Norma (1974)

Oroveso, a Druid High Priest, gathers his people in a sacred forest and prays to their gods for help in vanquishing the Romans who have taken over Gaul. Unbeknownst to Oroveso, his daughter, Norma, a High Priestess, has for some time been the lover of Pollione, the leader of the Romans; she has, in fact, not only broken her sacred vow of chastity but has borne two children to the warrior. Norma uses her position to dissuade the Gauls from attacking the Romans, claiming that the gods have told her that the time is not favourable. Recorded at Théâtre Antique d'Orange, 1974

Unfortunately the movie Norma is not yet available on HBO Max.