται δ’ ὄντες ἀγοραίου Διὸς | βιαζόμεσθα καὶ στέφη μιαίνεται | πόλει τ᾽ ὄνειδος καὶ θεῶν ἀτιμία
We, who are suppliants of Zeus Agoraeus, are being violently treated and our wreathes are being defiled, a disgrace to the city and an insult to the gods.