 Clytemnestre is beside herself with grief and despair, conjuring up the god of thunder at the end of her apocalyptic invocations.Arcas comes to fetch her on behalf of Achille, who with his soldiers has interrupted the sacrifice; but then Ulysse arrives to reassure Clytemnestre that her daughter has been saved as the result of an unexpected miracle.At the moment that Achille and the other Greeks were facing each other for combat, the high priest Calchas revealed that, according to the oracle, Eriphile, the secret daughter of Hélène and Thésée, was also called "Iphigénie" and it was she whom the gods had required to be sacrificed.