Learn Italian: Che cosa disse l'oracolo all'eroe divino? - What did the oracle say to the divine hero?

Dire (to say) has a highly irregular passato remoto (historical past). It uses the root diss- for the "I", "he/she/it", and "they" forms (io dissi, lui/lei disse, loro dissero). The other forms use the root dic-, which actually comes from its original Latin infinitive: tu dicesti, noi dicemmo, voi diceste.

Why does the subject (l'oracolo) come after the verb (disse) in this sentence?

In Italian questions, it is very common to invert the subject and the verb, especially when starting with a question word like che cosa. You could technically say Che cosa l'oracolo disse..., but putting the subject after the verb sounds much more natural and fluid here.

Why do we need the combined preposition all' before eroe?

We need the preposition a (to) because the verb dire requires an indirect object when you specify who is being spoken to (dire qualcosa a qualcuno). Because eroe (hero) is a masculine noun starting with a vowel, it takes the definite article l'. Combining a + l' gives us all'.

Could I just say instead of ?