καὶ μέγας Ἀντίοχος ἀπὸ τοῦδε κληθείς
And for this reason he was called Antiochus the Great.
The nominative signals a result or property as an argument, agreeing with the subject.
Result (with ‘to be appointed as…’ or ‘… to be called’)
With verbs such as αἱρέομαι ‘to be chosen as’, ὀνομάζομαι ‘to be called’ etc.
Property (with ‘to be regarded as…’)
Not only with the (passive) verbs νομίζομαι, ποιέομαι, τίθεμαι ‘to be regarded as’, but also with verbs such as φαίνομαι ‘to appear’.
In many cases this involves passive constructions in which the agreeing object is put in the nominative, in order to agree with the ‘original’ object, which has been converted to the subject. For example, the sentence ὁ Βάκχιος θεὸς νομίζεται ‘Bacchios is regarded as a god’ can be considered a passivisation of τὸν Βάκχιον θεὸν νομίζω ‘I regard Bacchios as a god’.
Like other agreeing arguments, for example the predicate NP, this agreeing argument never takes the article. As a consequence some grammars regard this nominative as a predicate NP.
ὁ Βάκχιος δὲ τίς; θεὸς νομίζεται;
Who is Bacchus? Is he regarded as a god?