Complex sentence: Only at the second dinner party, when the king was sufficiently beguiled by her charms, did Esther reveal for the first time her identity as a Jew, and accused Haman of the plot to destroy her and her people.
Split into simpler sentences: Only at the second dinner party, when the king is sufficiently beguiled by her charms, does she reveal to the plot of Haman which involved the destruction of the Jewish people. She reveals, for the first time, her identity as a Jew and accuses Haman of the plot to destroy her and her people.