What was Eurydice like? Who knows? She seems a prop in the Orpheus myth, which is told any number of ways but always with one constant: Eurydice, dead of a viper’s bite, is a cipher. Her husband Orpheus, and his attempt to retrieve her from the Underworld, holds the spotlight. In this world premiere opera, composer Matthew Aucoin and playwright Sarah Ruhl allow Eurydice to step out of the shadows and claim her story. —L.J.