What is "fierrabras"

Fierrabras, 796, is a three-act German opera with spoken dialogue written by the composer Franz Schubert in 1823, to a libretto by , the general manager of the Theater am Kärntnertor (Vienna's Court Opera Theatre). Along with the earlier Alfonso und Estrella, composed in 1822, it marks Schubert's attempt to compose grand Romantic opera in German, departing from the Singspiel tradition.